SWODY1
SPC AC 251958
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0258 PM CDT SAT JUL 25 2009
VALID 252000Z - 261200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS WRN MID-ATLANTIC AND
CENTRAL APPALACHIANS TO S-CENTRAL PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS NRN ROCKIES...
--- UPDATES ---
...CENTRAL APPALACHIANS/UPPER OH VALLEY REGION...
OUTLOOK AREA SHIFTED EWD ACROSS WRN NY...PA...WV AND ADJOINING AREAS
OF VA/MD PER NEAR-TERM TRENDS DESCRIBED IN MESOSCALE DISCUSSION
1672...AS WELL AS POTENTIAL FOR DEVELOPMENT OVER MTNS OF ERN WV/WRN
VA TO PRODUCE SVR HAIL/GUSTS AS IT MOVES INTO WARMER AND MORE DEEPLY
MIXED SUB CLOUD LAYERS ACROSS ADJOINING PIEDMONT. REF WW 624 OVER
PA/NY PORTIONS OUTLOOK AREA. MEANWHILE MUCH OF OH HAS REMAINED
RELATIVELY STABLE WITH VEERED SFC WINDS BEHIND INITIAL/EARLY-MORNING
CONVECTIVE BAND. FARTHER SW...REF WW 623 AND SUBSEQUENT MESOSCALE
DISCUSSIONS FOR NEAR-TERM COVERAGE OF SVR THREAT FROM SRN INDIANA
ACROSS MUCH OF SRN/ERN KY.
...TN VALLEY REGION TO S-CENTRAL PLAINS...
EARLIER SVR THREATS STILL APPLY BUT ARE SHIFTED SWD/EWD SOMEWHAT
GIVEN CONVECTIVE TRENDS...AND STABILIZING EFFECTS OF CLOUDS/PRECIP
AND RESULTANT REDUCTION IN SVR THREAT WITH ANY TSTMS THAT FORM
BEHIND RAGGED SRN EDGE OF CLOUD SHIELD. DIFFERENTIAL HEATING ALONG
S EDGE OF CLOUD PLUME ALREADY HAS CONTRIBUTED TO POCKETS OF ENHANCED
CU/TCU DEVELOPMENT BETWEEN N-CENTRAL OK AND NWRN TN...AND
DEVELOPMENT OF WIDELY SCATTERED TSTMS IN CLUSTERS IS EXPECTED
THROUGH REMAINDER AFTERNOON. PERSISTENT AND INITIALLY ELEVATED
CONVECTIVE CLUSTER THAT HAS BEEN BACKBUILDING OVER CENTRAL KS ALSO
MAY EVOLVE TO SFC BASED TSTMS WITH POTENTIAL FOR ISOLATED STG-SVR
GUSTS AND HAIL.
...NRN ROCKIES...
CONVECTION IS DEVELOPING OVER ID BITTERROOTS AND ADJOINING PORTIONS
SWRN MT IN ENVIRONMENT OF FAVORABLE SHEAR...ASCENT AND SFC HEATING
AHEAD OF ERN WA MID/UPPER CYCLONE. OUTLOOK AREA APPEARS MRGL FOR
CATEGORICAL SLGT RISK GIVEN MRGL INSTABILITY. REF SPC MESOSCALE
DISCUSSION 1671 FOR NOWCAST TRENDS ACROSS THIS AREA.
..EDWARDS.. 07/25/2009
.PREV DISCUSSION... /ISSUED 1128 AM CDT SAT JUL 25 2009/
...SYNOPSIS...
MAIN SYNOPTIC FEATURE FOR STRONGER CONVECTION TODAY WILL BE
ASSOCIATED WITH AN UPPER LOW...CURRENTLY SITUATED OVER THE NRN GREAT
LAKES...AND FORECAST TO SHIFT ONLY SLOWLY EWD THROUGH THE PERIOD.
MORNING ANALYSIS SHOWS SHORTWAVE TROUGHS ROTATING AROUND THIS LOW
WERE MOVING EWD THROUGH THE OH VALLEY...WHILE ANOTHER IMPULSE WAS
PUSHING SEWD THROUGH KS/MO. SURFACE LOW PRESSURE WAS CENTERED IN THE
ERN U.P OF MI...WITH TRAILING COLD FRONT STRETCHING SWWD FROM THE
LOW INTO SRN KS/SERN CO. THE AREA ALONG AND AHEAD OF THE FRONT WAS
COVERED BY EXPANSIVE CLOUDS AND CONVECTION...WHICH COMPLICATES THE
FORECAST EVOLUTION FOR SEVERE WEATHER THIS AFTERNOON/EVENING.
