DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 280041
SWODY1
SPC AC 280039

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0739 PM CDT FRI APR 27 2007

VALID 280100Z - 281200Z

..THERE IS A SLGT RISK OF SVR TSTMS THIS EVENING OVER PARTS OF
SOUTHEAST VA AND NORTHEAST NC...

..EASTERN VA/NC...
BROAD UPPER TROUGH REMAINS OVER THE EASTERN STATES THIS
EVENING...WITH PRIMARY SURFACE COLD FRONT EXTENDING FROM EXTREME
SOUTHERN DE INTO CENTRAL NC. SCATTERED THUNDERSTORMS HAVE
RE-DEVELOPED ALONG THE FRONT DURING THE PAST COUPLE OF HOURS...WHERE
DEWPOINTS REMAIN IN THE MID 60S AND RELATIVELY STRONG LOW LEVEL
CONVERGENCE IS NOTED. THIS ACTIVITY MAY PERSIST FOR ANOTHER FEW
HOURS AS IT ADVANCES EASTWARD TOWARDS THE COAST. 00Z WAL SOUNDING
SHOWS OVER 40 KNOTS OF EFFECTIVE SHEAR...SUPPORTING A RISK OF
ORGANIZED MULTICELL OR SUPERCELL STORMS CAPABLE OF LARGE HAIL AND
DAMAGING WINDS.

..SOUTHWEST MO...
SMALL CLUSTER OF INTENSE THUNDERSTORMS HAS TRACKED FROM EASTERN KS
INTO SOUTHWEST MO THIS EVENING...AHEAD OF COMPACT UPPER SHORTWAVE
TROUGH. THESE STORMS HAVE PRODUCED NUMEROUS FUNNEL CLOUDS AND A
COUPLE OF TORNADOES...ALONG WITH LARGE HAIL. ACTIVITY IS MOVING
INTO A PROGRESSIVELY MORE STABLE ENVIRONMENT THAT WAS AFFECTED BY
EARLIER CONVECTION. THE SEVERE THREAT IS EXPECTED TO DIMINISH
RATHER RAPIDLY THROUGH 03Z IN THIS AREA.

..SOUTHWEST OK/NORTHWEST TX...
SURFACE OUTFLOW BOUNDARY FROM EARLIER CONVECTION EXTENDS ACROSS
SOUTHERN OK INTO NORTHWEST TX. ONSET OF DIURNAL COOLING AND
CONSIDERABLE CLOUDINESS ALONG THIS BOUNDARY ARE SUGGESTING THAT THE
POTENTIAL FOR CONVECTIVE INITIATION IS WANING. NEVERTHELESS...00Z
SOUNDINGS AND RECENT MODEL GUIDANCE CONTINUE TO INDICATE A LOW
PROBABILITY OF THUNDERSTORMS THIS EVENING ALONG THE BOUNDARY. IF
CONVECTION CAN FORM...STEEP MID LEVEL LAPSE RATES AND FAVORABLE
VERTICAL SHEAR PROFILES WOULD SUPPORT A RISK OF HIGH-BASED
SUPERCELLS CAPABLE OF LARGE HAIL.

.HART.. 04/28/2007

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MESO: Mesoscale Discussion 0608

ACUS11 KWNS 272333
SWOMCD
SPC MCD 272333
VAZ000-280100-

MESOSCALE DISCUSSION 0608
NWS STORM PREDICTION CENTER NORMAN OK
0633 PM CDT FRI APR 27 2007

AREAS AFFECTED...FAR ERN VA

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 272333Z - 280100Z

A SEVERE THREAT SHOULD CONTINUE ACROSS FAR ERN VA FOR 1 TO 2 HOURS.
HAIL AND STRONG GUSTY WINDS WILL LIKELY BE THE PRIMARY THREATS.
HOWEVER...THE SEVERE POTENTIAL SHOULD REMAIN TOO ISOLATED TO WARRANT
A WW ACROSS THE REGION EARLY THIS EVENING.

LATEST SFC ANALYSIS SHOWS A LOW ACROSS ERN VA WITH A COLD FRONT
EXTENDING SWWD ACROSS CNTRL VA INTO CNTRL NC. A COUPLE OF SEVERE
STORMS ARE LOCATED VERY NEAR THE SFC LOW IN AN AREA OF LOCALLY
ENHANCED INSTABILITY WHERE MLCAPE VALUES RANGE FROM 1000 TO 1200
J/KG. THE WAKEFIELD VA WSR-88D VWP SHOWS STRONG VERTICAL SHEAR WHICH
WILL BE SUFFICIENT TO CONTINUE A SUPERCELL THREAT ACROSS THE REGION
FOR A FEW MORE HOURS. ALTHOUGH MID-LEVEL LAPSE RATES ARE NOT THAT
STEEP...TEMPS ALOFT SHOWN ON OBJECTIVE ANALYSIS STILL APPEAR COLD
ENOUGH FOR A HAIL THREAT. THE POTENTIAL FOR STRONG GUSTY WINDS WILL
ALSO EXIST DUE TO STEEP LOW-LEVEL LAPSE RATES MAINLY SOUTH OF I-64.
SFC TEMPS ARE MUCH COOLER OVER THE CHESAPEAKE BAY AND THIS SHOULD
REDUCE THE SEVERE POTENTIAL AS STORMS MOVE GRADUALLY EWD EARLY THIS
EVENING.

.BROYLES.. 04/27/2007

..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...AKQ...

