Thursday, October 4, 2007

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 041257
SWODY1
SPC AC 041254

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0754 AM CDT THU OCT 04 2007

VALID 041300Z - 051200Z

..THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE MID MO AND
UPR MS VLYS...

..SYNOPSIS...
BROAD UPR TROUGH OVER THE NE PACIFIC EXPECTED TO CONTINUE AMPLIFYING
SE INTO THE FAR WRN U.S. THIS PERIOD AS SUBTROPICAL RIDGE EXPANDS
W/N ACROSS THE LWR GRT LKS/OH VLY. FARTHER S...SEPARATE SRN STREAM
JET WILL PERSIST FROM NRN BAJA CA NE INTO THE CNTRL/NRN PLNS.
SATELLITE LOOPS SHOW TWO IMPULSES IN THE SRN JET THAT LIKELY WILL
AFFECT TSTM DEVELOPMENT THIS PERIOD: ONE OVER SRN CA AND THE OTHER
OVER SRN CO.

AT LWR LVLS...SEASONABLY RICH BOUNDARY LYR MOISTURE WILL CONTINUE TO
SURGE N ACROSS THE ERN HALF OF THE PLNS AND THE MS VLY AS LLJ
STRENGTHENS DOWNSTREAM FROM AMPLIFYING TROUGH. A SFC LOW SHOULD
GRADUALLY CONSOLIDATE OVER THE CNTRL HI PLNS...S OF FRONTAL ZONE
THAT WILL BECOME STATIONARY OVER THE NRN PLNS/UPR MS VLY IN WAKE OF
NRN STREAM IMPULSE NOW CROSSING MANITOBA.

..MID MO INTO UPR MS VLY...
BOUNDARY LYR MOISTURE EXPECTED TO INCREASE MARKEDLY ACROSS ERN
NEB/IA/SE SD AND SRN MN LATER TODAY AND TONIGHT AS SLY LLJ
STRENGTHENS AND BROADENS S OF FRONTAL ZONE SETTLING S TOWARD REGION.
INCREASING MOISTURE...SFC HEATING AND CONVERGENCE IN EXIT REGION OF
LLJ SUGGEST THAT A CONDITIONAL THREAT FOR STRONG TO SVR STORMS WILL
EXIST ALONG AND S OF FRONT LATE THIS AFTN AND EARLY TONIGHT AS SRN
STREAM DISTURBANCE APPROACHES FROM CO. RELATIVELY WEAK /20-25 KT/
700 MB FLOW WILL LIMIT DEEP SHEAR...BUT SETUP COULD YIELD A FEW
SUSTAINED STORMS/POSSIBLE SUPERCELLS POSING A THREAT FOR SVR
WIND/HAIL AND AN ISOLATED TORNADO.

NOCTURNAL STRENGTHENING OF LLJ...AND DEVELOPMENT OF COUPLED JET
STRUCTURE ASSOCIATED WITH NRN STREAM IMPULSE CROSSING
ONTARIO...SUGGEST THAT AFTN/EVE STORMS IN ERN NEB AREA WILL
CONSOLIDATE INTO A CLUSTER THAT WILL PERSIST THROUGH EARLY FRIDAY.
THIS ACTIVITY COULD POSE A LIMITED THREAT FOR SVR WIND/HAIL AS IT
MOVES/DEVELOPS GENERALLY NE INTO PARTS OF SD/MN AND IA.

..CNTRL/SRN HI PLNS...
A LEE TROUGH WILL BECOME ESTABLISHED OVER THE CNTRL/SRN HI PLNS
TODAY AS SFC LOW EVOLVES ALONG THE CO/KS BORDER. LOW LVL MOISTURE
WILL CONTINUE TO INCREASE E OF THIS FEATURE...WITH DEWPOINTS IN THE
MID 60S POSSIBLE FROM NW TX/WRN OK INTO CNTRL PARTS OF KS AND NEB BY
LATE IN THE DAY. SEASONABLY WARM 700 MB TEMPERATURES WILL RESULT IN
CONSIDERABLE CINH. BUT FORCING FOR ASCENT ASSOCIATED WITH CO UPR
IMPULSE...AND CONVERGENCE ALONG LEE TROUGH...MAY SUPPORT ISOLATED TO
WIDELY SCATTERED STORMS ALONG AND E OF THE TROUGH LATE THIS AFTN
INTO EARLY TONIGHT. GIVEN UNSTABLE ENVIRONMENT /SBCAPE TO 1500 J
PER KG/ AND 25-30 KT DEEP SWLY SHEAR...A FEW OF THESE COULD PRODUCE
LOCALLY DAMAGING WIND AND POSSIBLY HAIL INTO EARLY TONIGHT.

..SWRN U.S...
SCTD DIURNALLY-ENHANCED TSTMS EXPECTED OVER MUCH OF AZ AND THE FOUR
CORNERS REGION THIS PERIOD...WHERE SFC AND PW DATA SUGGEST AMPLE
MOISTURE WILL BE PRESENT TO SUPPORT DEVELOPMENT. STORM LOCATION AND
COVERAGE WILL TO A LARGE EXTENT BE MODULATED BY UVV FIELD/DEEP
CONFLUENCE ZONES ASSOCIATED WITH EJECTING BAJA DISTURBANCE...
ALTHOUGH TERRAIN AND MOISTURE CONSIDERATIONS SUGGESTS THAT COVERAGE
WILL BE GREATEST INVOF THE MOGOLLON RIM.

WHILE MID LVL LAPSE RATES ARE NOT LIKELY TO BE VERY STEEP /AROUND 7
DEG C PER KM/...COMBINATION OF MODERATE SFC HEATING AND SEASONABLY
RICH MOISTURE SHOULD BOOST AFTN SBCAPE TO AOA 500 J/KG. COUPLED
WITH 30-40 UNIDIRECTIONAL LOW TO MID LVL SWLY FLOW AND 80+ KT HI-LVL
JET...SETUP COULD YIELD BANDS/CLUSTERS OF STORMS CONTAINING A FEW
SUSTAINED CELLS WITH DAMAGING WIND.

.CORFIDI/CROSBIE.. 10/04/2007

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