SWODY1
SPC AC 030557
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1257 AM CDT FRI AUG 03 2007
VALID 031200Z - 041200Z
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS ERN NY AND NRN NEW
ENGLAND...
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE NRN PLAINS/HIGH
PLAINS...
..SYNOPSIS...
MORE PROGRESSIVE AND FASTER MID LEVEL FLOW WILL REMAIN CONFINED TO
THE NRN U.S. THIS PERIOD WITH A PAIR OF SHORT WAVE TROUGHS EMBEDDED
IN THIS FLOW EXPECTED TO DRIVE ORGANIZED TSTM DEVELOPMENT. THE
LEADING IMPULSE...PIVOTING THROUGH THE BASE OF A DEEP CYCLONE
CENTERED NEAR SRN HUDSON BAY...WILL TRACK EAST ACROSS SRN ONTARIO
AND QUEBEC AND PRODUCE WEAK TO MODEST HEIGHT FALLS AND LARGE SCALE
ASCENT ACROSS MUCH OF THE NORTHEAST TODAY. THE COLD FRONT
ACCOMPANYING THE MID/UPPER LEVEL SYSTEM WILL MAKE SLOW EWD PROGRESS
ACROSS NEW YORK AND NRN NEW ENGLAND THROUGH TONIGHT...AND SETTLE
GRADUALLY ESEWD INTO SRN NEW ENGLAND BY EARLY SATURDAY.
OUT WEST...ANOTHER SHORT WAVE/PV ANOMALY OF INTEREST WAS CURRENTLY
DEPICTED IN SATELLITE IMAGERY AND OBJECTIVE ANALYSIS DATA ACROSS THE
NRN GREAT BASIN/SOUTHEAST ID. THIS IMPULSE IS FORECAST TO ACCELERATE
EWD ACROSS WY TODAY AND OVER THE DAKOTAS THROUGH TONIGHT. SURFACE
LEE CYCLOGENESIS IS ANTICIPATED FROM SERN MT INTO ERN WY AS THE
UPPER WAVE DEVELOPS EWD THIS AFTERNOON. THIS LOW IS FORECAST TO
CONSOLIDATE AND SLOWLY DEEPEN WHILE TRACKING EAST ALONG A WARM FRONT
ACROSS SD THROUGH SATURDAY MORNING.
ELSEWHERE...EXTENSIVE MARITIME TROPICAL AIR MASS AND SCATTERED
DIURNAL TSTMS WILL PERSIST BENEATH GENERALLY WEAK MID LEVEL FLOW AND
BROAD LARGE SCALE RIDGING FROM THE SRN ROCKIES...ACROSS THE
PLAINS...INTO THE MIDWEST AND SOUTH.
..ERN NY TO NRN NEW ENGLAND...
A WARM/MOIST AIR MASS IS ALREADY IN PLACE ACROSS THE NORTHEAST WITH
ONGOING ISOLATED CONVECTION OCCURRING WITHIN A WEAK/LEADING MID
LEVEL TROUGH OVER THE ST. LAWRENCE VALLEY/LAKE ONTARIO. AN OUTFLOW
BOUNDARY FROM EARLIER STORMS APPEARS TO BE WEAKENING ACROSS NRN ME
ATTM. TIMING OF THE STRONGER UPSTREAM SHORT WAVE TROUGH...NOW
CROSSING NRN GREAT LAKES...INDICATES THAT MORE FOCUSED ASCENT WITH
THIS IMPULSE WILL BE SPREADING INTO PARTS OF UPSTATE NY AND VT BY
LATE MORNING. TIMING OF THIS SYSTEM MAY TEND TO LIMIT GREATER
DESTABILIZATION ACROSS SOME OF THE AREA DUE TO CLOUDS/TSTMS.
HOWEVER...GIVEN VERY WARM/MOIST CONDITIONS ALREADY IN PLACE...AND
DYNAMIC FORCING/LIFT LEADING TO STEEPENING MID LEVEL LAPSE RATES
WITH THE UPPER WAVE...CONVECTION SHOULD INTENSIFY AND INCREASE IN
COVERAGE THROUGH THE AFTERNOON.
GIVEN POCKETS OF POTENTIALLY STRONG INSTABILITY /MLCAPE OF 1500-2000
J PER KG/ INDICATED BY LATEST GUIDANCE...UNIDIRECTIONAL BULK SHEAR
OF 20-30KT FORECAST TO INCREASE STEADILY THROUGH THE DAY...AND
SUPPORTIVE LARGE SCALE ASCENT...EXPECT ONE OR TWO BANDS OF STRONG TO
SEVERE STORMS WITH HAIL AND HIGH WINDS TO SWEEP ACROSS THE REGION
AHEAD OF THE FRONT. LATEST 4KM WRF-NMM DEPICTS THE MOST SUPPORTIVE
JUXTAPOSITION OF SHEAR...FORCING...AND INSTABILITY FOR SUPERCELLS TO
EVOLVE ACROSS MAINE FROM ABOUT 17Z THROUGH 23Z. SHEAR WILL WEAKEN TO
THE SOUTH AND WEST BUT A FEW INTENSE STORMS WITH SOME HAIL AND WIND
DAMAGE POTENTIAL WILL ALSO BE POSSIBLE AHEAD OF THE DEEPER FRONTAL
CIRCULATION SPREADING EAST THROUGH THE EVENING.
..ROCKIES TO NRN PLAINS...
MID/UPPER WAVE WILL SPREAD EAST ACROSS WY AND AID LARGE SCALE ASCENT
ACROSS INCREASINGLY UNSTABLE AIR MASS FROM THE ROCKIES EWD AND SEWD
ACROSS THE HIGH PLAINS. DESPITE RELATIVELY WARM MID LEVEL
TEMPERATURES...HIGH MOISTURE CONTENT AND OROGRAPHIC/DYNAMIC FORCING
SHOULD PROMOTE INCREASINGLY WIDESPREAD DEEP CONVECTION. LOW LEVEL
SELY FLOW TOPPED BY STRENGTHENING WLY MID LEVEL FLOW WILL RESULT IN
DIRECTIONAL SHEAR SUPPORTIVE OF SUPERCELLS...LIKELY EVOLVING AND
EMBEDDED WITHIN A LARGER AREA OF RAIN/CONVECTION. MORE DISCRETE
STORMS APPEAR POSSIBLE ALONG LEE/THERMAL TROUGH TRAILING FROM THE
SURFACE LOW WHERE CAP MAY REMAIN STRONGER. ACTIVITY IS EXPECTED TO
GROW UPSCALE AND ORGANIZE INVOF DEEPENING SURFACE LOW FROM ERN WY
ACROSS WRN SD THROUGH LATE IN THE DAY. DIRECTIONAL SHEAR AND
INSTABILITY NEAR THE LOW AND WARM FRONT MAY BE SUFFICIENT FOR A
TORNADO OR TWO IF DISCRETE CONVECTION CAN OCCUR NEAR THESE FEATURES.
OVERALL PATTERN APPEARS TO SUPPORT THE EVOLUTION INTO AN MCS
DEVELOPING EAST ALONG THE WARM FRONT ACROSS SD THROUGH THE NIGHT.
THE CHANCE FOR SCATTERED STRONG TO DAMAGING WINDS MAY EVOLVE FROM
THE HIGH PLAINS EWD ACROSS SD AS THE MCS DEVELOPS ACROSS THIS REGION
AND IS MAINTAINED BY STRONG MASS INFLOW AND DESTABILIZATION ON THE
NOSE OF 40-50KT LOW LEVEL JET.
.CARBIN/GRAMS.. 08/03/2007
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