DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 272000
SWODY1
SPC AC 271958

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0258 PM CDT THU JUN 27 2013

VALID 272000Z - 281200Z

...THERE IS A MDT RISK OF SVR TSTMS ACROSS PORTIONS OF CENTRAL AND
EASTERN KANSAS...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CENTRAL
PLAINS/OZARKS VICINITY...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE E COAST STATES FROM
NY SWD TO GA/ERN AL/FL...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE SRN UPPER GREAT
LAKES AREA...

...DISCUSSION...
FEW CHANGES ARE BEING MADE THIS FORECAST WITH THE EXCEPTION OF
TWEAKS TO THE LINES BASED ON LATEST TRENDS. THE MAIN ADDITION HAS
BEEN TO ADD 5% TORNADO PROBABILITY TO THE SOUTHEAST PA/NERN MD/NJ/DE
AREA...CONSISTENT WITH EXISTING TORNADO WATCH 377.

OTHERWISE...STORMS CONTINUE TO EVOLVE AS ANTICIPATED...WITH NEW
DEVELOPMENT ONGOING INVOF THE CENTRAL U.S. MODERATE RISK AREA.
POTENTIAL FOR SUBSTANTIAL SEVERE WEATHER -- MAINLY IN THE FORM OF
VERY LARGE HAIL AND STRONG/DAMAGING WINDS -- REMAINS APPARENT THIS
AFTERNOON AND EVENING.

..GOSS.. 06/27/2013

.PREV DISCUSSION... /ISSUED 1123 AM CDT THU JUN 27 2013/

...SYNOPSIS...
FURTHER AMPLIFICATION OF THE UPPER FLOW PATTERN ACROSS THE EASTERN
PACIFIC INTO THE WESTERN U.S. IS FORECAST THROUGH THIS PERIOD.
UPPER RIDGING EXTENDING NORTH OF A BROAD SUBTROPICAL HIGH CENTERED
NEAR THE FOUR CORNERS REGION IS EXPECTED TO SHARPEN NORTHWARD ACROSS
THE NORTHERN U.S. ROCKIES INTO ALBERTA. AS THIS OCCURS...THE FIRST
COUPLE IN A SERIES OF MID/UPPER SPEED MAXIMUM...WITHIN A STRONG JET
NOSING INLAND OFF THE PACIFIC AROUND THE CREST OF THE UPPER
RIDGE...SHOULD CONTINUE TO DIG ACROSS THE NORTHERN PLAINS TOWARD THE
OHIO VALLEY.

AN UPPER TROUGH...WITH AN EMBEDDED LOW/MID-LEVEL CYCLONE... ALREADY
APPROACHING THE NORTHERN/CENTRAL APPALACHIANS...SHOULD PROGRESS
EASTWARD TOWARD NORTHERN MID ATLANTIC COASTAL AREAS LATER
TODAY...THEN NORTHEASTWARD TOWARD NEW ENGLAND TONIGHT...AS BROADER
SCALE UPPER TROUGHING BEGINS TO AMPLIFY ACROSS THE GREAT LAKES AND
OHIO VALLEY. MEANWHILE...A CONVECTIVELY GENERATED OR ENHANCED
PERTURBATION TRAILING THE LEAD IMPULSE APPEARS LIKELY TO MIGRATE
SOUTH SOUTHEASTWARD INTO/THROUGH EASTERN GULF COASTAL AREAS.

ASSOCIATED WITH THIS EVOLVING PATTERN...STEEPEST MID-LEVEL LAPSE
RATES...ASSOCIATED WITH VERY WARM AND STRONGLY CAPPING ELEVATED
MIXED LAYER AIR...WILL REMAIN CONFINED TO THE CENTRAL AND SOUTHERN
PLAINS...AND PROBABLY ERODED FROM NORTH TO SOUTH ACROSS THE CENTRAL
PLAINS...PERHAPS FROM THE SOUTH AND EAST ACROSS TEXAS.
HOWEVER...MID-LEVEL LAPSE RATES REMAIN MODESTLY STEEP ACROSS PARTS
OF THE UPPER MIDWEST...MUCH OF THE MISSISSIPPI VALLEY...AND THE
CENTRAL/EASTERN GULF STATES...NORTHEASTWARD TO THE LEE OF THE
CENTRAL AND SOUTHERN APPALACHIANS...WITH SOME STEEPENING POSSIBLE
WITH WEAK MID-LEVEL COOLING ACROSS THE LOWER GREAT LAKES TOWARD THE
HUDSON/CHAMPLAIN VALLEY TODAY. WITH SEASONABLY MOIST CONDITIONS
PREVAILING ACROSS MUCH OF THE MID MISSOURI VALLEY AND ADJACENT
CENTRAL PLAINS...AND MOST AREAS EAST OF THE MISSISSIPPI VALLEY...
DESTABILIZATION WITH DAYTIME HEATING SHOULD CONTRIBUTE TO
CONSIDERABLE THUNDERSTORM ACTIVITY TODAY...INCLUDING THE RISK FOR
SEVERE STORMS. OTHER SCATTERED THUNDERSTORM ACTIVITY APPEARS
POSSIBLE BENEATH THE WESTERN RIDGE...MAINLY ACROSS THE HIGHER
TERRAIN FROM THE SOUTHERN SIERRA NEVADA INTO THE CENTRAL ROCKIES.

