SWODY3
SPC AC 200708
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0208 AM CDT FRI MAR 20 2009
VALID 221200Z - 231200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
MODEL GUIDANCE IS IN GENERALLY GOOD AGREEMENT IN THE EWD PROGRESSION
OF A POWERFUL MIDLEVEL LOW AND ACCOMPANYING 90+ KT JET STREAK
THROUGH THE GREAT BASIN INTO THE FOUR CORNERS REGION. AT THE
SURFACE...SEPARATE LOW CENTERS INITIALLY OVER THE NRN HIGH PLAINS
AND GREAT BASIN WILL CONSOLIDATE INTO A RAPIDLY DEEPENING LEE
CYCLONE OVER ERN CO SUNDAY NIGHT. PACIFIC COLD FRONT ATTENDANT TO
THE UPPER SYSTEM WILL PROGRESS EWD THROUGH THE NRN ROCKIES...GREAT
BASIN AND LOWER CO VALLEY WITH THIS FEATURE REACHING THE HIGH PLAINS
BY THE END OF THE FORECAST PERIOD.
MEANWHILE...A LEE TROUGH SITUATED OVER THE HIGH PLAINS WILL
GRADUALLY TRANSITION TO MORE OF A DRYLINE PRIOR TO BEING OVERTAKEN
BY PACIFIC COLD FRONT MONDAY MORNING. FARTHER E...A NW-SE ORIENTED
WARM FRONT WILL INTENSIFY SUNDAY OVER PORTIONS OF THE NRN AND CNTRL
PLAINS INTO THE MID MS VALLEY. THE MAJORITY OF TSTM ACTIVITY
THROUGH THE DAY THREE PERIOD IS EXPECTED TO REMAIN FOCUSED NEAR AND
TO THE N OF THIS BOUNDARY.
...GREAT PLAINS...
AS MENTIONED IN THE DAY TWO DISCUSSION...A SHORT WAVE TROUGH IS
EXPECTED TO PRECEDE PRIMARY UPPER SYSTEM WITH THIS FEATURE LIFTING
NEWD THROUGH THE NRN AND CNTRL PLAINS INTO THE UPPER MS VALLEY. A
BAND OF ELEVATED TSTMS APPEARS LIKELY IN ADVANCE OF THIS SHORT WAVE
TROUGH /TO THE N OF SURFACE WARM FRONT/ WHERE A SSWLY LLJ WILL FOCUS
ASCENT/DESTABILIZATION. SOME HAIL WILL BE POSSIBLE WITH THE
STRONGER STORMS.
IN THE WAKE OF THESE INITIAL TSTMS..STEEP MIDLEVEL LAPSE RATES AND
INCREASING BOUNDARY LAYER MOISTURE WILL RESULT IN A MODERATELY
UNSTABLE AIR MASS BY AFTERNOON FROM PORTIONS OF THE DAKOTAS SWD INTO
THE SRN HIGH PLAINS. FORECAST SOUNDINGS SUGGEST THAT CAPPING AT THE
BASE OF THE EML WILL LIKELY INHIBIT TSTM DEVELOPMENT THROUGH MUCH OF
THE DAY GIVEN THE ABSENCE OF ANY LARGE-SCALE FORCING MECHANISMS.
HOWEVER...DEEPENING DRYLINE CIRCULATIONS AND SUSTAINED CONVERGENCE
ALONG WARM FRONT MAY BE SUFFICIENT TO INITIATE ISOLATED STORMS BY
LATE AFTERNOON OR EARLY EVENING.
CURRENTLY...THE HIGHEST LIKELIHOOD OF SURFACE-BASED INITIATION
APPEARS TO BE NEAR THE WARM FRONT-DRYLINE TRIPLE POINT OVER THE
CNTRL HIGH PLAINS. SHOULD STORMS DEVELOP AND BECOME
SUSTAINED...VERTICAL SHEAR WILL BE SUFFICIENT FOR SUPERCELLS CAPABLE
OF HAIL AND HIGH WINDS. GIVEN THE UNCERTAINTY IN INITIATION AND
STORM COVERAGE...ONLY LOW SEVERE PROBABILITIES WILL BE INCLUDED IN
THIS FORECAST.
ADDITIONAL ELEVATED TSTMS WILL BE POSSIBLE SUNDAY NIGHT WITHIN
INCREASING LOW-LEVEL WAA REGIME OVER PARTS OF THE NRN/CNTRL PLAINS
INTO UPPER MS VALLEY. SIMILAR TO ABOVE...SOME HAIL WILL BE POSSIBLE
WITH THE STRONGER STORMS.
...WRN STATES...
INTENSE DYNAMIC FORCING FOR ASCENT ASSOCIATED WITH PRIMARY UPPER
SYSTEM WILL SUPPORT THE DEVELOPMENT OF SCATTERED TSTMS BOTH ALONG
AND IN THE WAKE OF PACIFIC FRONT. A FEW STRONGER STORMS WILL BE
POSSIBLE DUE TO THE STEEP LAPSE RATES AND STRENGTHENING WIND FIELDS.
HOWEVER...AIR MASS WILL REMAIN RATHER DRY WHICH WILL LIMIT THE
DEGREE OF CONVECTIVE INSTABILITY. NO ORGANIZED SEVERE WEATHER IS
EXPECTED.
..MEAD.. 03/20/2009
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
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