SWODY2
SPC AC 050555
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1255 AM CDT SUN AUG 05 2007
VALID 061200Z - 071200Z
..THERE IS A SLGT RISK OF SVR TSTMS PORTIONS CENTRAL/NRN PLAINS TO
UPPER MS VALLEY...
..THERE IS A SLGT RISK OF SVR TSTMS PORTIONS ERN MID-ATLANTIC AND
SRN NEW ENGLAND...
..SYNOPSIS...
MID/UPPER LEVEL PATTERN IN NRN STREAM IS FCST TO FLATTEN DOWNSTREAM
FROM TROUGHING ACROSS PACIFIC NW...WITH SWLY FLOW ALOFT ACROSS MUCH
OF CENTRAL/NRN ROCKIES AND NRN PLAINS REGION. STRONG SHORTWAVE
TROUGH -- NOW EVIDENT IN MOISTURE CHANNEL IMAGERY OVER SASK -- WILL
MOVE FROM HUDSON BAY REGION AND NERN/ERN ONT ACROSS QUE DAY-2. THIS
FEATURE MAY PHASE WITH INITIALLY SEPARATE PERTURBATION -- POSSIBLY
CONVECTIVELY INDUCED/ENHANCED -- ACROSS LOWER GREAT LAKES REGION.
MEANWHILE...PACIFIC NW TROUGH IS FCST TO SHIFT EWD OVER NRN ROCKIES.
AT SFC...COLD FRONT ASSOCIATED WITH CANADIAN SHORTWAVE TROUGH IS
EXPECTED TO MOVE EWD/SEWD ACROSS NEW ENGLAND/MID ATLANTIC REGION.
DECELERATING WRN SEGMENT OF THIS BOUNDARY WILL BLEND WITH
PRE-EXISTING/QUASISTATIONARY FRONTAL ZONE FROM SRN ONT WWD ACROSS
LOWER MI...LM...WI AND SRN MN...TO SFC CYCLONE OVER SRN SD/NRN NEB.
SFC TROUGHING WILL EXTEND SWWD FROM FRONTAL LOW ACROSS WRN NEB/NWRN
KS DURING AFTERNOON.
..NRN/CENTRAL PLAINS TO UPPER MS VALLEY...
MOST FOCUSED AREA FOR SVR POTENTIAL -- INCLUDING SUPERCELLS AND PSBL
BOWS -- APPEARS TO BE FROM AFTERNOON THROUGH EVENING...FROM VICINITY
SFC CYCLONE EWD 200-300 NM NEAR FRONT. SPECIFIC FRONTAL POSITION
MAY BE INFLUENCED BY PRIOR/DAY-1 MCS ACTIVITY...HOWEVER...PROGS ARE
IN INCREASINGLY CLOSE AGREEMENT ON GENERAL ZONE WITHIN WHICH
BOUNDARY SHOULD BE LOCATE FROM SRN SD EWD INVOF MN/IA BORDER. IN
THIS CORRIDOR...EXPECT BACKED SFC WINDS TO YIELD LARGE LOW LEVEL
HODOGRAPHS AND TO ENHANCE ALREADY FAVORABLE DEEP-LAYER SHEAR.
EXPECT STG HEATING OF BOUNDARY LAYER AIR MASS CONTAINING 70S F SFC
DEW POINTS...BENEATH 35-45 KT OF 500 MB WINDS AND 45-55 KT EFFECTIVE
SHEAR. WARM SECTOR MLCAPES 3000-5000 J/KG ARE
PROBABLE...OVERLAPPING WITH SRN PORTION OF 200-300 J/KG OF 0-3 KM
SRH INVOF FRONTAL ZONE.
CONVECTION SHOULD GROW IN COVERAGE AND MOVE EWD ACROSS OUTLOOK AREA
AFTER DARK...WITH SVR POTENTIAL PERHAPS EXTENDING TO NEAR MS RIVER
OVERNIGHT. FARTHER SW...WIDELY SCATTERED TSTMS ALSO MAY DEVELOP
ACROSS PORTIONS CENTRAL/SRN NEB AND NWRN KS...ATOP STRONGLY HEATED
BOUNDARY LAYER. THOUGH SHEAR WILL BE WEAKER THAN FARTHER N...SVR
HAIL AND GUSTS ARE POSSIBLE FROM LATE AFTERNOON INTO EARLY EVENING
BEFORE ACTIVITY WEAKENS.