...CENTRAL PLAINS INTO OZARK PLATEAU...
ISOLATED SEVERE STORM DEVELOPMENT IS ALREADY UNDERWAY ACROSS PARTS
OF THE MID MISSOURI VALLEY. THIS APPEARS IN RESPONSE TO FORCING
ASSOCIATED WITH A ZONE OF ENHANCED LOWER/MID TROPOSPHERIC WARM
ADVECTION ON THE NORTHEASTERN PERIPHERY OF THE SUBTROPICAL
HIGH...AND THE STRONGER CAPPING ELEVATED MIXED LAYER AIR ACROSS THE
CENTRAL AND SOUTHERN PLAINS. THIS IS EXPECTED TO PERSIST THROUGH
THE DAY...WITH UPSCALE CONVECTIVE GROWTH POSSIBLE INTO ONE OR TWO
SUBSTANTIVE SOUTHWARD PROPAGATING CONVECTIVE CLUSTERS...BENEATH
MODERATELY STRONG NORTHWESTERLY MID/UPPER FLOW. DEEP LAYER SHEAR
WILL BE MORE THAN SUFFICIENT FOR ORGANIZED STORM
DEVELOPMENT...INCLUDING SUPERCELLS. GIVEN THE THERMODYNAMIC
PROFILES...CHARACTERIZED BY STEEP MID-LEVEL LAPSE RATES...LARGE
CAPE...AND SIZABLE SUB-CLOUD TEMPERATURE-DEW POINT
SPREADS...STRONGEST STORMS WILL BE CAPABLE OF PRODUCING VERY LARGE
HAIL...PERHAPS WIND DRIVEN...ALONG WITH STRONG SURFACE COLD POOLS
CAPABLE OF PRODUCING SWATHS OF DAMAGING WIND GUSTS.

...ERN GULF STATES AND APPALACHIANS TO ATLANTIC SEABOARD...
DEEP LAYER SHEAR ACROSS MUCH OF THE REGION IS EXPECTED TO REMAIN
WEAK THROUGH THE PERIOD. HOWEVER...FORCING ASSOCIATED WITH THE MAIN
IMPULSE TURNING EAST OF THE NORTH CENTRAL APPALACHIANS...COUPLED
WITH AN ASSOCIATED BELT OF MODEST LOWER/MID-LEVEL FLOW...COULD
ENHANCE CONVECTIVE DEVELOPMENT LATE THIS AFTERNOON ACROSS PARTS OF
EASTERN VIRGINIA/MARYLAND AND THE DELMARVA PENINSULA INTO NORTHERN
MID ATLANTIC COASTAL AREAS. A LINE OR CLUSTER OF STORMS APPEARS
POSSIBLE...WITH THE RISK FOR POTENTIALLY DAMAGING WIND GUSTS.

OTHER SCATTERED STRONG/SEVERE STORM DEVELOPMENT STILL APPEARS
POSSIBLE IN THE PRESENCE OF MODERATE INSTABILITY...NORTHWARD INTO
UPSTATE NEW YORK...AND SOUTHWARD...TO THE SOUTH AND EAST OF THE
SOUTHERN APPALACHIANS. IT IS POSSIBLE THAT THE CONVECTIVELY
ENHANCED PERTURBATION COULD CONTRIBUTE TO ANOTHER CLUSTER OVER
STORMS TODAY ACROSS PARTS OF ALABAMA AND GEORGIA...WHICH COULD
PERHAPS DEVELOP SOUTHWARD INTO NORTHERN FLORIDA.

...UPPER MIDWEST INTO GREAT LAKES...
WEAK TO MODERATE INSTABILITY AND STRENGTHENING DEEP LAYER SHEAR
...TO THE CYCLONIC SIDE OF THE MID/UPPER JET STREAK NOSING SOUTHWARD
THROUGH THE UPPER MISSISSIPPI VALLEY...MAY CONTRIBUTE TO SCATTERED
STRONG/SEVERE STORM DEVELOPMENT TODAY INTO TONIGHT. THIS MAY
INCLUDE A COUPLE OF SUPERCELLS.

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