37117601 37107651 37457666 37807639 37927602 37757558
37557551 37167559

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MESO: Mesoscale Discussion 0607

ACUS11 KWNS 272240
SWOMCD
SPC MCD 272239
MOZ000-KSZ000-280015-

MESOSCALE DISCUSSION 0607
NWS STORM PREDICTION CENTER NORMAN OK
0539 PM CDT FRI APR 27 2007

AREAS AFFECTED...WRN MO

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 272239Z - 280015Z

AN ISOLATED SEVERE THREAT WILL LIKELY CONTINUE FOR AT LEAST ONE MORE
HOUR ACROSS FAR ERN KS WITH THE THREAT SPREADING INTO FAR WRN MO. A
BRIEF TORNADO OR TWO MAY OCCUR WITH THE STRONGER CELLS. HAIL AND
STRONG GUSTY WINDS MAY ALSO ACCOMPANY THE ACTIVITY. THE THREAT
SHOULD BE TOO BRIEF TO WARRANT A WW EARLY THIS EVENING ACROSS THE
REGION.

LATEST SFC ANALYSIS SHOWS A MOST AXIS EXTENDING NWD FROM ERN OK
ACROSS ERN KS INTO NW MO. A SFC TROUGH/WIND SHIFT IS LOCATED FROM
NEAR KANSAS CITY MO EXTENDING SWWD INTO NRN OK. ROTATING STORMS HAVE
DEVELOPED ALONG THIS SFC TROUGH IN A WEAKLY UNSTABLE BUT STRONGLY
SHEARED ENVIRONMENT. AMPLE SPEED SHEAR EXISTS ON REGIONAL PROFILERS
FOR SUPERCELL STORMS ALTHOUGH SFC WINDS ARE VEERED ACROSS MOST OF
THE MD AREA. AN ISOLATED TORNADO THREAT STILL MAY OCCUR WITH THE
STRONGER ROTATING STORMS. IN ADDITION...STEEP MID-LEVEL LAPSE RATES
AND UNIDIRECTIONAL WIND PROFILES BELOW 850 MB SHOWN ON FORECAST
SOUNDINGS LATE THIS AFTERNOON MAY RESULT IN A THREAT FOR HAIL AND
STRONG GUSTY WINDS OVER THE NEXT FEW HOURS.

.BROYLES.. 04/27/2007

..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...SGF...EAX...

37319416 37439459 38089463 38809460 39109441 39079395
38539374 37579383

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WATCHES: Severe Thunderstorm Watch - Number 197

WWUS20 KWNS 272035
SEL7
SPC WW 272035
MDZ000-NCZ000-VAZ000-CWZ000-272300-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH - NUMBER 197
NWS STORM PREDICTION CENTER NORMAN OK
435 PM EDT FRI APR 27 2007

THE NWS STORM PREDICTION CENTER HAS CANCELLED
SEVERE THUNDERSTORM WATCH NUMBER 197 ISSUED AT 1200 PM EDT FOR PORTIONS OF

MARYLAND
NORTH CAROLINA
VIRGINIA
COASTAL WATERS

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DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 271938
SWODY1
SPC AC 271936

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0236 PM CDT FRI APR 27 2007

VALID 272000Z - 281200Z

..THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTN/EVE ACROSS PARTS
OF THE MID ATLANTIC COAST STATES....

..ATLANTIC SEABOARD...
INCREASING DOWNSLOPE FLOW TO THE LEE OF THE CENTRAL APPALACHIANS IS
ONGOING...AS STRONGER FORCING ASSOCIATED WITH INITIAL UPPER IMPULSE
LIFTS NORTHEAST OF THE LOWER GREAT LAKES/NORTHERN AND CENTRAL
APPALACHIANS REGION. HOWEVER...AS NEXT IMPULSE SHIFTS TOWARD MID
ATLANTIC COASTAL AREAS...ASSOCIATED LARGE-SCALE ASCENT COULD STILL
AID CONVECTIVE DEVELOPMENT ACROSS PARTS OF EASTERN NORTH
CAROLINA/SOUTHEAST VIRGINIA. BOUNDARY LAYER ACROSS THIS REGION IS
EXPECTED TO REMAIN MOIST AND POTENTIALLY UNSTABLE INTO EARLY
EVENING...AND DEEP LAYER SHEAR BENEATH 40-50 KT CYCLONIC 500 MB FLOW
IS SUPPORTIVE OF SUPERCELLS. THE STRONGER LOW-LEVEL JET IS IN THE
PROCESS OF SHIFTING NORTHEAST OF MID ATLANTIC COASTAL AREAS...BUT
LOW-LEVEL HODOGRAPHS MAY REMAIN FAIRLY LARGE THROUGH THE PEAK
HEATING HOURS ACROSS PARTS OF NORTHEAST NORTH CAROLINA/EXTREME
SOUTHEAST VIRGINIA...WHERE AN ISOLATED TORNADO APPEARS POSSIBLE.

..CENTRAL/SOUTHERN PLAINS...
A VIGOROUS SHORT WAVE TROUGH CONTINUES TO DIG ACROSS THE CENTRAL
PLAINS INTO THE OZARK PLATEAU. COLD CORE AND STRONGER MID-LEVEL
FORCING ASSOCIATED WITH THIS SYSTEM STILL APPEARS LIKELY TO REMAIN
DISPLACED WELL TO THE NORTH OF BETTER RETURN FLOW. AND...THIS IS
EXPECTED TO BE A LIMITING FACTOR WITH RESPECT TO CONVECTIVE
POTENTIAL.

