SWODY2
SPC AC 260540
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1240 AM CDT SAT JUL 26 2008
VALID 271200Z - 281200Z
...THERE IS A SLGT RISK OF SVR TSTMS SUN ACROSS PARTS OF THE MID
MISSOURI/MID MS VALLEYS INTO THE LWR OH VALLEY....
...THERE IS A SLGT RISK OF SVR TSTMS SUN ACROSS PARTS OF THE NRN
PLAINS....
...THERE IS A SLGT RISK OF SVR TSTMS SUN ACROSS PARTS OF THE NRN
MIDDLE ATLANTIC COAST STATES INTO SRN NEW ENGLAND....
...SYNOPSIS...
MODELS INDICATE THAT THE SOUTH CENTRAL PLAINS UPPER HIGH CENTER MAY
BEGIN TO WEAKEN DURING THIS FORECAST PERIOD...WHILE A CLOSED LOW IN
THE SOUTHERN BRANCH OF SPLIT POLAR WESTERLIES BEGINS TO SHIFT EAST
OF JAMES BAY. BUT...WITH ANOTHER CLOSED LOW LINGERING NEAR THE GULF
OF ALASKA SUNDAY...LITTLE CHANGE IN THE GENERAL LARGE-SCALE UPPER
PATTERN ACROSS THE U.S. IS PROGGED.
FLOW WILL REMAIN BROADLY CYCLONIC ACROSS THE PACIFIC NORTHWEST COAST
INTO THE NORTHERN ROCKIES...BEFORE TRANSITIONING TO ANTICYCLONIC
ACROSS THE NORTHERN PLAINS THROUGH THE UPPER MISSISSIPPI
VALLEY...THEN CYCLONIC ONCE AGAIN ACROSS THE GREAT LAKES/OHIO VALLEY
THROUGH THE NORTHEAST. WITHIN THIS REGIME...A SIGNIFICANT SHORT
WAVE IMPULSE IS PROGGED TO GRADUALLY PROGRESS ACROSS AND EAST OF THE
CANADIAN/NORTHERN U.S. ROCKIES...WHILE ANOTHER DIGS SOUTHEAST OF THE
LOWER GREAT LAKES REGION. PERHAPS ATTENDANT TO...OR JUST TRAILING
TO THE SOUTHWEST OF THE LATTER FEATURE...MODELS HAVE BEEN CONSISTENT
IN SUGGESTING THAT ANOTHER FAIRLY SIGNIFICANT CONVECTIVELY
GENERATED/ENHANCED IMPULSE WILL DIG SOUTHEAST OF THE MID MISSOURI
VALLEY THROUGH PARTS OF THE LOWER OHIO VALLEY BY 12Z MONDAY.
...MID MISSOURI VALLEY INTO THE LOWER OHIO VALLEY...
WHILE THE IMPULSE NEAR THE MID MISSOURI VALLEY AT THE OUTSET OF THE
FORECAST PERIOD IS FORECAST TO DIG SOUTHEAST OF THE STRONGER
WESTERLIES DURING THE DAY...AN ASSOCIATED MID-LEVEL SPEED MAXIMUM IS
EXPECTED TO ENHANCE SHEAR PROFILES AS IT NOSES TOWARD THE LOWER OHIO
VALLEY SUNDAY/SUNDAY NIGHT. COUPLED WITH MOISTENING AND
DESTABILIZATION...IN A FAVORABLE LOWER/MID TROPOSPHERIC WARM
ADVECTION REGIME ON THE EASTERN PERIPHERY OF AN ELEVATED MIXED LAYER
EMANATING FROM THE GREAT BASIN...THIS SHOULD CONTRIBUTE TO A
FAVORABLE ENVIRONMENT FOR SUPERCELLS AND ORGANIZED STORM CLUSTERS.
A MESOSCALE CONVECTIVE SYSTEM...OR REMNANTS OF ONE...STILL APPEARS
LIKELY TO RE-INTENSIFY OR REDEVELOP DURING THE DAYTIME HOURS ACROSS
PARTS OF THE MIDDLE MISSISSIPPI VALLEY. ACTIVITY WILL BE CAPABLE OF
PRODUCING DAMAGING WIND GUSTS AND LARGE HAIL AS IT SPREADS
SOUTHEASTWARD TOWARD THE LOWER OHIO VALLEY. AND...ITS POSSIBLE THAT
LOW-LEVEL WARM ADVECTION IN ITS WAKE COULD CONTRIBUTE TO ADDITIONAL
STRONG/SEVERE STORM DEVELOPMENT ACROSS THE MIDDLE MISSISSIPPI VALLEY
LATER IN THE AFTERNOON/EVENING HOURS...BEFORE WEAKENING/DIMINISHING
WITH BOUNDARY LAYER STABILIZATION OVERNIGHT.
...NORTHERN HIGH PLAINS...
IN THE WAKE OF THE SYSTEM DIGGING SOUTHEAST OF THE MIDDLE MISSOURI
VALLEY...AND AHEAD OF THE NEXT SYSTEM SHIFTING ACROSS THE ROCKIES
...MODERATE TO STRONG DESTABILIZATION IS EXPECTED BY SUNDAY
AFTERNOON...WITH MIXED LAYER CAPE ON THE ORDER OF 2000-3000 J/KG.
IN THE PRESENCE OF STRONG DEEP LAYER...ASSOCIATED WITH LIGHT
EASTERLY LOW-LEVEL WINDS BENEATH 30-40+ KT WESTERLY 500 MB FLOW...
THE ENVIRONMENT WILL BE FAVORABLE FOR SUPERCELL DEVELOPMENT OFF THE
HIGHER TERRAIN AND ACROSS EASTERN MONTANA. AND...MODELS ARE
SUGGESTIVE THAT LARGE-SCALE FORCING WILL BECOME SUFFICIENT TO AID
CONSOLIDATION OF ACTIVITY INTO AN ORGANIZED STORM CLUSTER CAPABLE OF
PRODUCING STRONG DAMAGING WINDS INTO THE WESTERN DAKOTAS... BEFORE
DIMINISHING SUNDAY NIGHT.
...NORTHERN MID ATLANTIC COAST STATES INTO NEW ENGLAND...
DEEP LAYER SHEAR IS EXPECTED TO REMAIN RELATIVELY MODEST NEAR THE
LEE SURFACE TROUGH. BUT...MODELS INDICATE THAT THE BOUNDARY LAYER
COULD BECOME RATHER UNSTABLE WITH STRONG HEATING SUNDAY. CAPE MAY
APPROACH OR EXCEED 2000 J/KG TO THE LEE OF THE CENTRAL
APPALACHIANS...PERHAPS AS FAR NORTH AS SOUTHERN NEW ENGLAND.
COUPLED WITH STEEP LOW-LEVEL LAPSE RATES...THE ENVIRONMENT SHOULD BE
FAVORABLE FOR POTENTIALLY DAMAGING WIND GUSTS AND SOME HAIL. STORM
DEVELOPMENT IS EXPECTED TO BECOME ENHANCED DURING THE PEAK AFTERNOON
HEATING HOURS BY MID/UPPER FORCING AHEAD OF THE SHORT WAVE TROUGH
DIGGING TO THE SOUTHEAST OF THE LOWER GREAT LAKES REGION.
..KERR.. 07/26/2008
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