...ERN OH VALLEY NEWD INTO WRN NY/PA...
COMBINATION OF OVERNIGHT CONVECTION AND CONTINUED MIGRATION OF
CLOUDS/PCPN THIS MORNING HAS SEEMINGLY REDUCED THE THREAT FOR SEVERE
STORMS ACROSS MUCH OF INDIANA AND NWRN OH. HOWEVER... MORNING
SUNSHINE AND LESS BOUNDARY LAYER STABILIZATION FROM EARLIER
CONVECTION INDICATES THAT STORMS...CURRENTLY LOCATED IN FAR SRN
IN/SRN OH ARE EXPECTED TO INTENSIFY AS THEY SHIFT/DEVELOP EWD LATER
THIS AFTERNOON INTO PORTIONS OF WRN NY/PA AND WV. ALTHOUGH
INSTABILITY WILL NOT BE PARTICULARLY STRONG...MLCAPES AROUND 1000
J/KG...FORCING ASSOCIATED WITH UPPER TROUGH COMBINED WITH
STRENGTHENING AND VEERING WIND PROFILES WILL SUPPORT SEVERE STORMS.
STORMS ARE MOST LIKELY TO ORGANIZE INTO LINE SEGMENTS AS WIND ALOFT
BECOME MORE UNIDIRECTIONAL FROM THE WEST. THIS SUGGESTS WIND DAMAGE
SHOULD BE THE PRIMARY THREAT...THOUGH THE FORECAST OF MOISTENING AND
VEERING WINDS IN THE BOUNDARY LAYER INDICATE A TORNADO OR TWO IS
ALSO POSSIBLE.
...NRN OK/SERN KS EWD INTO THE LOWER OH/TN VALLEYS...
WHERE STRONG HEATING CAN OCCUR...SOUTH OF FRONT AND CURRENT THICKER
CLOUDS...THE AIR MASS SHOULD BECOME MODERATELY TO STRONGLY UNSTABLE
WITH MLCAPES FROM 2000-2500 J/KG. PRESENCE OF SPEED MAX/IMPULSE
SWEEPING SEWD FROM KS/MO TOWARD THE KY/TN AREA WILL PROVIDE
SUFFICIENT SHEAR FROM NERN OK/SERN KS EWD INTO THE WRN TN/LOWER OH
VALLEYS FOR AN ARRAY OF STORMS...WITH SEVERAL ORGANIZED BANDS AND
CLUSTERS ANTICIPATED. DEGREE OF SHEAR AND INSTABILITY MAY ALSO
SUPPORT SUPERCELLS/BOW SEGMENTS WITH DAMAGING WINDS THE MAIN THREAT.
...SERN CO/NERN NM...
MODERATE INSTABILITY WILL DEVELOP LATER TODAY AS MOISTURE IS
ADVECTED WWD IN ELY FLOW BEHIND SWD MOVING COLD FRONT. FORCING ALOFT
WILL BE ABSENT...BUT COMBINATION OF UPSLOPE FLOW AND STRONG HEATING
NEAR HIGHER TERRAIN SUGGEST ISOLATED SEVERE STORMS MAY DEVELOP
DURING THE LATE AFTERNOON/EVENING HOURS.
...WRN MT...
UPPER LOW HAS RETREATED SLIGHTLY WWD FROM FRIDAY...WITH SHORTWAVE
RIDGING OCCURRING OVER CENTRAL MT. THIS IS RESULTING IN WEAK
DIFFLUENCE ALOFT ACROSS WRN MT. WITH HEATING...THE AIR MASS WILL
ONCE AGAIN BECOME WEAKLY UNSTABLE AND SUFFICIENT DEEP LAYER SHEAR
WILL EXIST FOR DIURNALLY-ENHANCED STORMS WITH AN ISOLATED HAIL/WIND
THREAT.
...ERN LOWER MI...
DESPITE WEAK SHEAR...STRONG FORCING AND MLCAPES AROUND 1000 J/KG MAY
YIELD A FEW MARGINALLY SEVERE STORMS AS THUNDERSTORM LINE MOVES EWD
ACROSS LOWER MI INTO THE MID AFTERNOON HOURS.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
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