Severe Thunderstorm Warning 180, NWS Hastings, NE

SOUTH CENTRAL NEBRASKA/NORTH CENTRAL KANSAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
345 PM CDT THU JUL 25 2002

...FORECAST CONCERN REMAINS TO BE THUNDERSTORM CHANCES OVER THE
NEXT SEVERAL DAYS...INCLUDING SEVERE WEATHER POTENTIAL TONIGHT...

MORNING UPPER AIR ANALYSIS AND WATER VAPOR IMAGERY PORTRAYING A
RELATIVELY NOISY LOW AMPLIFIED FLOW OVER THE CONUS. REMNANTS OF
DAMPENING UPPER RIDGE CENTERED NEAR THE FOUR CORNERS AREAS. WITH
HEIGHT FALLS PREVALENT ACROSS THE WESTERN CONUS...UPPER TROUGH
LOCATED OVER THE PACIFIC NORTHWEST...WITH ANOTHER IMPULSE HEADING OUT
OF THE GREAT BASIN INTO WYOMING. TO THE EAST...SHORTWAVE TROUGH OVER
MN/IA PHASING WITH BROADER SCALE TROUGH LOCATED OVER MANITOBA/
ONTARIO.

AFTERNOON SURFACE ANALYSIS FEATURING A WEAK LOW OVER NORTHWEST
IOWA...WITH A CONNECTING WARM FRONT THROUGH CENTRAL IA. FROM THE SFC
LOW...FRONTAL BOUNDARY/TROUGH EXTENDS ALONG THE NEB/KS BORDER TO A
HEAT AIDED SFC LOW IN NORTHWEST KS. MOISTURE CONTINUES TO POOL ALONG
AND NORTH OF THE BOUNDARY...WITH AFTERNOON DEWPOINTS AROUND 70 IN
SCNTRL NEB.

WOULD EXPECT A THUNDERSTORM COMPLEX TO DEVELOP OVER EASTERN WYOMING/
NEB PANHANDLE THIS EVENING IN PRESENCE OF EASTERLY UPSLOPE REGIME AND
APPROACHING IMPULSE THROUGH WYOMING. FURTHER ADDED INTO THE MIX WILL
BE LOW LEVEL JET THROUGH WESTERN KANSAS. PLENTIFUL ISENTROPIC
UPGLIDE WILL BE IN PLACE -- HIGHLIGHT IS IMPRESSIVE 35MB/HR PRESSURE
ADVECTION DEPICTED ON THE AFWA MM5 315 SURFACE -- THE BACKUP FOR
THE 12Z ETA RUN TODAY.

CORFIDI VECTORS SUGGEST A EASTWARD PROPAGATIONAL COMPONENT TO THE MCS
THROUGH THE CWA LATER TONIGHT -- GENERALLY PARALLELING I-80
CORRIDOR -- WITH SYSTEM SUSTAINMENT LIKELY AIDED BY EVENTUAL MCV
DEVELOPMENT. AFWA MM5 FEATURES RATHER ROBUST QPF TONIGHT...SIMILAR
TO YESTERDAYS 12Z AVN...AND TO A LESSER EXTENT YESTERDAYS 12Z ETA
RUN.

CONTINGENT UPON REALIZED PROPAGATION OF MCS...ASSOCIATED DAMAGING
WIND THREAT...AND TO A LESSER EXTENT LARGE HAIL...A POSSIBILITY WITH
THE SYSTEM. MORE THAN SUFFICIENT DEEP LAYER SHEAR PRESENT / 40-50 KTS
0-6KM / FOR SYSTEM ORGANIZATION...WITH LOW LEVEL HELICITY VALUES 300
M2/S2 PLUS.

ALSO AT LEAST SOME CHANCE FOR SCATTERED CONVECTIVE DEVELOPMENT IN THE
VICINITY OF THE TROUGH/OUTFLOW EVEN BEFORE THEORETICAL MCS REACHES
THE CWA LATER TONIGHT...THUS WILL LIKELY USE MAINLY AFTER MIDNIGHT
TO COVER THIS POSSIBILITY UNLESS PRE-ISSUANCE TRENDS DICTATE
OTHERWISE. LATEST RUC20 DOES SUPPORT CONVECTION ALONG THE BOUNDARY BY
THE 00Z TIMEFRAME. IF DEVELOPMENT DOES MATERIALIZE THIS EVENING...
ISOLATED SEVERE WEATHER THREAT EXISTS BEFORE MCS APPROACHES LATER
TONIGHT.

CONVECTIVE OUTFLOW REINFORCED TROUGH/FRONT LIKELY TO SET UP SOMEWHERE
THROUGH NORTH CENTRAL KANSAS OR SOUTH CENTRAL NEBRASKA ON FRIDAY...
BUT FINER DETAILS CAN ONLY WAIT UNTIL THEN TO BE DETERMINED. AS
HEIGHT FALLS CONTINUE ACROSS THE WESTERN CONUS AND A FEW EMBEDDED
SHORTWAVE TROUGHS APPROACH THE REGION...CONVECTIVE DEVELOPMENT AGAIN
APPEARS LIKELY BY THE LATE AFTERNOON/EVENING HOURS. SEEMINGLY A
SEVERE WX THREAT WILL EXIST FOR THE CWA.

SOMEWHAT OF A REPEAT SCENARIO ON SATURDAY...AND AGAIN ON SUNDAY AS
NEXT POTENT UPPER WAVE APPROACHES THE AREA.

IN THE EXTENDED PORTIONS OF THE FORECAST...00Z GFS AND LATEST
EUROPEAN CONSISTENT WITH PORTRAYAL OF ACTIVE TRAIN OF WESTERLIES
THROUGH SOUTHERN CANADA AND THE NORTHERN CONUS THROUGH EARLY NEXT
WEEK...WITH HINTS TOWARD INCREASED AMPLIFICATION AROUND THE MIDDLE OF
THE WEEK. BOTH MODELS FAVOR SENDING ENERGY THROUGH THE NORTHERN
PLAINS ON SUNDAY...WITH SHORTWAVE RIDGING OR ZONAL FLOW OCCURRING IN
THE WAKE OF THE AFOREMENTIONED IMPULSE. FURTHERMORE...GFS ENSEMBLE
MEMBERS ALSO LARGELY SUPPORTIVE OF THIS TIMING. THUS...DRY FORECAST
PREVAILS MONDAY ONWARD...WITH TEMPERATURES AROUND OR ABOVE SEASONAL
NORMS.

.GID...NONE

GUYER

KSZ005>007-017>019-260300-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE HASTINGS NE
934 PM CDT THU JUL 25 2002

SEVERE THUNDERSTORM WATCH NUMBER 533...IN EFFECT UNTIL MIDNIGHT FOR
JEWELL...MITCHELL...OSBORNE...PHILLIPS...ROOKS...AND SMITH COUNTIES
IN NORTH CENTRAL KANSAS...HAS BEEN CANCELLED.

ADDITIONAL SHOWERS AND THUNDERSTORMS ARE POSSIBLE OVERNIGHT...BUT
THE THREAT FOR SEVERE WEATHER HAS ENDED THIS EVENING.

07