Wednesday, May 16, 2007

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 161608
SWODY1
SPC AC 161606

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1106 AM CDT WED MAY 16 2007

VALID 161630Z - 171200Z

..THERE IS A SLGT RISK OF SVR TSTMS FROM PORTIONS OF NC/VA INTO SRN
NEW ENGLAND...

..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PART OF THE NRN MS RIVER
VALLEY INTO NRN IL...

..THERE IS A SLGT RISK OF SVR TSTMS OVER THE CENTRAL GULF COAST
REGION...

..SRN NEW ENGLAND ACROSS THE MID ATLANTIC...
CONSIDERABLE CLOUDS AND PRECIPITATION HAVE OVERSPREAD SURFACE COLD
FRONT NOW PUSHING EWD ACROSS CENTRAL NY/PA LATE THIS MORNING.
HOWEVER...MUCH OF THE URBAN CORRIDOR FROM VA INTO SRN NEW ENGLAND IS
NEARLY CLOUD FREE AND WILL SUPPORT STRONG HEATING/MARGINAL
INSTABILITY THIS AFTERNOON. SURFACE DEW POINTS ARE HOLDING IN THE
55-60F RANGE...DESPITE TEMPERATURES ALREADY NEAR 80F. FURTHER
HEATING WILL LIKELY BOOST MLCAPE INTO THE 500-1000 J/KG RANGE ACROSS
THIS REGION. ACTIVITY WILL LIKELY INTENSIFY NEAR THE
FRONT...POSSIBLY WITHIN ERN PART OF BROADER PRECIPITATION SHIELD
OVER ERN PA INTO NY EARLY THIS AFTERNOON. OTHER STORMS MAY INITIATE
ALONG LEADING EDGE OF CLOUDS AS CAP WEAKENS AND MLCAPE EXCEEDS 500
J/KG.

SHOULD SEE AN INCREASE IN SEVERE THREAT SPREADING FROM THE
POCONOS/CATSKILLS INTO THE CT RIVER VALLEY BY THE MID AFTERNOON
WHERE CONVERGENCE WILL BE STRONGEST INVOF WEAK SURFACE LOW CENTER
MOVING INTO SWRN NEW ENGLAND. STEEP LOW LEVEL LAPSE RATES AND VERY
STRONG SHEAR WILL ENHANCE THE POTENTIAL FOR DAMAGING WINDS WITH THIS
ACTIVITY. SUPERCELLS WILL BE MORE LIKELY OVER THIS REGION...ALONG
WITH ATTENDANT THREAT OF A TORNADO OR TWO...AS LOW LEVEL FLOW
REMAINS MORE SLY AND ENHANCES LOW LEVEL SHEAR AHEAD OF THE SURFACE
LOW. THIS SLY FLOW OFF THE ATLANTIC/LONG ISLAND SOUND MAY DIMINISH
SEVERE THREAT NEAR THE COASTS AND INTO ERN MA.

STRONG TO SEVERE THUNDERSTORMS ARE ALSO LIKELY DURING THE LATE
AFTERNOON AND EARLY EVENING SPREADING WEST TO EAST INTO THE MID
ATLANTIC AND VA. THIS ACTIVITY WILL LIKELY BECOME OUTFLOW DOMINATED
WITH STEEP SUB-CLOUD LAPSE RATES/STRONG HEATING COMBINING WITH
STRONG UNIDIRECTIONAL FLOW IN THE LOW-MID LEVELS. BROKEN SQUALL
LINE OR SMALL SCALE BOW ECHOES ARE EXPECTED TO INCREASE THE THREAT
OF DAMAGING WINDS/TREES DOWN OVER THIS REGION UNTIL STORMS MOVE OFF
THE COAST BY 03Z.