MOISTENING ABOVE THE BOUNDARY LAYER...ASSOCIATED WITH LOW-LEVEL
ISENTROPIC ASCENT TO THE SOUTH/SOUTHWEST OF UPPER IMPULSE...IS
EXPECTED TO CONTINUE TO PROVIDE THE FORCING FOR THE PRIMARY
CONVECTIVE DEVELOPMENT. THIS IS IN THE PROCESS OF BECOMING FOCUSED
NEAR THE RED RIVER...WHERE STRONGEST STORMS ARE ANTICIPATED LATE
THIS AFTERNOON AND EVENING. SHEAR IN THE CLOUD BEARING LAYER SEEMS
MARGINALLY SUPPORTIVE OF UPDRAFT ROTATION...WHICH MAY PROMOTE THE
RISK FOR HAIL IN AN ENVIRONMENT WITH MOST UNSTABLE CAPE AT OR ABOVE
500 J/KG. IT SEEMS POSSIBLE THAT CONVECTION COULD AT LEAST BRIEFLY
BECOME ROOTED IN THE BOUNDARY LAYER BEFORE NIGHTFALL...SOUTH OF THE
CHILDRESS/ WICHITA FALLS AREA...WHERE...LOCALLY...MIXED LAYER CAPE
COULD APPROACH 1000 J/KG. IF THIS OCCURS...BETTER VERTICAL SHEAR
FOR BOUNDARY LAYER BASED STORMS MAY SUPPORT AN ISOLATED SUPERCELL
BEFORE ACTIVITY WEAKENS WITH LOSS OF DAYTIME HEATING.

..SOUTHERN PLATEAU/ROCKIES...
TO THE NORTHEAST OF A CLOSED LOW BECOMING CUT-OFF NEAR THE BAJA
SPUR...DEEPENING CONVECTION IS ALREADY EVIDENT ALONG PARTS OF THE
MOGOLLON RIM AND MOUNTAINS OF SOUTHWEST NEW MEXICO. THIS APPEARS
ROUGHLY BETWEEN STRONGER MID-LEVEL SUBSIDENCE ASSOCIATED WITH UPPER
RIDGE...AND STRONGER MID-LEVEL UPWARD VERTICAL MOTION ASSOCIATED
WITH CUT-OFF LOW. BUT...EVEN IF MORE FAVORABLE FORCING IS SOUTH OF
REGION...FURTHER HEATING MAY SUPPORT A FEW THUNDERSTORMS ALONG THE
HIGHER TERRAIN LATE THIS AFTERNOON.

..PACIFIC COAST STATES...
STRONG HEATING IS ALSO CONTRIBUTING TO DESTABILIZATION ALONG THE
NORTHERN SIERRA NEVADA INTO THE SOUTHERN CASCADES. AS UPPER RIDGE
AXIS SHIFTS TO THE EAST...LOW/MID-LEVEL MOISTENING MAY SUPPORT
ISOLATED TO WIDELY SCATTERED THUNDERSTORMS LATE THIS AFTERNOON AND
EVENING. MID-LEVEL HEIGHT FALLS COULD ALSO ALLOW CONVECTIVE
DEVELOPMENT INTO PARTS OF CENTRAL/EASTERN OREGON BY THIS EVENING.

.KERR.. 04/27/2007

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MESO: Mesoscale Discussion 0606

ACUS11 KWNS 271933
SWOMCD
SPC MCD 271933
DEZ000-MDZ000-VAZ000-NCZ000-272130-

MESOSCALE DISCUSSION 0606
NWS STORM PREDICTION CENTER NORMAN OK
0233 PM CDT FRI APR 27 2007

AREAS AFFECTED...ERN NC...SERN VA...VA CAPE

CONCERNING...SEVERE THUNDERSTORM WATCH 197...

VALID 271933Z - 272130Z

THE SEVERE WEATHER THREAT FOR VALID PORTIONS OF SEVERE THUNDERSTORM
WATCH 197 CONTINUES.

MID/UPR-LEVEL SPEED MAX MOVING THROUGH THE MID-ATLANTIC REGION HAS
SUPPORTED SCATTERED STRONG TSTMS ACROSS ERN NC INTO SERN VA THIS
AFTN. IN WAKE OF THIS IMPULSE...RUC SOUNDINGS SUGGEST THAT
SUBSIDENCE/MID-LVL WARMING WAS SPREADING NEWD AND HAS...OR
WILL...BECOME SOMEWHAT UNSUPPORTIVE FOR SUSTAINED SEVERE TSTMS BY
EARLY EVE. UNTIL THEN...TSTM CLUSTERS/SHORT-LINE SEGMENTS WILL
LIKELY FAVOR NERN NC INTO SERN VA FOR A FEW MORE HOURS. DAMAGING
WINDS AND PERHAPS HAIL WILL ACCOMPANY THE STRONGER STORMS. AN
UPSTREAM IMPULSE ROUNDING THE BASE OF THE GRTLKS TROUGH WILL SWING
NEWD INTO THE SERN STATES/CAROLINAS LATER THIS EVE. BY
THEN...HOWEVER...THE INCREASING DOWNSLOPE LOW-LVL FLOW SHOULD OFFSET
THE LARGER SCALE ASCENT AND MINIMIZE THE SVR RISKS DURING THE
EVENING HOURS.

.RACY.. 04/27/2007

..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...PHI...AKQ...MHX...LWX...RAH...RNK...

38857647 38787540 38417472 37157554 36897570 36187589
35647573 34957647 34817725 35057869 35857925

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DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 271715
SWODY2
SPC AC 271714

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1214 PM CDT FRI APR 27 2007

VALID 281200Z - 291200Z

..NO SVR TSTM AREAS FORECAST...

