DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 200100
SWODY1
SPC AC 200058

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0758 PM CDT SAT MAY 19 2007

VALID 200100Z - 201200Z

..THERE IS A SLGT RISK OF SVR TSTMS TONIGHT OVER PORTIONS OF THE
NRN HIGH PLAINS...

..NRN HIGH PLAINS...

LATEST MESOANALYSIS INDICATES LOW-LEVEL BAROCLINIC ZONE STRETCHING
FROM SURFACE LOW N OF BZN GENERALLY EWD THROUGH CNTRL MT AND THEN
MORE SHARPLY SEWD FROM SERN MT INTO SWRN SD OR THE NWRN NEB PNHDL.
AS OF 0030Z...TSTMS WERE WIDELY SCATTERED FROM VICINITY OF THIS
SURFACE LOW EWD TO JUST W OF MLS. MUCH OF THIS ACTIVITY HAS
STRUGGLED TO SUSTAIN ITSELF SO FAR THIS AFTERNOON AND
EVENING...THOUGH SOME INTENSIFICATION HAS RECENTLY OCCURRED WITH
LARGER COMPLEX W OF MLS.

00Z REGIONAL SOUNDINGS AND RUC OBJECTIVE FIELDS INDICATE THE
PRESENCE OF RELATIVELY STEEP LOW TO MID-LEVEL LAPSE RATES WHICH WERE
CONTRIBUTING TO POCKETS OF MODERATE INSTABILITY WITH MLCAPES OF
1000-1500 J/KG. MOREOVER...THE LEADING EDGE OF STRONG MID-LEVEL JET
ATTENDANT TO SHORT WAVE TROUGH OVER THE PACIFIC NW IS BEGINNING TO
SPREAD E OF THE CONTINENTAL DIVIDE...ATOP LOW-LEVEL ELY FLOW TO THE
N OF FRONTAL ZONE. RESULTING DEEP LAYER VERTICAL SHEAR IS
SUFFICIENT /I.E. EFFECTIVE BULK SHEAR OF 45-55 KT/ TO SUPPORT
SUPERCELLS AND/OR BOWING STRUCTURES CAPABLE OF DAMAGING WINDS AND
LARGE HAIL.

STORMS MAY TEND TO MERGE INTO LARGER CLUSTERS LATER THIS EVENING
WITH THE DAMAGING WIND AND HAIL THREAT SPREADING EWD TOWARD THE WRN
DAKOTAS.

..CNTRL HIGH PLAINS...

CLUSTERS OF TSTMS ARE ONGOING THIS EVENING OVER THE PLAINS OF ERN CO
NEWD THROUGH CNTRL NEB TO SERN SD ALONG AND S OF ERN EXTENSION OF
NRN HIGH PLAINS FRONTAL ZONE. 00Z SOUNDING FROM LBF ALSO SHOWED
STEEP LOW/MID-LEVEL LAPSE RATES AND MODEST BOUNDARY LAYER MOISTURE
WHICH WERE CONTRIBUTING TO MLCAPES OF AROUND 1500 J/KG.
HOWEVER...THIS REGION IS DISPLACED WELL TO THE SE OF THE STRONGER
MID-LEVEL FLOW CRESTING THE NRN ROCKIES WITH DEEP LAYER VERTICAL
SHEAR OF GENERALLY 20-25 KT.

GIVEN THE MARGINAL VERTICAL SHEAR AND ABSENCE OF ANY APPRECIABLE
LARGE-SCALE FORCING FOR ASCENT...EXPECT ONGOING STORMS TO BEGIN TO
WEAKEN AFTER 03-04Z AS BOUNDARY LAYER AND LAPSE RATES WEAKEN.
HOWEVER PRIOR TO THIS...THE MORE INTENSE STORMS WILL REMAIN CAPABLE
OF ISOLATED STRONG WIND GUSTS AND SOME SEVERE HAIL.

.MEAD.. 05/20/2007

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