Severe Thunderstorm Warning 17, NWS Topeka, KS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
257 PM CDT WED APR 21 1999

...SEVERE THUNDERSTORM AND HEAVY RAIN POTENTIAL INITIAL CONCERNS...
   THEN TEMPERATURES NEXT FEW DAYS...

UNSTABLE AIRMASS COVERS ENTIRE CWA EARLY THIS AFTN...BUT 18Z
SOUNDING FROM TOP SHOWS VERY STRONG CAP JUST ABOVE 800MB WITH CAP
STRENGTH AROUND 6 TO 8C. SOME ELEVATED TSTMS HAVE BEEN TRYING TO
DEVELOP PAST HR OR SO OVER THE ERN CWA...BUT ACTIVITY LOOKS WEAK
ATTM. SFC WARM FRONT ALSO BEGINNING TO LIFT INTO SERN NEBRASKA AT
19Z...SO WITH STRONG CAP IN PLACE AND SFC BOUNDARY MOVING NORTH OF
FA...APPEARS ANY TSTM DEVELOPMENT WILL OCCUR LATER THIS EVENING OR
OVERNIGHT. H7 PROFILERS SHOWING VORT MAX OVER SCENT NEBRASKA WITH
VORT LOBE EXTENDING INTO SW KS. NOT SURE IF THIS FEATURE WILL BE
ENOUGH TO BREAK STRONG CAP AT BOTH TOP AND OUN. WATER VAPOR SATL
LOOP SHOWS MORE IMPRESSIVE H5 VORT MAX WITH A MORE NEGATIVE TILT
BEGINNING TO MOVE INTO SERN NM. STRONG JET MAX ALSO SEEN
ACCOMPANYING THIS FEATURE. ALL 3 MODELS MOVE THIS VORT MAX INTO WRN
OK BY 12Z THU AND PIVOT FEATURE ACROSS ERN KS. DYNAMIC LIFT LOOKS
STRONG WITH THIS WAVE AS IT COINCIDES WITH SFC BOUNDARY BISECTING
CWA...UNSTABLE AIRMASS AND LEFT EXIT REGION OF H3 JET. SO EXPECT
THAT CONVECTION WILL BE MORE WIDESPREAD ON THU WITH THIS AMOUNT OF
FORCING. THIS WAVE MAY INITIATE TSTMS LATER TONIGHT ALONG SFC
BOUNDARY FROM CNTRL KS INTO WRN OK WITH ACTIVITY HEADING NEWRD.

WILL HOLD OFF ON ANY FLASH FLOOD WATCH FOR TONIGHT AS AM NOT REAL
CONFIDENT BULK OF THE ERN 1/2 OF THE FA WILL SEE MORE THAN 2 OF
RAIN. NCEP QPF LOOKS OVERDONE ON THE AERIAL COVERAGE OF THE 2
AMOUNTS BASED ON CAP STRENGTH FOR MUCH OF TONIGHT. WILL LOWER POPS A
TAD BUT LEAVE IN THE MENTION OF PSBL SVR/LCLY HVY PCPN.

SFC/H85 BOUNDARY THEN SAGS SOUTHWARD ACROSS THE CWA THU NITE AND
FRIDAY WITH AIRMASS BECOMING COOL AND STABLE WITH TIME. SOME
OVERRUNNING PCPN POSSIBLE THRU FRIDAY AND WILL CARRY CHC POPS FOR
THIS. BOTH FWC AND FAN GUID SHOW FAIRLY HIGH POPS NEXT FEW DAYS
ALONG WITH A COOLING TREND. FOLLOWED A COMP BETWEEN THE AVN AND NGM
SINCE THEY ARE BETTER IN THE SHORT TERM WITH THE MOVEMENT OF THE
SFC/H85 LOW.

.TOP...NONE.

BARLOW