..SYNOPSIS...
AMPLIFICATION IN THE LARGE-SCALE UPPER FLOW NOW UNDERWAY ACROSS THE
U.S. WILL PERSIST INTO SATURDAY. BUT...MODELS INDICATE THAT THE
PATTERN WILL REMAIN GENERALLY PROGRESSIVE. EASTERN UPPER TROUGH IS
PROGGED TO BEGIN ADVANCING OFF ATLANTIC COASTAL AREAS BY LATE
SATURDAY NIGHT...AS UPSTREAM RIDGE SHIFTS EAST OF THE INTERMOUNTAIN
WEST. SOME SUPPRESSION/BROADENING OF THE UPPER RIDGE IS FORECAST TO
OCCUR IN RESPONSE TO IMPULSES MIGRATING AROUND ITS NORTHERN
PERIPHERY...INCLUDING ONE TOPPING AND DIGGING TO THE LEE OF ITS
CREST...ACROSS THE CENTRAL CANADIAN PROVINCES...AND ANOTHER LIFTING
INTO PACIFIC COASTAL AREAS BY 12Z SUNDAY. MORE UNCERTAINTY EXISTS
CONCERNING CUT-LOW...NOW DEVELOPING INTO AREAS NEAR/EAST OF THE BAJA
SPUR. BUT...LATEST GFS/ECMWF AND NAM ALL SUGGEST THAT A
NORTHEASTWARD ACCELERATION ACROSS THE NORTHWESTERN MEXICAN PLATEAU
COULD OCCUR LATE IN THE PERIOD.

..INTERMOUNTAIN WEST/ROCKIES/HIGH PLAINS...
IN THE WAKE OF THE EASTERN UPPER TROUGH...LOW-LEVEL RIDGING WILL
MINIMIZE CONVECTIVE POTENTIAL ACROSS MOST AREAS EAST OF THE ROCKIES.
HOWEVER...LINGERING MOISTURE IN THE LOWER RIO GRANDE VALLEY WILL
ADVECT UPSLOPE AROUND THE SOUTHWESTERN PERIPHERY OF THE RIDGE...INTO
HIGHER TERRAIN OF THE MEXICAN PLATEAU/SOUTHWEST TEXAS AND THE
SOUTHERN ROCKIES. LOW/MID-LEVEL MOISTURE WILL BE MORE LIMITED
NORTHWARD THROUGH THE ROCKIES INTO THE NORTHERN INTERMOUNTAIN
REGION. BUT...STRONG HEATING ACROSS THE HIGHER TERRAIN BENEATH
UPPER RIDGE IS EXPECTED TO BE SUPPORTIVE OF SUFFICIENT
DESTABILIZATION FOR AT LEAST WEAK SCATTERED AFTERNOON/EVENING
THUNDERSTORM ACTIVITY.

LARGE-SCALE ISENTROPIC ASCENT ON NORTHERN FRINGE OF THE UPPER RIDGE
MAY ENHANCE CONVECTIVE DEVELOPMENT LATE SATURDAY AFTERNOON/EVENING
ACROSS PARTS OF THE NORTHERN INTERMOUNTAIN REGION/ROCKIES...WITH
HIGH-BASED/ELEVATED ACTIVITY PERHAPS SPREADING EASTWARD INTO PARTS
OF THE NORTHERN PLAINS SATURDAY NIGHT. FARTHER SOUTH...STRONGER
DESTABILIZATION AND FORCING ASSOCIATED WITH THE CUT-OFF LOW SEEMS TO
FAVOR THE MEXICAN PLATEAU FOR STRONGEST/MOST NUMEROUS
STORMS...UNLESS SYSTEM LIFTS OUT MORE RAPIDLY THAN ANTICIPATED.
HOWEVER...AT LEAST ISOLATED VIGOROUS STORMS ARE POSSIBLE ACROSS THE
MOUNTAINS OF SOUTHWEST TEXAS...WHERE MODELS INDICATE MODERATE FLOW
FIELDS VEERING STRONGLY WITH HEIGHT...CONTRIBUTING TO SUFFICIENT
SHEAR FOR AT LEAST BRIEF UPDRAFT ROTATION.

..FLORIDA PENINSULA...
LOW-LEVEL CONVERGENCE MAY BECOME FOCUSED SATURDAY AHEAD OF COLD
FRONT...ALONG SEA BREEZES ACROSS SOUTHEAST COASTAL AREAS. THIS MAY
BECOME SUFFICIENT FOR ISOLATED THUNDERSTORM ACTIVITY IN MOIST
..POTENTIALLY UNSTABLE ENVIRONMENT. BUT...MODEL FORECAST SOUNDINGS
SUGGEST THAT MID-LEVEL INHIBITION WILL BE CONSIDERABLE ...PROBABLY
MINIMIZING CONVECTIVE POTENTIAL.

.KERR.. 04/27/2007

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DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 271632
SWODY1
SPC AC 271630

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1130 AM CDT FRI APR 27 2007

VALID 271630Z - 281200Z

..THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON FROM THE ERN
CAROLINAS INTO THE LOWER CHESAPEAKE REGION...

..MID ATLANTIC REGION THIS AFTERNOON...
MORNING WATER VAPOR IMAGERY SHOWS A COMPLEX MID LEVEL LOW OVER THE
GREAT LAKES...WITH SEVERAL SMALLER SCALE SPEED MAXIMA ROTATING
AROUND THE S/SE PERIPHERY OF THE LOW. ONE SUCH IMPULSE WILL MOVE
FROM N GA ACROSS THE CAROLINAS TO SE VA BY THIS EVENING...AS A WEAK
SURFACE COLD FRONT AND PRE-FRONTAL TROUGH MOVE EWD TO THE COAST BY
LATER TONIGHT. THESE SURFACE BOUNDARIES AND THE APPROACHING MID
LEVEL WAVE WILL PROVIDE A FAVORABLE ENVIRONMENT FOR THUNDERSTORM
DEVELOPMENT FROM THE CAROLINAS INTO VA THIS AFTERNOON.

