SWODY1
SPC AC 250624
DAY 1 CONVECTIVE OUTLOOK CORR 1
NWS STORM PREDICTION CENTER NORMAN OK
0124 AM CDT SUN MAY 25 2008
VALID 251200Z - 261200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPPER MS VALLEY/WRN
GREAT LAKES REGION SWWD TO THE SRN PLAINS...
CORRECTED NDFD GRID POINTS
...SYNOPSIS...
MODELS REMAIN FAIRLY CONSISTENT FOR THE DAY 1 FORECAST PERIOD WITH
INDICATIONS OF MAINTAINING A COMPLEX LARGE-SCALE PATTERN /I.E. REX
BLOCK OVER WRN N AMERICA AND A DEEP VORTEX OVER NERN CANADA/. MID/
UPPER LOW...CURRENTLY RESIDING OVER THE NRN HIGH PLAINS...IS
FORECAST TO OPEN AND GRADUALLY DE-AMPLIFY AS IT MOVES EWD INTO
CONFLUENT FLOW REGIME ALONG SRN EXTENT OF ERN CANADA TROUGH. THIS
WILL EFFECTIVELY LOWER HEIGHTS ACROSS THE UPPER GREAT LAKES.
FINALLY...A SHORT WAVE TROUGH WILL ROUND BROADER...WRN U.S. CLOSED
LOW/TROUGH...WITH THIS FEATURE MOVING NEWD THROUGH THE LOWER CO
VALLEY INTO FOUR CORNERS REGION.
IN THE LOW LEVELS...PRIMARY FEATURE OF INTEREST WILL BE SURFACE LOW
ATTENDANT TO NRN PLAINS MID/UPPER LEVEL CIRCULATION WHICH WILL
DEVELOP EWD ALONG THE INTERNATIONAL BORDER FROM NWRN ND INTO NRN MN
BY 26/00Z...AND THEN INTO THE UPPER GREAT LAKES. A WARM FRONT WILL
PRECEED THIS LOW...LIFTING NEWD THROUGH THE UPPER MS VALLEY TODAY
AND EXTEND FROM THE UPPER GREAT LAKES TO LOWER OH VALLEY BY EARLY
THIS EVENING. A TRAILING PRE-FRONTAL TROUGH WILL PUSH EWD INTO THE
UPPER MS VALLEY BY SUNDAY AFTERNOON. THIS BOUNDARY SHOULD EXTEND
SWWD THROUGH WRN IA/ERN NEB TO DEVELOPING LOW PRESSURE OVER ERN CO.
A DRYLINE WILL EXTEND FROM INTERSECTION WITH PRE-FRONTAL TROUGH OVER
S-CNTRL NEB/N-CNTRL KS SWD TO ALONG TX PANHANDLE/WRN OK BORDER INTO
WRN TX.
...UPPER MS VALLEY/WRN GREAT LAKES TO CENTRAL PLAINS...
SWLY LOW LEVEL WINDS ARE EXPECTED TO PERSIST TODAY FROM THE CENTRAL
PLAINS INTO THE UPPER MS VALLEY/WRN GREAT LAKES REGION AS NRN PLAINS
UPPER TROUGH SHIFTS EWD. THIS WILL ALLOW MOISTURE TO CONTINUE TO
SURGE NEWD AS WARM FRONT LIFTS TOWARD THE UPPER GREAT LAKES.
SURFACE DEWPOINTS IN THE LOWER 60S SHOULD REACH PARTS OF NERN MN/WRN
UPPER MI...WITH UPPER 60S-AROUND 70 LIKELY INTO ERN IA/SWRN WI.
SURFACE HEATING IS EXPECTED TO COMMENCE LATER THIS MORNING IN THE
WAKE OF EARLY MORNING CONVECTION...AND AHEAD OF PRE-FRONTAL TROUGH.
THIS COMBINED WITH THE MOISTURE AND STEEP MID LEVEL LAPSE RATES WILL
SUPPORT A MODERATE-VERY UNSTABLE AIR MASS /MUCAPE RANGING FROM
2000-3500 J/KG/ FROM SERN MN/SWRN WI TO SERN NEB AND ERN KS.
