SWODY2
SPC AC 250509
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1209 AM CDT TUE MAR 25 2008
VALID 261200Z - 271200Z
..NO SVR TSTM AREAS FORECAST...
..SYNOPSIS...
MOISTURE CHANNEL IMAGERY INDICATES PERSISTENT CYCLONIC GYRE OVER
GULF OF AK...ALONG WITH SHORTWAVE TROUGH IN ITS SWRN SEMICIRCLE THAT
WILL COME ASHORE PACIFIC NW EARLY IN DAY-2 PERIOD. THIS TROUGH
SHOULD MOVE ESEWD TO NEB/SD BY 27/12Z...FOLLOWED BY SERIES OF
UPSTREAM/PERTURBATIONS LARGELY TRAVELING ALONG AND N OF 130-145 KT
250 MB JET CORE. ASSOCIATED STEEP MIDLEVEL LAPSE RATES IN COLD AIR
ALOFT -- BENEATH LEFT EXIT REGION OF CYCLONICALLY CURVED UPPER JET
MAX -- MAY SUPPORT ISOLATED TSTMS WITHIN BROAD SWATH OF NWRN CONUS.
AT SFC...LEE CYCLONE SHOULD DEVELOP BY 27/00Z OVER NERN CO/SWRN NEB
AREA...WITH WARM FRONT BECOMING MORE SHARPLY DEFINED ESEWD ACROSS
KS/MO.
..CENTRAL/SRN PLAINS...
CONDITIONAL POTENTIAL FOR SUPERCELLS IS EVIDENT OVER PORTIONS SRN
PLAINS E OF DEVELOPING DRYLINE...GIVEN LIKELY OVERLAP OF BROADLY
CURVED HODOGRAPHS AND FAVORABLE DEEP-LAYER SHEAR PROFILES WITH
INCREASING LOW LEVEL MOISTURE. ATTM...IT APPEARS THAT MLCINH IN
BASE OF ELEVATED MIXED LAYER WILL REMAIN TOO STRONG...WITH LOW LEVEL
LIFT TOO WEAK...TO SUPPORT CONVECTIVE INITIATION IN THIS
ENVIRONMENT...DESPITE SOME NEARLY UNCAPPED NAM FCST SOUNDINGS.
STRONGEST LOW LEVEL CONVERGENCE/ASCENT WILL BE INVOF SFC LOW OVER
CENTRAL HIGH PLAINS...AS WELL AS SRN PERIPHERY OF MIDLEVEL DPVA IN
ADVANCE OF SHORTWAVE TROUGH. HOWEVER...THIS AREA ALSO WILL BE
DISPLACED FROM SIGNIFICANT LOW LEVEL MOISTURE. LATEST OPERATIONAL
NAM-WRF MAY BE TOO AGGRESSIVE WITH BOUNDARY LAYER MOIST ADVECTION
ACROSS MUCH OF CENTRAL/SRN PLAINS...GIVEN ITS OWN HISTORY WITH
EARLY-STAGE RETURN FLOW EVENTS...AND GIVEN CURRENT STATE OF GULF AIR
MASS MODIFICATION WITH SUBSTANTIAL 925-850 MB OFFSHORE FLOW STILL
EVIDENT OVER MUCH OF GULF COAST.
THEREFORE...EXPECT MINIMAL DEEP CONVECTION BEFORE DARK...WITH
POSSIBLE EXCEPTION OF VERY HIGH BASED ACTIVITY INVOF SFC LOW. SOME
POTENTIAL EXISTS FOR THIS ACTIVITY TO PRODUCE STG SFC GUSTS GIVEN
DEEP/DRY SUBCLOUD LAYERS AND STRENGTH OF AMBIENT FLOW IN
CLOUD-BEARING LAYER. HOWEVER...SVR POTENTIAL APPEARS TOO ISOLATED
AND UNCERTAIN TO WARRANT UNCONDITIONAL PROBABILITIES ATTM.
CONVECTION MAY PERSIST THROUGH EVENING/OVERNIGHT HOURS AS ASSOCIATED
REGIME OF ELEVATED/LOW-LEVEL ASCENT SHIFTS EWD ACROSS CENTRAL PLAINS
INTO PROGRESSIVELY LESS MOISTURE-DEFICIENT ENVIRONMENT. TOWARD END
OF PERIOD...THIS ACTIVITY MAY MOVE FAR ENOUGH E ACROSS CENTRAL
PLAINS AND CORN BELT TO AFFECT WRN PORTION OF AREAS PREVIOUSLY
COVERED BY SEPARATE CONVECTIVE REGIME DISCUSSED BELOW.
..OZARKS TO LOWER MO/OH RIVER VALLEY REGIONS...
LLJ -- ALREADY EVIDENT ATTM FROM SWRN/S-CENTRAL TX ACROSS CENTRAL K
AND OZARKS -- WILL UNDERGO CHARACTERISTIC DIURNAL/NOCTURNAL
OSCILLATIONS RELATED TO BOUNDARY LAYER DECOUPLING THROUGH PERIOD.
DURING DAY-2...SUFFICIENT AIR MASS MODIFICATION SHOULD OCCUR OVER
WRN GULF FOR NARROW PLUME OF MOISTURE TO ADVECT NEWD ACROSS THIS
REGION. ACCOMPANYING MOISTENING AMIDST LOW LEVEL WAA WILL SUPPORT
INCREASING TSTM POTENTIAL THROUGH MID-LATE EVENING HOURS OVER
MO/IL...SPREADING/MOVING ENEWD OVERNIGHT. TIME SERIES OF FCST
SOUNDINGS REASONABLY SUGGESTS BUOYANCY -- AND LIKEWISE THUNDER
POTENTIAL -- SHOULD BECOME WEAKER AND MORE ELEVATED WITH EWD EXTENT
ACROSS THIS SWATH OVERNIGHT AS LEADING PORTION OF STRONGEST WAA AND
MOISTENING GRADUALLY BECOMES MORE DIFFUSE. ERN EDGE OF TSTM
POTENTIAL THEREFORE IS MORE ILL-DEFINED THAN ANY CATEGORICAL LINE
CAN INDICATE.
.EDWARDS.. 03/25/2008
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