SWODY1
SPC AC 141957
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0257 PM CDT MON JUL 14 2008
VALID 142000Z - 151200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS CENTRAL PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS NRN MN...
...SYNOPSIS...
DOMINANT UPPER AIR FEATURE FOR REMAINDER PERIOD WILL BE MEAN TROUGH
OVER ERN CONUS. ALTHOUGH HEIGHT RISES ARE FCST TO COMMENCE AFTER
ABOUT 15/06Z FROM CENTRAL APPALACHIANS NEWD ACROSS UPPER GREAT
LAKES...BEHIND SHORTWAVE TROUGH NOW OVER LH AND NOW MOVING THROUGH
MEAN TROUGH POSITION. HEIGHT WEAKNESS WILL EXTEND SSWWD ACROSS
ATLANTIC E OF GA...THEN OVER SRN FL. RELATED SFC FRONTAL ZONE
INITIALLY EXTENDS FROM MAINE SWWD ACROSS ERN NC...SRN GA...S-CENTRAL
LA...CENTRAL TX THROUGH E-CENTRAL NM. BOUNDARY WILL CONTINUE MOVING
EWD AS COLD FRONT ACROSS REMAINDER ERN NEW ENGLAND AND OFFSHORE
MID-ATLANTIC WATERS...BUT WILL BECOME QUASISTATIONARY FROM NC SWWD
ACROSS MS DELTA REGION. WRN SEGMENT OF FRONT SHOULD BEGIN
RETREATING NWD ACROSS WRN/NWRN TX AND ERN NM...BECOMING INCREASINGLY
DIFFUSE AMIDST FRONTOLYTIC PROCESS. SE TX/SWRN LA PORTION OF
FRONTAL ZONE...AS WELL AS DEEP-LAYER AREA OF LOW HEIGHTS/PRESSURE
OVER FL...WILL SUPPORT SCATTERED MULTICELL AND PULSE TSTMS WITH A
FEW STG-DAMAGING GUSTS POSSIBLE IN MOST INTENSE CELLS.
MEANWHILE...ANOTHER COLD FRONT -- ASSOCIATED WITH NRN STREAM
SHORTWAVE TROUGH OVER MB -- WAS ANALYZED FROM SERN MB SWWD ACROSS
N-CENTRAL ND TO E-CENTRAL MT. THIS FRONT SHOULD CONTINUE ESEWD
TOWARD UPPER BOUNDARY WATERS REGION OF NRN MN OVERNIGHT...AND SSEWD
ACROSS MOST OF ND. PREFRONTAL TROUGH AND SFC CONFLUENCE LINE IS
ANALYZED FROM CENTRAL CO VICINITY COS NEWD ACROSS NERN CO AND
ADJACENT PORTIONS SWRN NEB...NEWD OVER ANW/VTN AREA...THEN BETWEEN
PIR-ABR. THIS BOUNDARY SHOULD REMAIN QUASISTATIONARY EXCEPT WHERE
LOCALLY SHIFTED/MODULATED BY CONVECTIVE OUTFLOW PROCESSES.
...CENTRAL PLAINS...
WIDELY SCATTERED TO SCATTERED TSTMS IN CLUSTERS ARE POSSIBLE LATE
AFTERNOON INTO EVENING...WITH DAMAGING WIND AND LARGE HAIL POSSIBLE.
AIR MASS CONTINUES TO DESTABILIZE INVOF SFC BOUNDARY FROM CENTRAL
CO NEWD ACROSS NEB TO SD...PARTICULARLY OVER HIGH PLAINS OF CO WHERE
LINE OF DEEP/GLACIATING TOWERS ALREADY IS EVIDENT IN VIS IMAGERY.
OUTLOOK EMPHASIZES AREA OF MORE ROBUST LOW LEVEL MOISTURE BUT
STRONGER CAPPING FARTHER NE INVOF BOUNDARY -- PRIMARILY OVER NEB
SEGMENT -- WHERE COMBINATION OF STG SFC HEATING AND MAINLY 60S F DEW
POINTS UNDERLIE ELEVATED MIXED LAYER AIR MASS.
RUC APPEARS TO BE OVERAGGRESSIVE WITH MIXING PROCESSES ACROSS THIS
REGION...GIVEN OBSERVED STEADY/INCREASING DEW POINTS AT MANY
STATIONS ATTRIBUTABLE TO COMBINATION OF EVAPOTRANSPIRATION AND LOW
LEVEL MOIST ADVECTION. RUC THEREFORE MAY BE UNDERPLAYING BUOYANCY
IN SHORT TERM ANALYSES/FCSTS. ACCORDINGLY MODIFIED MODEL SOUNDINGS
SUGGEST DEEP/WELL-MIXED BOUNDARY LAYER WILL REMAIN...AND WILL
SUPPORT STG-SVR GUSTS AND LARGE HAIL VIA SUBCLOUD EVAPORATIVE
COOLING -- BUT WITH HIGHER INFLOW MOISTURE AMOUNTS CONTRIBUTING TO
MLCAPES IN 1500-2500 J/KG RANGE. STG DEEP-LAYER DIRECTIONAL SHEAR
WITH HEIGHT -- BENEATH 25-30 KT NWLY AROUND 500 MB -- WILL
CONTRIBUTE TO EFFECTIVE SHEAR MAGNITUDES 35-45 KT...INDICATING BLEND
OF MULTICELLULAR/SUPERCELLULAR MODES IS POSSIBLE. MAIN UNCERTAINTY
ATTM INVOLVES CONVECTIVE COVERAGE AND TIMING OF INITIATION.
...NRN MN...
NW FLOW REGIME ACROSS THIS REGION...WITH GENERALLY INCREASING
MID/UPPER LEVEL FLOW REGIME WITH NWD EXTENT...WILL CONTRIBUTE TO
FAVORABLE DEEP LAYER SHEAR FOR TSTMS INVOF SFC FRONTAL ZONE. SFC DEW
POINTS GENERALLY 50S F WILL COMBINE WITH COOL MIDLEVEL TEMPS AND SFC
DIABATIC HEATING -- SOMEWHAT MUTED BY PRESENT CLOUD COVER -- TO
YIELD MLCAPES 1000-1500 J/KG. MODIFIED RUC SOUNDINGS SUGGEST CINH
ALREADY HAS BECOME VERY WEAK IN NARROW CORRIDOR AHEAD OF CLOUD
PLUME...ALTHOUGH LOW LEVEL FORCING APPEARS TO BE VERY WEAK. ANOTHER
AREA OF CONVECTIVE DEVELOPMENT MAY BE CLOSER TO SFC COLD FRONT LATE
THIS AFTERNOON AND THIS EVENING. TIMING/LOCATION OF CONVECTIVE
INITIATION IS IN QUESTION...HOWEVER ANY TSTMS THAT DEVELOP MAY
PRODUCE LARGE HAIL AND SVR GUSTS IN ENVIRONMENT OF FAVORABLE
DEEP-LAYER SHEAR.
..EDWARDS/KIS.. 07/14/2008
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@LISTSERV.ILLINOIS.EDU with
"unsub wx-storm" in the body of your message. For more information write cnovy@cox.net.
No comments:
Post a Comment