REGIONAL 12Z SOUNDINGS REVEALED THE POTENTIAL FOR MODEST INSTABILITY
WITH DAYTIME HEATING /AFTERNOON MLCAPE VALUES OF 500-1000 J/KG BASED
ON SURFACE TEMPERATURES NEAR 80 F WITH MID 60S DEWPOINTS/...AND A
CAP NEAR 700 MB THAT SHOULD ERODE GRADUALLY WITH LOW-LEVEL MIXING
AND LOW-MID LEVEL ASCENT. IT APPEARS THAT THE WIDESPREAD CLOUDS AND
EARLY CONVECTIVE DEVELOPMENT IN SE VA SHOULD LIMIT THE NWD EXTENT OF
THE INSTABILITY THIS AFTERNOON. MEANWHILE...WARM SECTOR WIND
PROFILES SHOULD BE CHARACTERIZED BY LARGELY UNIDIRECTIONAL FLOW WITH
MODEST SPEED SHEAR THROUGH THE LOW-MID LEVELS...WHICH SHOULD SUPPORT
A FEW SUPERCELLS AND/OR SHORT BOWING SEGMENTS CAPABLE OF PRODUCING
DAMAGING WINDS AND PERHAPS A TORNADO OR TWO. OTHERWISE...MARGINALLY
SEVERE HAIL MAY ACCOMPANY THE MORE INTENSE STORMS THIS AFTERNOON.

..W TX/OK AREA THIS AFTERNOON/EVENING...
A PRONOUNCED MID LEVEL SHORTWAVE OVER SRN NEB/NRN KS WILL PROGRESS
SEWD TO MO/NRN AR BY EARLY TONIGHT. THE STRONGEST FORCING FOR
ASCENT WILL GENERALLY BE CONFINED TO AREAS FROM ERN KS/NE OK
NEWD...WHILE A BELT OF WAA FROM THE WSW SPREADS SEWD ACROSS OK
DURING THE DAY. REGIONAL 12Z SOUNDINGS SHOW ONLY LIMITED POTENTIAL
FOR INSTABILITY WITH THE RICHER LOW-LEVEL MOISTURE AND STEEPER MID
LEVEL LAPSE RATES CONFINED TO AREAS OF S AND W TX. MEAN BOUNDARY
LAYER DEWPOINTS ARE UNLIKELY TO EXCEED THE LOW-MID 50S FROM CENTRAL
TX INTO OK...AND ONLY WEAK INSTABILITY IS EXPECTED WITH AFTERNOON
SURFACE TEMPERATURES OF 75-80 F FROM SW OK INTO NW TX. IF SURFACE
HEATING/MIXING CAN SUFFICIENTLY WEAKEN THE CAP ALONG THE SURFACE
BOUNDARY AND IN THE WAKE OF THE EARLY ELEVATED STORMS...ISOLATED
HIGH-BASED SUPERCELLS WILL BE POSSIBLE. HOWEVER...CONFIDENCE IN
SURFACE-BASED DEVELOPMENT IS LOW AND THE OVERALL SEVERE THREAT
APPEARS TOO MARGINAL TO WARRANT MORE THAN LOW SEVERE PROBABILITIES.

FARTHER SW...STRONGER HEATING/DEEPER MIXING MAY ALLOW THE CAP TO
ERODE SUFFICIENTLY FOR ISOLATED THUNDERSTORM DEVELOPMENT THIS
AFTERNOON ALONG THE WEAK INVERTED TROUGH/COLD FRONT INTO W TX.
LIMITED MOISTURE AND WEAKER VERTICAL SHEAR COMPARED TO AREAS FARTHER
N SUGGEST THAT ANY SEVERE STORM THREAT IN THIS AREA WILL ALSO REMAIN
ISOLATED/MARGINAL.

.THOMPSON/GRAMS.. 04/27/2007

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WATCHES: Severe Thunderstorm Watch Number 197

WWUS20 KWNS 271602
SEL7
SPC WW 271602
MDZ000-NCZ000-VAZ000-CWZ000-272300-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 197
NWS STORM PREDICTION CENTER NORMAN OK
1200 PM EDT FRI APR 27 2007

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

EASTERN SHORE OF MARYLAND
EASTERN NORTH CAROLINA
SOUTHEAST VIRGINIA
COASTAL WATERS

EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM NOON UNTIL 700
PM EDT.

HAIL TO 1.5 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70
MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 80
STATUTE MILES EAST AND WEST OF A LINE FROM 10 MILES NORTH
NORTHWEST OF WALLOPS VIRGINIA TO 25 MILES WEST OF JACKSONVILLE
NORTH CAROLINA. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU7).

REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY
DO PRODUCE TORNADOES.

DISCUSSION...SCATTERED THUNDERSTORMS WILL LIKELY INCREASE IN
COVERAGE/INTENSITY THIS AFTERNOON AS THE LOW LEVELS DESTABILIZE AND
A WEAK SHORTWAVE TROUGH APPROACHES NC/VA FROM SC. THE COMBINATION
OF MODERATE INSTABILITY AND LARGELY UNIDIRECTIONAL WIND PROFILES
WILL SUPPORT BOTH BOWING SEGMENTS AND MORE ISOLATED SUPERCELLS.
DAMAGING WINDS SHOULD BE THE MAIN SEVERE THREAT...WHILE LARGE HAIL
WILL ALSO BE POSSIBLE WITH THE STRONGEST STORMS.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 450. MEAN STORM
MOTION VECTOR 24035.

