DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 131621
SWODY1
SPC AC 131619

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1119 AM CDT MON MAY 13 2013

VALID 131630Z - 141200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE NRN INTERMOUNTAIN WEST
INTO THE NRN HIGH PLAINS...

...NRN INTERMOUNTAIN WEST INTO THE NRN HIGH PLAINS...
WATER VAPOR IMAGERY SHOWS A STRONG UPPER SHORT WAVE TROUGH OFF THE
PACIFIC NW COAST PROGRESSING EWD IN ADVANCE OF AN UPSTREAM SYSTEM
APPROACHING 145W. MODEL GUIDANCE INDICATES THE LEAD SHORT WAVE
TROUGH WILL MOVE ONSHORE INTO WA/OREGON BY THIS EVENING AND CONTINUE
ENEWD TONIGHT TOWARD NRN MT AND SRN PARTS OF ALBERTA AND
SASKATCHEWAN. THIS WILL RESULT IN CONSIDERABLE FLATTENING OF THE
UPPER RIDGE CURRENTLY OVER THE NRN ROCKIES. A STRONG MID LEVEL JET
STREAK /80-90 KT AT 500 MB/ ACCOMPANYING THE TROUGH WILL TRANSLATE
EWD FROM THE PACIFIC NW INTO NRN MT PROVIDING STRONG VERTICAL SHEAR
OVER THE REGION.

A PACIFIC COLD FRONT IS FORECAST TO MOVE EWD IN ADVANCE OF THE SHORT
WAVE TROUGH...EXTENDING FROM NORTH CENTRAL MT INTO CNTRL ID AND SERN
OREGON BY 00Z...AND REACHING A CENTRAL ND/NRN WY/NW UT LINE BY THE
END OF THE PERIOD.

ALTHOUGH LOW LEVEL MOISTURE WILL BE MARGINAL WITH SURFACE DEW POINTS
GENERALLY IN THE 40S...LATEST SATELLITE PRECIPITABLE WATER VALUES
AROUND 0.75 INCH INDICATE SUFFICIENT MOISTURE IS PRESENT TO SUPPORT
CONVECTIVE DEVELOPMENT...GIVEN THE DYNAMIC FORCING FOR LARGE SCALE
ASCENT AHEAD OF THE TROUGH AND OROGRAPHIC LIFT IN FAVORED TERRAIN
LOCATIONS. STEEP MID LEVEL LAPSE RATES AND LOW LEVEL DIABATIC
HEATING FROM ERN OREGON ACROSS THE NRN ROCKIES AHEAD OF THE
ADVANCING COLD FRONT WILL RESULT IN A DEEP SURFACE-BASED MIXED LAYER
WITH CAPE REACHING 300-500 J/KG. CONSENSUS MODEL GUIDANCE INCLUDING
CONVECTION-ALLOWING MODELS INDICATE WIDELY SCATTERED HIGH-BASED
STORMS WILL DEVELOP ALONG A CORRIDOR FROM NERN OREGON INTO WRN MT
DURING THE 21-00Z PERIOD...WITH ACTIVITY SPREADING ENEWD INTO
TONIGHT. STRONG DEEP LAYER SHEAR WILL ENHANCE STORM ORGANIZATION
WITH POTENTIAL FOR A FEW BOWING SEGMENTS OR SUPERCELLS TO OCCUR WITH
STRONGER STORMS CAPABLE OF PRODUCING DAMAGING WIND GUSTS OR
MARGINALLY SEVERE HAIL. THE SEVERE THREAT MAY PERSIST INTO NORTH
CENTRAL/NERN MT FOR A FEW HOURS AFTER SUNSET BEFORE STORMS BEGIN
WEAKENING AS BOUNDARY LAYER COOLING/STABILIZATION OCCUR.

...SERN FL PENINSULA...
AS A COLD FRONT MOVES SWD FROM CENTRAL INTO SRN FL...CONVECTION IS
EXPECTED TO DEVELOP THIS AFTERNOON ESPECIALLY ALONG THE EAST COAST
SEA BREEZE NEAR THE I-95 CORRIDOR FROM NEAR PBI SWD TO MIA. 12Z
SOUNDINGS AT MFL AND KEY EXHIBIT MID LEVEL FLOW NEAR 30 KT
SUFFICIENT TO SUPPORT WEAKLY ORGANIZED CONVECTION...AND WITH DRY AIR
INDICATED ABOVE THE SURFACE LAYER THERE WILL BE POTENTIAL FOR
SEVERAL STORMS TO PRODUCE WET MICROBURSTS WITH STRONG WIND GUSTS.

...MID ATLANTIC REGION...
SATELLITE IMAGERY SHOWS A VIGOROUS SHORT WAVE TROUGH MOVING SEWD
ACROSS THE CENTRAL APPALACHIANS...WITH FOCUSED LARGE SCALE ASCENT
SPREADING ACROSS PARTS OF WV/VA/NRN NC THIS AFTERNOON. DESPITE VERY
LIMITED MOISTURE...STEEP LAPSE RATES ASSOCIATED WITH COLD MID LEVEL
TEMPERATURES ACCOMPANYING THE TROUGH WILL ENHANCE POTENTIAL FOR
LOW-TOPPED CONVECTION TO DEVELOP. FORECAST THERMODYNAMIC PROFILES
EXHIBIT SUFFICIENT CAPE WITHIN THE MIXED-PHASE HYDROMETEOR REGION TO
SUPPORT POTENTIAL FOR A FEW LIGHTNING FLASHES TO DEVELOP WITHIN
STRONGER UPDRAFTS.

..WEISS/COHEN.. 05/13/2013

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