SWODY2
SPC AC 280501
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1201 AM CDT MON APR 28 2008
VALID 291200Z - 301200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
PROGRESSIVE PATTERN IS FCST ALOFT...BOTH ON SYNOPTIC AND SHORTER
WAVELENGTHS. MEAN TROUGHING NOW EXTENDING SWD FROM HUDSON BAY
SHOULD CONSOLIDATE INTO MID-UPPER LOW OVER ST LAWRENCE VALLEY AND
LOWER GREAT LAKES REGION BY END OF PERIOD...WITH BROAD AREA OF
CYCLONIC FLOW FROM UPPER GREAT LAKES ACROSS APPALACHIANS AND E
COAST. SHORTWAVE TROUGH -- NOW ANALYZED OVER UPPER MS VALLEY
REGION...WILL PIVOT SEWD/EWD DAY-1...THEN EJECT NEWD FROM
VA/CAROLINAS REGION TO NEW ENGLAND AND DEAMPLIFY DAY-2. ASSOCIATED
SFC CYCLOGENESIS IS POSSIBLE OFFSHORE MID-ATLANTIC REGION BY
29/12Z...WITH RESULTING LOW LIFTING NNEWD ACROSS CAPE COD AND MAINE
COASTAL REGIONS.
MEANWHILE...HEIGHT FALLS ALOFT ARE EXPECTED OVER MUCH OF NWRN CONUS
IN ADVANCE OF COMPLEX BUT PROGRESSIVE UPPER CYCLONE THAT NOW IS
EVIDENT IN MOISTURE CHANNEL IMAGERY FROM GULF OF AK SWD ALONG
140S...WELL OFFSHORE BC/WA/ORE. BY END OF PERIOD...NEARLY SYMMETRIC
NRN STREAM PATTERN IS FCST WITH UPPER LOWS OVER NRN ROCKIES AND AS
NOTED ABOVE...AND MERIDIONAL RIDGING OVER GREAT PLAINS STATES.
LEE-SIDE SFC CYCLOGENESIS IS FCST OVER ERN MT/WRN DAKOTAS...WITH
TROUGHING SSEWD ACROSS SRN HIGH PLAINS...BY 30/12Z.
...NRN ROCKIES AND NRN HIGH PLAINS...
ISOLATED TO WIDELY SCATTERED STMS ARE POSSIBLE OVER THIS REGION IN
SPORADIC/EPISODIC FASHION AS VERY COLD AIR ALOFT...E.G. 500 MB TEMPS
-28 TO -33 DEG C -- SHIFTS SLOWLY EWD OVER NRN ROCKIES. LOW LEVEL
THETAE WILL BE WEAK IN MOST AREAS...WITH ONLY MRGL MOISTURE TO
SUPPORT THUNDER. DIURNAL HEATING OF ERN PLATEAU AND HIGH PLAINS IN
MT ALSO MAY CONTRIBUTE TO STEEP AMBIENT LAPSE RATES...YIELDING
POTENTIAL FOR SOME VERY HIGH-BASED BUT STILL SFC-BASED CONVECTION
DURING LATE AFTERNOON...SOME OF WHICH MAY PRODUCE LTG GIVEN DEPTH OF
BUOYANT LAYER IN FCST SOUNDINGS. MLCAPES SHOULD REMAIN GENERALLY
AOB 200 J/KG. STG GUSTS AND SMALL HAIL MAY OCCUR IN MORE
INTENSE/PERSISTENT ACTIVITY...HOWEVER FCST MOISTURE AND INSTABILITY
APPEAR TOO WEAK TO WARRANT SVR PROBABILITIES.
...SRN/ERN NEW ENGLAND...
MRGL THUNDER POTENTIAL IS FCST...LIFTING NEWD ACROSS REGION DURING
DAYLIGHT HOURS. FIELD OF MIDLEVEL DPVA AND STG LOW LEVEL WAA WILL
SHIFT NEWD ACROSS AREA...IN ADVANCE OF EJECTING MID/UPPER SHORTWAVE
TROUGH. MOISTURE TRANSPORT -- ASSOCIATED WITH WAA CONVEYOR ABOVE
COOL/STABLE MARINE LAYER -- SHOULD BE SUFFICIENT TO RENDER NEARLY
SATURATED SOUNDINGS IN LOW LEVELS. EXPECT WEAK ELEVATED
BUOYANCY...E.G. MUCAPES UP TO 500 J/KG BASED ON NAM-KF SOUNDINGS.
..EDWARDS.. 04/28/2008
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