..THOMPSON

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MESO: Mesoscale Discussion 0605

ACUS11 KWNS 271529
SWOMCD
SPC MCD 271529
NCZ000-VAZ000-SCZ000-271630-

MESOSCALE DISCUSSION 0605
NWS STORM PREDICTION CENTER NORMAN OK
1029 AM CDT FRI APR 27 2007

AREAS AFFECTED...SERN VA...ERN NC

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 271529Z - 271630Z

LATEST WV IMAGERY CLEARLY DEPICTS A WEAK SHORTWAVE TROUGH LIFTING
NEWD ACROSS SC TOWARD MIDDLE ATLANTIC REGION. RADAR TRENDS SUPPORT
THIS FEATURE WITH DEEPENING CONVECTION OVER SC...AND ALONG AN AXIS
OF DEEPER CONFLUENCE STRETCHING ACROSS CNTRL NC INTO SERN VA.
THUNDERSTORMS ARE BEGINNING TO DEVELOP OVER SERN VA WITHIN THIS
ZONE...AND SHOULD SOON DEVELOP SWWD AS SHORTWAVE ENHANCES
CONVERGENCE. AS TEMPERATURES WARM INTO THE LOWER 80S THERE IS
GREATER CONFIDENCE IN ROBUST UPDRAFT DEVELOPMENT. SHEAR VECTORS
FAVOR ORGANIZED LINE SEGMENTS WITH POSSIBLE ISOLATED SUPERCELLS.
DAMAGING WINDS ARE THE MOST LIKELY SEVERE THREAT.

.DARROW.. 04/27/2007

..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...AKQ...MHX...RAH...ILM...

34637948 36317831 37927642 37237558 35077556 33807806

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DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 271252
SWODY1
SPC AC 271250

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0750 AM CDT FRI APR 27 2007

VALID 271300Z - 281200Z

..THERE IS A SLGT RISK OF SVR TSTMS FOR THE MID ATLANTIC STATES...

..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF OK AND
NORTHERN/WESTERN TX...

..SYNOPSIS...
WATER VAPOR IMAGERY FEATURES UPPER LOW CENTERED OVER MI EARLY THIS
MORNING...WITH THIS FEATURE FORECAST TO WEAKEN/LIFT NORTHEASTWARD
INTO EASTERN CANADA TODAY. WITHIN THE BROADER/EVOLVING EASTERN
STATES UPPER TROUGH...SEVERAL TRAILING SHORTWAVE IMPULSES ARE
FORECAST TO CROSS THE PLAINS AND TENNESSEE VALLEY/MID ATLANTIC
STATES AMIDST A MODERATELY STRONG BELT OF MID LEVEL FLOW. AT THE
SURFACE EARLY THIS MORNING...AN OCCLUDED/COLD FRONT WAS ANALYZED
ROUGHLY NORTH-SOUTH ALONG THE APPALACHIANS...ARCING FROM A 1002 MB
SURFACE LOW IN EASTERN LOWER MI INTO GA/FL PANHANDLE. A WEST-EAST
ORIENTED WARM FRONT WAS ANALYZED ACROSS VA...DEMARCATING 60S F
DEWPOINTS TO THE SOUTH OF THE FRONT ACROSS THE CAROLINAS. IN THE
WEST...BROAD UPPER RIDGE WILL AMPLIFY OVER MUCH OF THE WESTERN
STATES BENEATH A STRONG PACIFIC JET NOSING INTO THE PACIFIC
NORTHWEST AND WESTERN CANADIAN PROVINCES.

..MID ATLANTIC STATES THROUGH EARLY EVENING...
PRIMARY COLD FRONT WILL PUSH EASTWARD FROM THE SPINE OF THE
APPALACHIANS TOWARD THE MID ATLANTIC SEABOARD THROUGH EARLY
EVENING...WHILE THE WARM FRONT GRADUALLY LIFTS NORTHWARD ACROSS THE
DELMARVA. AHEAD OF THE COLD FRONT...GRADUAL EXIT OF EXISTING EARLY
MORNING CONVECTION AND SURGING MID LEVEL DRY SLOT WILL ALLOW FOR
SOME POCKETS OF STRONGER DAYTIME HEATING. COMBINED WITH DEWPOINTS IN
THE 60S F...AMPLE INSTABILITY WILL EXIST FOR SCATTERED STRONG/SEVERE
STORMS FROM LATE MORNING THROUGH EARLY EVENING...ESPECIALLY FROM THE
DELMARVA VICINITY TO THE COASTAL PLAIN OF THE CAROLINAS. NAM/NAMKF
FORECAST SOUNDINGS SUGGEST MLCAPE VALUES AROUND 1000 J/KG IN THE
AMBIENT WARM SECTOR...MAXIMIZED ACROSS SOUTHEAST VA INTO THE COASTAL
AREAS OF NC/SC. STRONG VERTICAL SHEAR WILL SUPPORT THE EVOLUTION OF
SOME SEMI-DISCRETE AND/OR LINE EMBEDDED SUPERCELLS THIS
AFTERNOON...WITH DAMAGING WINDS/LARGE HAIL AND A FEW TORNADOES
POSSIBLE.