RIGHT ENTRANCE REGION OF AN UPPER LEVEL JET WILL BE OVER THE UPPER
GREAT LAKES. THIS COMBINED WITH ASCENT ATTENDANT TO HEIGHT FALLS AS
NRN PLAINS LOW SHIFTS EWD AND SEVERAL MID LEVEL IMPULSES TRACK NEWD
WITHIN STRONG SWLY FLOW ALOFT WILL AID IN THE DEVELOPMENT OF TSTMS
THIS AFTERNOON FROM THE NRN MN SURFACE LOW SWWD ALONG THE TRAILING
PRE-FRONTAL TROUGH TO THE CENTRAL PLAINS. EFFECTIVE BULK SHEAR
AROUND 50 KT ACROSS THIS ENTIRE REGION SUGGESTS THREAT FOR TORNADIC
SUPERCELLS...SOME STRONG INTO THE UPPER MS VALLEY. THE STRONG
INSTABILITY AND STEEP LAPSE RATES WILL ENHANCE THE POTENTIAL FOR
HAIL...SOME VERY LARGE...AND DAMAGING WINDS.
MODELS SUGGEST A COUPLE OF MESOSCALE CONVECTIVE COMPLEXES WILL
DEVELOP THIS EVENING THROUGH TONIGHT. ONE WILL BE SERN NEB/NERN KS
INTO SRN IA/NRN MO...WITH THE SECOND...FORWARD PROPAGATING... ACROSS
SRN WI/NRN IL. THIS ACTIVITY WILL BE LOCATED ALONG A LLJ AXIS WITH
WARM AIR/MOISTURE ADVECTIONS COMBINED WITH STEEP LAPSE RATES
SUPPORTING BOTH A THREAT FOR HAIL AND DAMAGING WINDS INTO THE
OVERNIGHT PERIOD. SOME ACTIVITY MAY REACH AS FAR EAST AS LOWER MI.
...SRN PLAINS...
DRY LINE SHOULD MIX EWD ACROSS WRN KS AND THE TX PANHANDLE...WITH
MODELS INDICATING THE POTENTIAL FOR DIURNAL TSTM DEVELOPMENT SWD
ALONG THE EXTENT OF THIS BOUNDARY. STRONG SURFACE HEATING AND STEEP
LAPSE RATES WILL SUPPORT MODERATE INSTABILITY. DEEP LAYER SHEAR IS
EXPECTED TO DECREASE WITH SWD EXTENT...WHICH WOULD SUGGEST THAT THE
STRONGEST AND MORE ORGANIZED STORMS WILL BE ACROSS WRN KS INTO WRN
OK AND THE TX PANHANDLE.
...PARTS OF LOWER MS VALLEY INTO AL...
MODELS SUGGEST TSTMS WILL BE POSSIBLE ACROSS PARTS OF THIS REGION
TODAY WITHIN A VERY MOIST AND MODERATELY UNSTABLE AIR MASS. WEAK
DEEP LAYER SHEAR WILL TEND TO LIMIT THE POTENTIAL FOR ORGANIZED
STORMS...BUT LOCALLY STRONG WET MICRO-BURST WINDS SHOULD BE THE
GREATEST THREAT.
...PARTS OF PACIFIC NW...
A CONTINUATION OF COLD MID LEVEL TEMPERATURES WITHIN THE BROAD WRN
U.S. UPPER TROUGH WILL SUPPORT WEAK INSTABILITY AGAIN TODAY ACROSS
PARTS OF ORE/ID INTO NRN NV AND NRN CA. GENERALLY WEAK DEEP LAYER
SHEAR AND INSTABILITY WILL LIMIT THE SEVERE WEATHER THREAT...BUT THE
COLD MID LEVEL TEMPERATURES AND STEEP MID LEVEL LAPSE RATES MAY
RESULT IN A THREAT FOR ISOLATED HAIL AND/OR LOCALLY STRONG WIND
GUSTS.
..PETERS/GRAMS.. 05/25/2008
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