SWODY1
SPC AC 221959
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0259 PM CDT SUN MAR 22 2009
VALID 222000Z - 231200Z
...NO SVR TSTM AREAS FORECAST...
...DAKOTAS AND NEBRASKA...
WATER VAPOR IMAGERY SHOWS A SOUTHWEST FLOW PATTERN IN PLACE ACROSS
THE SRN ROCKIES AND HIGH PLAINS WITH A DRY SLOT ADVANCING EWD ACROSS
THE CNTRL HIGH PLAINS WHERE A LEAD SHORTWAVE TROUGH IS LOCATED ATTM.
THIS FEATURE WILL MOVE EWD ACROSS CNTRL SD AND CNTRL NEB LATE THIS
AFTERNOON WITH THE THUNDERSTORMS ONGOING IN ERN SD GRADUALLY
BECOMING MORE VIGOROUS EXPANDING SWD INTO ERN NEB BY EARLY EVENING.
ALTHOUGH NOT MUCH INSTABILITY IS PRESENT ACROSS THE CNTRL PLAINS
ATTM...THE RUC AND OTHER SHORT-TERM MODELS RAPIDLY DEVELOP AN AXIS
OF INSTABILITY FROM CNTRL KS NWD INTO SE SD AS THE LOW-LEVEL JET
CRANKS UP THROUGH EARLY EVENING. IN RESPONSE...THE RUC DEVELOPS A
CLUSTER OF ELEVATED STORMS IN NE NEB AND SE SD BY 03Z. IN
ADDITION...THE NELIGH NEB SHOW 0-6 KM SHEAR OF 35 TO 40 KT. THIS
ENVIRONMENT SHOULD SUPPORT A HAIL THREAT. HOWEVER...FORECAST
SOUNDINGS WEAKEN VERTICAL SHEAR PROFILES WITH TIME THROUGH EARLY
EVENING. ALSO...A THERMAL RIDGE ALOFT IS PRESENT IN THE CNTRL
PLAINS. THESE TWO FACTORS COULD KEEP ANY THREAT MARGINAL THROUGH
EARLY EVENING.
DURING THE OVERNIGHT PERIOD...AN IMPRESSIVE UPPER-LEVEL TROUGH IS
FORECAST TO MOVE INTO THE SRN ROCKIES. THE EXIT REGION OF A 80 TO
100 KT MID-LEVEL JET ASSOCIATED WITH THE TROUGH WILL OVERSPREAD WRN
NEB AND WRN SD. SEVERAL MODELS DEVELOP ISOLATED THUNDERSTORMS IN
THIS AREA AROUND MIDNIGHT WHERE MODERATE VERTICAL SHEAR WILL BE IN
PLACE ALONG WITH MUCAPE VALUES IN THE 500 TO 1000 J/KG. IF STORMS
CAN DEVELOP IN THIS ENVIRONMENT...A HAIL THREAT SHOULD EXIST.
HOWEVER...UNCERTAINTY STILL EXISTS CONCERNING CONVECTIVE INITIATION.
IF STORMS CAN INITIATE THEN THE THREAT COULD CONTINUE THROUGH LATE
IN THE PERIOD.
...KANSAS/NW OKLAHOMA...
LATEST WATER VAPOR IMAGERY SHOWS A SUBTROPICAL PLUME OF MID-LEVEL
MOISTURE EXTENDING NEWD ACROSS WEST TX INTO OK AND KS. BENEATH THE
PLUME...THE RUC ANALYZES A 30 TO 40 KT JET OVER SCNTRL KS. THIS
FEATURE SHOULD STRENGTHEN THIS EVENING WITH ELEVATED INSTABILITY
INCREASING ALONG AN AXIS FROM NW OK EXTENDING NWD ACROSS WCNTRL KS.
ISOLATED THUNDERSTORMS MAY DEVELOP ALONG THIS AXIS OF INSTABILITY
EARLY THIS EVENING DUE TO WARM ADVECTION ASSOCIATED WITH THE
LOW-LEVEL JET. THE LAMONT OK AND HILLSBORO KS PROFILERS CURRENTLY
SHOW 30-35 KT OF 0-6 KM SHEAR AND THIS SHEAR MAY INCREASE SOME THIS
EVENING. THIS MAY BE SUFFICIENT FOR ISOLATED STRONG WIND GUSTS WITH
THE MORE-DEVELOPED LINE-SEGMENTS. HAIL WILL ALSO BE POSSIBLE WITH
THE THREAT PERSISTING EWD INTO SE NEB...ERN KS AND NRN OK OVERNIGHT
AS THE CONVECTION BECOMES ELEVATED AND INSTABILITY INCREASES.
...NRN UTAH/SERN ID/SW WY...
AN IMPRESSIVE UPPER-LEVEL TROUGH IS CURRENTLY LOCATED ACROSS CA AND
NV. THIS FEATURE WILL MOVE EWD ACROSS THE INTERMOUNTAIN WEST
THROUGH EARLY THIS EVENING. ISOLATED TO SCATTERED THUNDERSTORMS WILL
CONTINUE TO DEVELOP ACROSS THE REGION AS THE UPPER-LEVEL TROUGH
APPROACHES. STEEP MID-LEVEL LAPSE RATES...STRONG LARGE-SCALE ASCENT
AND STRONG VERTICAL SHEAR EVIDENT ON THE LATEST FORECAST SOUNDINGS
MAY SUPPORT A MARGINAL THREAT FOR HAIL OR STRONG WIND GUSTS LATE
THIS AFTERNOON.
..BROYLES.. 03/22/2009
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