..OK AND WESTERN/NORTHERN TX THIS AFTERNOON/EVENING...
WITH SHORTWAVE TROUGH AND ASSOCIATED WEAK COLD FRONT/TROUGH
ADVANCING SOUTHEASTWARD ACROSS THE SOUTH CENTRAL PLAINS
TODAY...ASSOCIATED LARGE SCALE ASCENT IS EXPECTED TO LEAD TO
INCREASING THUNDERSTORM COVERAGE ACROSS MUCH OF OK AND PORTIONS OF
NORTHERN/WESTERN TX THROUGH THE AFTERNOON. 12Z OBSERVED SOUNDINGS
SUGGEST ONLY LIMITED MOISTURE WILL GRADUALLY RETURN NORTHWESTWARD
ACROSS TX/OK AROUND THE SURFACE HIGH CENTERED OVER THE ARKLATEX.
ALTHOUGH SURFACE DEWPOINTS WILL GENERALLY BE LIMITED TO THE LOWER
50S F...AFTERNOON HEATING WILL LEAD TO MODEST CONVECTIVE INSTABILITY
WITH MLCAPES UP TO 750 J/KG. FORECAST SOUNDINGS DEPICT STRONGLY
VEERING WIND PROFILES WITH EFFECTIVE BULK SHEAR GREATER THAN 40 KT.
THIS WILL SUPPORT SOME SUPERCELL STRUCTURES WITH A RISK OF LARGE
HAIL...AS WELL AS THE POTENTIAL FOR STRONG WIND GUSTS AMIDST A WELL
MIXED BOUNDARY LAYER.

.GUYER/EDWARDS.. 04/27/2007

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DAY48SVR: Nws Storm Prediction Center Norman Ok

ACUS48 KWNS 270833
SWOD48
SPC AC 270832

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0332 AM CDT FRI APR 27 2007

VALID 301200Z - 051200Z

..DISCUSSION...

PATTERN CONTINUES TO CHANGE DURING THE DAY 4 AND DAY 5 PERIOD AS
SEVERAL SHORTWAVE TROUGHS MOVE NEWD FROM THE SRN PLATEAU REGION INTO
THE MID MS VALLEY AHEAD OF BROAD VORTEX MOVING OUT OF THE GULF OF
ALASKA TOWARDS THE PACIFIC NORTHWEST. THE ECMWF IS A BIT SLOWER
THAN THE GFS AFTER DAY 5 AS A HIGH AMPLITUDE TROUGH MOVES INTO THE
WRN U.S. AND ANOTHER TROUGH MOVES SEWD OUT OF HUDSON BAY TOWARDS THE
NERN U.S. ESSENTIALLY CREATING A HIGH AMPLITUDE OMEGA PATTERN OVER
NORTH AMERICA. THE GFS CREATES A SERIES OF LOW PRESSURE SYSTEMS
THAT MOVE NNEWD THRU THE NRN HIGH PLAINS WITH THE MAIN FEATURE
DEVELOPING BY THE END OF THIS PERIOD SOMEWHERE BETWEEN ERN CO AND
ERN MT. THUS...THE WIDE RANGE OF SOLUTIONS AT THIS TIME GIVEN BY
THE EXTENDED TRENDS GIVES A LOW PREDICTABILITY TO INCLUDE A SEVERE
RISK.

.MCCARTHY.. 04/27/2007

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DAY3SVR: Nws Storm Prediction Center Norman Ok

ACUS03 KWNS 270747
SWODY3
SPC AC 270745

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0245 AM CDT FRI APR 27 2007

VALID 291200Z - 301200Z

..NO SVR TSTM AREAS FORECAST...

..SYNOPSIS...
MID/UPPER LEVEL RIDGING WILL EXTEND FROM THE WRN SECTIONS OF THE
LOWER MS VALLEY INTO THE MID MS VALLEY EFFECTIVELY TAKING THE MAIN
BAND OF THE WESTERLIES ACROSS THE NRN TIER OF STATES THEN SEWD OVER
THE LOWER GREAT LAKES AND THE NRN MID ATLANTIC REGION. MID/UPPER
LEVEL LOW OVER NWRN MEXICO DURING THE DAY 2 PERIOD WILL GRADUALLY
WEAKEN AND DRIFT ENEWD INTO EXTREME W TX/SRN PLATEAU REGION BY
30/12Z.

..AREAS OF W TX AND THE RIO GRANDE VALLEY...

FLOW OF LOW LEVEL MOISTURE IS PROJECTED TO BE NWD THRU THE ERN RANGE
OF THE MEXICAN MOUNTAINS/HIGH PLAINS INTO W TX SUNDAY. MODELS
INDICATE SUFFICIENT LOW LEVEL JET OF 30-40 KT EXTENDING NWD OVER THE
TX BIG BEND REGION COUPLED WITH A SWLY 50 KT MID LEVEL JET.
THUS...THERE WILL BE SUFFICIENT SHEAR TO SUPPORT THUNDERSTORMS...BUT
CONSIDERABLE CLOUD COVER IS EXPECTED TO LIMIT INSTABILITY WHERE
MUCAPES ARE PROGGED TO BE AROUND 500 J/KG. THUS...A FEW STRONG
THUNDERSTORMS COULD BE ASSOCIATED WITH THE WEAK MID/UPPER LOW...BUT
THESE STORMS ARE EXPECTED TO REMAIN BELOW SEVERE DUE TO THE LACK OF
SUFFICIENT INSTABILITY.

.MCCARTHY.. 04/27/2007

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DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 270615
SWODY1
SPC AC 270613

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0113 AM CDT FRI APR 27 2007

VALID 271200Z - 281200Z

..THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE MID ATLANTIC
STATES...

..THERE IS A SLGT RISK OF SVR TSTMS FOR PORTIONS OF OK AND NORTHERN
TX...

..SYNOPSIS...
INITIAL UPPER LOW OVER THE WESTERN GREAT LAKES IS FORECAST TO
WEAKEN/LIFT NORTHEASTWARD INTO EASTERN CANADA TODAY...WHILE SEVERAL
TRAILING SHORTWAVE IMPULSES CROSSING THE PLAINS AND TENNESSEE
VALLEY/MID ATLANTIC STATES REINFORCE AN EVOLVING BROAD UPPER TROUGH
OVER THE EASTERN THIRD OF THE COUNTRY. IN THE WEST...BROAD UPPER
RIDGE WILL AMPLIFY OVER MUCH OF THE WESTERN STATES BENEATH STRONG
PACIFIC JET NOSING INTO THE PACIFIC NORTHWEST/WESTERN CANADA.

