Sunday, September 16, 2007

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 160450
SWODY1
SPC AC 160448

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1148 PM CDT SAT SEP 15 2007

VALID 161200Z - 171200Z

..NO SVR TSTM AREAS FORECAST...

..SYNOPSIS...

LARGE SCALE PATTERN WILL BECOME SOMEWHAT MORE CONDUCIVE FOR
ORGANIZED DEEP CONVECTION EARLY THIS WEEK AS HEIGHTS LOWER ACROSS
THE NRN HALF OF THE U.S. AND MID-HIGH LEVEL FLOW INCREASES FROM
PORTIONS OF THE GREAT BASIN INTO THE UPPER GREAT LAKES REGION.
EARLY IN THIS TRANSITION PATTERN THE PRIMARY IMPEDIMENT FOR SEVERE
THUNDERSTORM DEVELOPMENT WILL BE THE NWD TRANSPORT OF
MOISTURE/INSTABILITY BENEATH THIS STRENGTHENING FLOW ALOFT.

..AZ TO CO...

HEIGHT FALLS INTO THE NRN GREAT BASIN SHOULD ENHANCE DEEPER SWLY
TRAJECTORIES FROM AZ INTO CO...ALLOWING MOIST PLUME AND HIGHER
PRECIPITABLE WATER...GREATER THAN ONE INCH...TO SPREAD ACROSS THE
4-CORNERS REGION INTO PORTIONS OF THE CNTRL ROCKIES. LATE EVENING
MODEL GUIDANCE SUGGESTS FLOW ALOFT WILL GRADUALLY INCREASE FROM NRN
AZ INTO CO AS UPPER TROUGH DIGS INTO NV LATE IN THE PERIOD. THIS
INCREASE IN FLOW SHOULD PROVIDE MORE THAN ENOUGH SHEAR FOR UPDRAFTS
TO ATTAIN AT LEAST MULTICELL CHARACTERISTICS BY LATE AFTERNOON AS
THUNDERSTORMS INTENSIFY WITHIN DEEPER MOIST PLUME. ISOLATED
DAMAGING WIND GUSTS OR PERHAPS SOME HAIL MAY ACCOMPANY THE STRONGER
STORMS.

..ELSEWHERE...

WEST COAST SEA BREEZE SHOULD BE ACTIVE ON SUNDAY ALONG THE FL
PENINSULA AS ELY COMPONENT INCREASES AND DEEPENS ALONG SRN FRINGE OF
LARGE SFC ANTICYCLONE. POOR LAPSE RATES SHOULD LIMIT SEVERE
THREAT...ALTHOUGH A WET MICROBURST CAN NOT BE RULED OUT.

A FEW THUNDERSTORMS WILL ALSO DEVELOP ACROSS THE NRN ROCKIES AS
TEMPERATURES WARM BENEATH MEAN LONG WAVE TROUGH. LIMITED
MOISTURE/INSTABILITY APPEAR INADEQUATE FOR ORGANIZED SEVERE STORMS.

INCREASING LLJ ACROSS THE CNTRL PLAINS WILL SOON ALLOW NWD TRANSPORT
OF GULF MOISTURE TO RETURN TO KS/NEB/SD. IT APPEARS THUNDERSTORM
POTENTIAL WILL INCREASE INTO THE DAY2 PERIOD ACROSS THIS REGION AS
SHORTWAVE TROUGH EJECTS ACROSS THE PLAINS. UNTIL THEN...LOW LEVEL
WARM ADVECTION SHOULD BE THE PRIMARY FORCING MECHANISM FOR
CONVECTIVE DEVELOPMENT...AND THAT SHOULD BE MAINLY AFTER 00Z.

.DARROW/CROSBIE.. 09/16/2007

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