SWODY1
SPC AC 121252
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0752 AM CDT MON APR 12 2010
VALID 121300Z - 131200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE NORTHERN PLAINS...
...SYNOPSIS...
WATER VAPOR IMAGERY/UPPER AIR DIAGNOSTICS REFLECT A BROAD UPPER
TROUGH ADVANCING INLAND OVER ORE/NORTHERN CA THIS MORNING...WITH
THIS TROUGH EXPECTED TO ADVANCE EAST-NORTHEASTWARD OVER THE
INTERMOUNTAIN WEST THROUGH TONIGHT. IN RESPONSE...SURFACE
CYCLOGENESIS IS ANTICIPATED ACROSS PORTIONS OF WY...WITH A
CONSOLIDATING WARM FRONTAL ZONE FROM THE NORTHERN HIGH PLAINS TO THE
UPPER MS RIVER VALLEY. AN AMPLIFYING UPPER RIDGE AND SURFACE HIGH
PRESSURE WILL OTHERWISE PREVAIL EAST OF THE ROCKIES.
...NORTHERN PLAINS...
SCATTERED SHOWERS/TSTMS ARE ONGOING EARLY THIS MORNING FROM EASTERN
ND TO SOUTHERN MN/NORTHERN IA ON THE EDGE OF A STRENGTHENING
ELEVATED MIXED LAYER. WITH 1800 J/KG OF SOURCE REGION MUCAPE NOTED
PER THE 12Z OMAHA OBSERVED RAOB...A MARGINAL HAIL THREAT CANNOT BE
RULED OUT YET THIS MORNING MAINLY ACROSS NORTHERN IA/SOUTHERN
MN...BUT IN GENERAL THIS ACTIVITY SHOULD TEND TO REMAIN
ISOLATED/BELOW SEVERE LIMITS.
OTHERWISE...AN AMPLIFYING UPPER RIDGE AND ASSOCIATED HEIGHT RISES
WILL OCCUR OVER THE NORTHERN PLAINS/UPPER MIDWEST...AND A NORTHEAST
EXPANDING ELEVATED MIXED LAYER IS EXPECTED TO LARGELY CAP SURFACE
BASED TSTM DEVELOPMENT THROUGH THE AFTERNOON ACROSS THE MAJORITY OF
THE PLAINS.
AHEAD OF THE WESTERN STATES UPPER TROUGH...THE ARRIVAL OF LARGE
SCALE HEIGHT FALLS/EXIT REGION OF POLAR JET SHOULD CONTRIBUTE TO AN
INCREASE IN TSTMS ACROSS THE NORTHERN HIGH PLAINS PERHAPS LATE THIS
AFTERNOON...BUT MORE LIKELY THIS EVENING...INCLUDING PORTIONS OF WY
INTO EASTERN MT. ADDITIONAL TSTMS ARE EXPECTED TO DEVELOP AND
INCREASE IN COVERAGE/VIGOR LATE THIS EVENING/OVERNIGHT ACROSS
ND/ADJACENT SD INTO MN...WITHIN A 50+ LOW LEVEL JET AIDED ELEVATED
MOISTURE TRANSPORT REGIME TO THE NORTH OF A WNW-ESE ORIENTED WARM
FRONT. A STEEP LAPSE RATE ENVIRONMENT/AMPLE ELEVATED INSTABILITY AND
SUFFICIENT SHEAR THROUGH THE CLOUD BEARING LAYER WILL SUPPORT SOME
ELEVATED SUPERCELLS CAPABLE OF SEVERE HAIL TONIGHT.
...SOUTHERN HIGH PLAINS...
A FEW STRONG STORMS CANNOT BE RULED OUT THIS AFTERNOON/EARLY EVENING
WITHIN A WEAKLY CAPPED/MODESTLY MOIST BOUNDARY LAYER ACROSS MUCH OF
WEST TX AND/OR EASTERN NM. HOWEVER...GIVEN WEAK MID/UPPER FLOW AND
SUB-1000 J/KG MLCAPE IN MOST LOCALES...ORGANIZED/SUSTAINED STORMS
ARE UNLIKELY...WITH HAIL EXPECTED TO REMAIN BELOW 1 INCH CRITERIA.
..GUYER/GRAMS/JIRAK.. 04/12/2010
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