..MID ATLANTIC STATES THROUGH EARLY EVENING...
PRIMARY COLD FRONT WILL PUSH EASTWARD FROM THE SPINE OF THE
APPALACHIANS TOWARD THE MID ATLANTIC SEABOARD THROUGH EARLY EVENING.
AHEAD OF THE FRONT...POCKETS OF STRONGER DAYTIME HEATING AND
DEWPOINTS IN THE 60S F WILL CONTRIBUTE TO AMPLE INSTABILITY FOR
SCATTERED STRONG/SEVERE STORMS FROM LATE MORNING THROUGH EARLY
EVENING...ESPECIALLY FROM THE DELMARVA VICINITY TO THE
PIEDMONT/COASTAL AREAS OF THE CAROLINAS. NAM/NAMKF FORECAST
SOUNDINGS SUGGEST MLCAPE VALUES OF 750-1000 J/KG IN THE AMBIENT WARM
SECTOR. VERTICAL SHEAR PROFILES WILL SUPPORT THE EVOLUTION OF SOME
SEMI-DISCRETE AND/OR LINE EMBEDDED SUPERCELLS...WITH LARGE
HAIL/DAMAGING WINDS AND A FEW TORNADOES POSSIBLE.

..OK AND WESTERN/NORTHERN TX THIS AFTERNOON/EVENING...
WITH SHORTWAVE TROUGH EXPECTED TO CROSS THE SOUTH CENTRAL PLAINS
TODAY...ASSOCIATED LARGE SCALE ASCENT IS EXPECTED TO LEAD TO
INCREASING THUNDERSTORM COVERAGE ACROSS MUCH OF OK AND PORTIONS OF
NORTHERN/WESTERN TX THROUGH THE AFTERNOON HOURS. IN THE WAKE OF THE
EAST COAST UPPER TROUGH/COLD FRONT...MODEST BOUNDARY MOISTURE WILL
GRADUALLY RETURN NORTHWESTWARD ACROSS TX/OK AROUND SURFACE HIGH
CENTERED OVER THE ARKLATEX. ALTHOUGH SURFACE DEWPOINTS WILL
GENERALLY BE LIMITED TO THE MIDDLE 50S F OR LESS...AFTERNOON HEATING
WILL LEAD TO MODEST CONVECTIVE INSTABILITY WITH MLCAPES UP TO 1000
J/KG. FORECAST SOUNDINGS DEPICT STRONGLY VEERING WIND PROFILES WITH
EFFECTIVE BULK SHEAR GREATER THAN 40 KT...SUPPORTIVE OF SOME
SUPERCELLS WITH A RISK OF LARGE HAIL AND STRONG WIND GUSTS.

.GUYER/CARBIN.. 04/27/2007

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DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 270535
SWODY2
SPC AC 270533

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1233 AM CDT FRI APR 27 2007

VALID 281200Z - 291200Z

..NO SVR TSTM AREAS FORECAST...

..SYNOPSIS...
MID/UPPER LEVEL TROUGH OVER THE ERN U.S. WILL SLOWLY SHIFT EWD
DURING THE PERIOD WITH MID/UPPER LEVEL RIDGE OVER THE INTERMOUNTAIN
AND CENTRAL REGIONS. ALL THIS IN CONJUNCTION WITH BLOCKING PATTERN
DUE TO WEAK MID/UPPER LEVEL LOW OVER NWRN MEXICO. AT THE
SURFACE...COLD FRONTAL BOUNDARY WILL BE SLOWLY MOVING SWD THROUGH
THE SRN PENINSULA OF FL WITH SURFACE RIDGE ANCHORED OVER THE SOUTH
CENTRAL U.S. LOW PRESSURE OVER ALBERTA WILL MOVE SEWD DURING THE
PERIOD INTO S CENTRAL ONTARIO. COLD FRONT WILL ACCOMPANY THIS LOW
SEWD THROUGH CENTRAL MN AND ND INTO SRN MT.

..SRN FL PENINSULA...

SURFACE DEW POINTS ARE PROGGED TO BE IN THE UPPER 60S ACROSS THE
AREA AS THE FRONTAL BOUNDARY SLOWLY MOVES SWD. THIS WILL MAKE THE
AIR MASS POTENTIALLY UNSTABLE WITH MUCAPE BETWEEN 800 AND 1200 J/KG
TO SUPPORT A FEW STRONG THUNDERSTORMS. WHILE THERMAL LAPSE RATES
WILL BE WEAK...FCST SOUNDINGS DID INDICATE MID LEVEL DRYING WHICH
MAY BE ENOUGH FOR SOME ISOLATED WIND GUSTS WITH THIS ACTIVITY.

..SWRN AZ INTO THE RIO GRANDE VALLEY AND S TX...

MODELS INDICATE LOW LEVEL MOISTURE TRANSPORT ALONG FRONTAL BOUNDARY
WILL EXTEND SE-NW JUST SW OF THE RIO GRANDE SATURDAY. WITH WEAK
MID/UPPER LEVEL LOW OVER NWRN MEXICO AIDING THIS TRANSPORT...SIGNAL
IS THERE THAT WIDELY SCATTERED THUNDERSTORMS COULD DEVELOP
THROUGHOUT THIS REGION DURING THE DAY. PROGS SHOW THAT AIR MASS
WILL BE MARGINALLY UNSTABLE LIMITED BY CLOUD COVER WITH MUCAPE TO
500-700 J/KG AND LIFTED INDICES BETWEEN -2 AND -5 ACROSS THIS
REGION.

.MCCARTHY.. 04/27/2007

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