SWODY2
SPC AC 191716
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1216 PM CDT WED SEP 19 2007
VALID 201200Z - 211200Z
..THERE IS A SLGT RISK OF SVR TSTMS PORTIONS ERN DAKOTAS AND MN...
..SYNOPSIS...
MID/UPPER LEVEL LARGE SCALE PATTERN WILL CONTINUE TO FEATURE WRN
MEAN TROUGH...AND RIDGING FROM NERN MEX AND S TX NEWD TOWARD
MID-ATLANTIC/NEW ENGLAND REGIONS. WRN TROUGH WILL BE ANCHORED BY
UPPER LOW NOW MOVING SWD ACROSS WRN ORE. THIS LOW IS EXPECTED TO
SETTLE SWD OVER COASTAL CENTRAL CA AND ADJACENT PACIFIC...BECOMING
QUASISTATIONARY AND ESSENTIALLY CUT OFF FROM NRN BELT OF WLYS BY END
OF PERIOD. NRN STREAM SHORTWAVE TROUGH -- NOW EVIDENT IN MOISTURE
CHANNEL IMAGERY WITHIN MEAN RIDGE POSITION OVER SERN AK -- IS FCST
TO DIG SEWD ACROSS WRN CANADA...REACHING SASK AND PERHAPS SWRN MB BY
21/12Z. ASSOCIATED SFC COLD FRONT WILL DEVELOP OVER CANADIAN
ROCKIES AND ADJACENT PRAIRIES AND MOVE ESEWD ACROSS MT...WY AND
DAKOTAS. BY END OF PERIOD...FRONT SHOULD REACH FROM FAR NWRN ONT
SWWD ACROSS MN...SERN SD...NRN/WRN NEB. WARM FRONT WILL LIFT NWD
ACROSS CENTRAL/NRN PLAINS. LEE TROUGHING SHOULD EXTEND GENERALLY
N-S ACROSS CENTRAL/SRN HIGH PLAINS FOR MUCH OF PERIOD...WITH
ASSOCIATED DRYLINE INTERSECTING COLD FRONT OVER W-CENTRAL OR SWRN
SD.
OTHERWISE...BROAD/WELL-DEFINED MID/UPPER LEVEL LOW -- NOW ANALYZED
OFFSHORE FMY -- SHOULD DRIFT WWD OR NWWD ACROSS ERN GULF. THIS
SYSTEM WILL CONTINUE TO CONTRIBUTE TO CONVECTIVE POTENTIAL OVER THAT
REGION...WITH SOME TROPICAL OR SUBTROPICAL CYCLONE DEVELOPMENT
POSSIBLE ACCORDING TO NHC OUTLOOKS. REF WMO HEADER ABNT20 KNHC FOR
MORE DETAILS.
..NRN PLAINS...UPPER MIDWEST...
MORNING MCS MAY MOVE NEWD ACROSS PORTIONS ERN DAKOTAS/WRN MN...WITH
LINGERING POTENTIAL FOR ISOLATED HAIL NEAR SVR LEVELS. THIS
ACTIVITY SHOULD DIMINISH THROUGH MID-DAY WITH LOSS OF LLJ-RELATED
ENHANCEMENTS TO ELEVATED BUOYANCY AND STORM-RELATIVE INFLOW.
CONDITIONAL POTENTIAL EXISTS FOR LATE AFTERNOON SVR...POSSIBLY
SUPERCELLULAR TSTM DEVELOPMENT. MOST FAVORABLE AREAS APPEAR TO BE
INVOF COLD FRONT BETWEEN DRYLINE AND WARM FRONT OVER CENTRAL/ERN
SD...AND PERHAPS ALONG/N OF ADJOINING SEGMENT OF WARM FRONT.
DAMAGING WINDS...LARGE HAIL AND CONDITIONAL TORNADO POTENTIAL EXISTS
FOR AFTERNOON/EARLY EVENING ACTIVITY INVOF WARM FRONT...WIND AND
HAIL ALONG COLD FRONT...AND HAIL BEING DOMINANT SVR MODE WELL N OF
WARM FRONT.
SRN PORTION OF CANADIAN SHORTWAVE TROUGH SHOULD EXTEND OVER NRN HIGH
PLAINS DURING LATTER HALF OF PERIOD...PRECEDED BY HEIGHT FALLS ALOFT
AND STG LOW LEVEL WAA REGIME ACROSS DAKOTAS. AMIDST THIS
PROCESS...PRIND WEAK TRIPLE-POINT LOW WILL FORM BY 21/00Z AT FRONTAL
INTERSECTION...INVOF CENTRAL OR WRN PORTIONS ND/SD BORDER. ALTHOUGH
OPERATIONAL NAM SEEMS TYPICALLY AGGRESSIVE WITH SFC MOISTURE RETURN
IN ADJACENT WARM SECTOR...UPSTREAM ANALYSES AND SREF CONSENSUS
GUIDANCE EACH SUGGEST LOW-MID 60S F DEW POINTS MAY EXTEND NWD ACROSS
CENTRAL PLAINS AND ERN SD/SWRN MN BY LATE AFTERNOON/EARLY EVENING.
ROBUSTNESS OF MOISTURE RETURN...SFC HEATING AND LIFT/CONVERGENCE
NEAR TRIPLE POINT WILL BE CRITICAL FOR DIURNAL INITIATION
POTENTIAL...BECAUSE STG CAPPING ALSO IS REASONABLY INDICATED IN
WRF/NAM-KF FCST SOUNDINGS. ANY ACTIVITY THAT CAN DEVELOP ALONG OR
JUST N OF WARM FRONT -- OR ALONG ANY FAVORABLY ALIGNED OUTFLOW
BOUNDARY LEFT BY MORNING ACTIVITY -- MAY BE SUPERCELLULAR WITH
TORNADO RISK. PRIND MLCAPES 1500-2000 J/KG ARE POSSIBLE DURING
PERIOD OF WARMEST LATE AFTERNOON BOUNDARY LAYER...ALONG WITH
FAVORABLE LOW-LEVEL AND DEEP-LAYER SHEAR. WITH 40-50 KT MIDLEVEL
WINDS AND RELATIVELY BACKED SFC FLOW...ENLARGED HODOGRAPHS IN FCST
SOUNDINGS YIELD POTENTIAL FOR 200-400 J/KG OF 0-3 KM SRH AROUND
21/00Z...AND EFFECTIVE SHEAR MAGNITUDE IN 45-50 KT RANGE.
MORE CONCENTRATED AREA OF SVR POTENTIAL -- INCLUDING SIGNIFICANT-SVR
HAIL OR TORNADOES WITH ANY DISCRETE SUPERCELLS -- MAY COMPEL UPGRADE
IN PROBABILITIES OVER PORTIONS ERN SD/WRN MN. ATTM...POTENTIAL
LIMITATIONS ON COVERAGE IMPOSED BY CAPPING...AND MESOSCALE BOUNDARY
UNCERTAINTIES...PRECLUDE LARGER UNCONDITIONAL PROBABILITIES ATTM
WITHIN CATEGORICAL SLGT RISK AREA.
.EDWARDS.. 09/19/2007
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@PO.UIUC.EDU with
"unsub wx-storm" in the body of your message. For more information write chris@lib.siu.edu.
No comments:
Post a Comment