Severe Thunderstorm Warning 81, NWS Hastings, NE

SOUTH CENTRAL NEBRASKA/NORTH CENTRAL KANSAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
257 PM CDT SAT MAY 5 2001

...RAIN CHANCES MAIN CHALLENGE...AS WELL AS SVR/FLOODING POTENTIAL...

UPPER LOW CIRCULATION SHOWS UP WELL ON RADAR MOSAIC AND SATELLITE
JUST NORTHWEST OF GOODLAND.  ASSOCIATED DRY SLOT AS FAR NORTH AS
SOUTH DAKOTA BORDER.  18Z SURFACE ANALYSIS HAS LOW ALMOST UNDERNEATH
UPPER LOW...DOWN TO 998.8 MB...AND WARM FRONT ALSO APPROACHING SOUTH
DAKOTA BORDER.  SURFACE WINDS OVER CENTRAL NEBRASKA AND MOST OF
KANSAS MOSTLY SOUTH OR SOUTHWEST...BUT 2-3 MB PRESSURE FALLS ARE
BECOMING MORE COMMON THIS AFTERNOON...WHICH MAY HELP TO BACK THE
WINDS A BIT.

SURFACE WARM FRONT IS MUCH FARTHER NORTH THAN EARLIER PROGGED...
WHICH KEEPS CWFA DEEP INTO THE WARM SECTOR THIS AFTERNOON AND
EVENING.  LAPS 19Z ANALYSIS HAS CAPE VALUES UP TO 1000 J/KG IN NORTH
CENTRAL KANSAS...AND MODIFIED 18Z DDC SOUNDING SUGGESTS CAPE VALUES
UP TO 2300 POSSIBLE.  12Z H5 ANALYSIS SHOWED -21C AIR
UPSTREAM...WHICH SHOULD AT LEAST GET INTO WESTERN AREAS THIS
EVENING.  THIS INSTABILITY AND THE LIFT FROM THE UPPER LOW SHOULD BE
SUFFICIENT FOR STORM DEVELOPMENT...BUT POSSIBLY MORE SCATTERED THAN
SOLID.  ALSO STILL APPEARS THAT MORE ORGANIZED CLUSTER OF STORMS MAY
FORM TO OUR SOUTHWEST...WHICH WOULD PROVIDE ANOTHER CHANCE FOR
STORMS IN THE AREA BUT LATER IN THE EVENING/NIGHT.  CLOSELY WATCHING
VISIBLE IMAGERY FOR INITIATION TO OUR SOUTHWEST.

CURRENTLY HAVE A FLASH FLOOD WATCH POSTED FOR ERN COUNTIES...AND
GIVEN THE FLASH FLOOD GUIDANCE VALUES OF 0.5-1.0 INCHES AND A DECENT
CHANCE FOR THUNDERSTORMS...WILL NOT DROP THE WATCH BUT WILL NOT
EXPAND IT EITHER.

WITH THE WARM FRONT SO FAR NORTH AND MORE UNIDIRECTIONAL WIND
SHEAR...THE THREAT FOR WIDESPREAD SEVERE IS LESS THAN EARLIER
THOUGHTS...HOWEVER WILL CONTINUE TO MENTION SEVERE WORDING IN ZONES
WITH THREAT FOR HAIL.  AND IF SURFACE LOW CONTINUES TO DEEPEN...SOME
BACKING STILL POSSIBLE ESPECIALLY IN NEBRASKA COUNTIES AS MENTIONED
ABOVE.

BEYOND TONIGHT...WATER VAPOR LOOP SHOWS THE SHARPENING UPPER TROF
MOVING THROUGH THE PACIFIC NORTHWEST...AND MODELS ARE SIMILAR WITH
BRINGING THIS FEATURE INTO THE NORTHERN PLAINS SUNDAY NIGHT.  NGM IS
FARTHER NORTH...AND TEND TO BELIEVE THE ETA/AVN WHICH ARE IN MUCH
BETTER AGREEMENT WITH EACH OTHER.

SUNDAY THE BIG UPPER LOW TO OUR WEST WILL BEGIN TO FILL AND PHASE
WITH THE NRN STREAM LOW...HOWEVER LINGERING UPPER DIVERGENCE IN
COMBO WITH STEEP LAPSE RATES SHOULD CONTINUE TO KEEP SHOWERS IN THE
REGION.  WILL KEEP POPS FAIRLY HIGH SUNDAY...THEN TAPER SUNDAY
EVENING.  WILL ALSO MENTION WINDY ON BACK SIDE OF UPPER LOW.

LATEST MRF HAS MORE DEFINED UPPER RIDGE TAKING OVER FOR THE
WEEK...BUT KEEPS A WEAK SHORTWAVE MOVING THROUGH FOR THE END OF THE
WEEK.  THUS DRY MON-WED WITH A CHANCE THU-FRI...THEN DRY SAT.  WENT
WARMER FOR WEDNESDAY.

.GID...FLASH FLOOD WATCH TONIGHT FOR POLK...YORK...FILLMORE..
       THAYER...THAYER...NUCKOLLS...JEWELL.

NIETFELD