..NERN CONUS...
SCATTERED TSTMS MAY BE ONGOING AROUND BEGINNING OF PERIOD OVER
PORTIONS NY/NEW ENGLAND...WITH AT LEAST MRGLLY FAVORABLE INFLOW
LAYER MOISTURE AND INSTABILITY ROOTED NEAR 30-35 KT LLJ. ACTIVITY
SHOULD OCCUR ABOVE LAYER OF NEAR-SFC RETURN FLOW THAT STILL IS
RATHER INCOMPLETELY MODIFIED AS OF 06/12Z...HOWEVER MOIST/WARM
ADVECTION WILL PERSIST THROUGH DAYLIGHT HOURS IN NARROW PLUME AHEAD
OF FRONTAL ZONE. IN COMBINATION WITH DIURNAL HEATING...BOUNDARY
LAYER THETAE SHOULD INCREASE ENOUGH OVER PORTIONS ERN NEW ENGLAND
AND MID-ATLANTIC REGIONS TO SUPPORT SFC-BASED CONVECTION. ACTIVITY
MAY PRODUCE DAMAGING DOWNDRAFTS AND MRGLLY SVR HAIL. ALTHOUGH LAPSE
RATES WILL BE RELATIVELY WEAK...EXPECT WEAK LARGE SCALE ASCENT NEAR
SRN PERIPHERY OF ERN CANADIAN TROUGH...PERHAPS ENHANCED ON MESOSCALE
IN CASE OF ANY MCV FROM PRIOR/UPSTREAM/DAY-1 ACTIVITY.
..NRN HIGH PLAINS...
THOUGH OPERATIONAL AND SREF PROGS ARE RATHER INCONSISTENT WITH
TIMING OF MID/UPPER TROUGH EJECTION...ASSOCIATED LARGE SCALE ASCENT
SHOULD SPREAD OVER PORTIONS MT DURING AFTERNOON THROUGH OVERNIGHT
HOURS. WEAK/RESIDUAL BOUNDARY LAYER MOISTURE AND DIABATIC HEATING
OF POST-FRONTAL AIR MASS MAY BE SUFFICIENT TO SUPPORT HIGH BASED
TSTMS DURING AFTERNOON/EARLY EVENING OVER CENTRAL/ERN MT AND PERHAPS
AS FAR SE AS WRN SD...SOME OF WHICH MAY PRODUCE STG GUSTS AND HAIL
AS THEY MOVE NEWD AMIDST FAVORABLE DEEP-LAYER SPEED SHEAR PROFILES.
..VA TIDEWATER TO CENTRAL APPALACHIANS AND OH VALLEY...
WIDELY SCATTERED TO SCATTERED TSTMS IN CLUSTERS MAY DEVELOP INVOF
SFC FRONTAL ZONE VIRTUALLY ANYWHERE ACROSS THIS REGION...WITH
MESOSCALE BOUNDARY INTERACTIONS AND PERHAPS PRIOR OUTFLOWS AS
ENHANCING FOCI. RICH LOW LEVEL MOISTURE SHOULD BE COMMON WITHIN AND
S OF FRONTAL ZONE...WITH SFC DEW POINTS MID 60S TO LOW 70S F BEING
COMMON. IN COMBINATION WITH STG DIURNAL HEATING...MLCAPES AROUND
2000 J/KG LIKEWISE SHOULD BE RATHER WIDESPREAD...SUPPORTING INTENSE
UPDRAFTS. WEAK LOW-MIDDLE LEVEL FLOW AND LACK OF STRONGER
DEEP-LAYER SHEAR ALSO ARE EXPECTED...AND MAY LIMIT ORGANIZED SVR
POTENTIAL.
.EDWARDS.. 08/05/2007
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
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