..PORTIONS OF SRN WI INTO NRN IL...
STRONG UPPER LOW WAS WELL DEFINED ON SATELLITE IMAGERY MOVING SSEWD
NEAR DLH THIS MORNING. AHEAD OF THIS SYSTEM...HEATING WILL BE
ABUNDANT AND SUPPORT STEEP LOW LEVEL LAPSE RATES. IN ADDITION...
VERY COLD MID LEVEL TEMPERATURES SHOULD OVERCOME MID 40S SURFACE
DEWPOINTS AND SUPPORT MARGINAL INSTABILITY BY THE MID TO LATE
AFTERNOON. RUC FORECAST SOUNDINGS INDICATE MLCAPE APPROACHING 500
J/KG BY 21Z. FOCUSED ASCENT AHEAD OF APPROACHING UPPER SYSTEM
SHOULD THEREFORE SUPPORT SCATTERED LOW-TOPPED THUNDERSTORMS DURING
THE LATE AFTERNOON/EARLY EVENING. EXPERIMENTAL...HIGH-RES WRF
SOLUTIONS ARE IN AGREEMENT AND FOCUS STRONGER CORES INTO THIS AREA
LATER TODAY. EFFECTIVE SHEAR AROUND 30-35 KT MAY ALSO SUSTAIN A FEW
SMALL...LOW-TOPPED SUPERCELLS. MARGINALLY SEVERE HAIL WILL BE
PRIMARY SEVERE THREAT...BUT 3KM-CAPE AOA 150 J/KG AND PRONOUNCED
VORTICITY INVOF MID LEVEL LOW MAY SUPPORT A BRIEF TORNADO OR TWO AS
WELL. SEVERE THREAT...THOUGH MARGINAL...APPEARS TO BE CONCENTRATED
ENOUGH TO WARRANT HIGHER SEVERE PROBABILITIES AND ATTENDANT SMALL
SLGT RISK.

..CENTRAL GULF COAST TO THE SRN APPALACHIANS/CAROLINAS...
STORMS WILL BECOME QUITE NUMEROUS INVOF POCKET OF MID LEVEL
MOISTURE/COOLING WHICH HAS SHIFTED AWAY FROM THE LOWER MS RIVER
VALLEY AND INTO THE CENTRAL GULF COAST REGION. OTHER STORMS SHOULD
BECOME MORE NUMEROUS AHEAD OF STRONG COLD FRONT CROSSING THE SRN
APPALACHIANS THROUGH THE EARLY EVENING. MODERATE TO STRONG
INSTABILITY AND MODEST DEEP LAYER SHEAR COULD SUPPORT MULTICELL
ORGANIZATION. HOWEVER...OVERALL SEVERE THREAT SHOULD BE WITH
SHORT-LIVED/PULSE-TYPE WITH ATTENDANT THREATS OF HAIL/WIND BRIEFLY
EXCEEDING SEVERE LEVELS. HOWEVER... COVERAGE/CONCENTRATION OF
REPORTS MAY BE LIKE YESTERDAY OVER THE LOWER MS RIVER VALLEY AND
WARRANTS HIGHER SEVERE PROBABILITIES AND SLGT RISK INVOF THE CENTRAL
GULF COAST.

..SRN HALF OF FL...
12Z SOUNDINGS AT MFL AND TBW INDICATE MID LEVEL TEMPERATURES REMAIN
RATHER COOL WITH H5 TEMPS FROM -9 TO -11C. LAPSE RATES ARE
MARGINAL...THOUGH STRONG WARMING OF VERY MOIST BOUNDARY LAYER SHOULD
ONCE AGAIN SUPPORT MODERATE MLCAPE THIS AFTERNOON. THOUGH ELY LOW
LEVEL WINDS WILL STILL PUSH EAST COAST SEA BREEZE WELL INLAND...FLOW
IS NOT AS STRONG AS THE PAST FEW DAYS AND WILL ALLOW INLAND AREAS TO
DESTABILIZE MORE THIS AFTERNOON. EXPECT SCATTERED PULSE-TYPE
THUNDERSTORMS WILL DEVELOP NEAR THE SEA BREEZES AND INVOF E-W
STALLED SURFACE FRONT ACROSS CENTRAL FL...AND MARGINAL/BRIEF-LIVED
SEVERE THUNDERSTORMS MAY OCCUR.

..FOUR CORNERS REGION INTO SRN CO/NWRN NM...
COLD MID LEVEL TEMPERATURES AROUND -12C WILL ALLOW MODERATE
INSTABILITY TO DEVELOP ACROSS THIS AREA TODAY WITH STRONG AFTERNOON
HEATING. DEEP LAYER WLY FLOW/SHEAR REMAINS WEAK... THOUGH SSELY
SURFACE FLOW OVER NWRN NM SHOULD INCREASE SHEAR A BIT AS STORMS
SPREAD ESEWD LATER TODAY OFF HIGHER TERRAIN. MARGINALLY SEVERE HAIL
APPEARS TO BE PRIMARY THREAT WITH THESE STORMS... THOUGH OVERALL
SEVERE THREAT REMAINS LOW ATTM.

.EVANS/GRAMS.. 05/16/2007

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