Severe Thunderstorm Warning 221, NWS North Platte, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
150 PM CDT SUN AUG 25 2002

...TRYING TO PIN DOWN TIMING ON CONVECTION AS SPRINGTIME SEVERE WX
PATTERN ARRIVES ABOUT FOUR MONTHS LATE...

NOTE: ZONES WILL PROBABLY BE OUT LATE AS SVR WX AND NUMEROUS UPDATES
HAVE LEFT ME BEHIND SCHEDULE.

SYNOPSIS...LEE/INVERTED TROUGH EXTENDS NORTHWARD FROM A LOW PRESSURE
CENTER OVER SE COLORADO AT 17Z.  IN ADDITION A MESO HIGH FROM THE
MORNING CONVECTION HAS DEVELOPED OVER CENTRAL NEBRASKA.  TIGHT
PRESSURE GRADIENT BETWEEN THESE TWO SYSTEM LEADING TO A RATHER
BRISK SOUTHERLY FLOW ACROSS THE WESTERN CWA...WITH 60 DEGREE
DEWPOINTS BEING ADVECTED INTO THE AREA.

DISCUSSION...FAIRLY BUSY AFTERNOON SETTING UP WITH STRONG
INSTABILITY OVER THE WESTERN HALF OF THE CWA...STRONG VERTICAL SHEAR
AND AN OUTFLOW FROM MORNING THIS MORNING TO FOCUS THINGS.
AFTERNOON/EVENING ACTIVITY SHOULD EVOLVE INTO AN MCS OVERNIGHT...
HOWEVER MODELS REALLY DONT SEEM TO HAVE A HANDLE ON ONGOING
CONVECTION SO WILL WORD TONIGHT BASED ON LAST MINUTE RADAR TRENDS.

TOMORROW WILL BE COMPLICATED BE HOW/WHERE CONVECTION FORMS/MOVES
TONIGHT.  12Z RUN OF THE ETA HAS CONVECTIVE COMPLEX OVER US DURING
THE DAY KEEPING TEMPS DOWN AND CLOUDS AROUND ALL DAY.  FIND IT HARD
TO BELIEVE THE ETA HAS THE RIGHT IDEA...HOWEVER REALLY CANT RULE
IT OUT.  WITH AVN SOLUTION OF A WEAK FRONT ACROSS THE NORTHERN CWA
AND WITH THE THE NEAR CERTAINTY OF LEFT OVER BOUNDARIES IN THE AREA
WILL PROBABLY CARRY 30-40 POP AREA WIDE SINCE I REALLY CANT
PINPOINT A SPECIFIC LOCATION THIS FAR OUT.  ALSO WITH THREAT OF AM
CONVECTION WILL NOT GET CUTE WITH TIMING EITHER.

LLJ SHOULD NOSE INTO SW NEBRASKA TOMORROW NIGHT SO AN MCS COULD
CERTAINLY TRAVERSE PORTIONS OF THE CWA...BUT AGAIN EVERYTHING IS SO
DEPENDENT ON MESOSCALE FEATURES SO REALLY CANT GET ALL THAT
SPECIFIC WITH TIMING OR LOCATION.

THE BROKEN RECORD CONTINUES THURSDAY AND THURSDAY NIGHT WITH SFC
BOUNDARIES IN THE AREA AND PLENTY OF INSTABILITY...SO ANOTHER DAY
OF 30 POPS SEEMS TO BE JUSTIFIED.  TEMPS WILL AGAIN BE DEPENDENT ON
THE AMOUNT OF DEBRIS CLOUDINESS AND WHETHER ANY CONVECTION LINGERS
INTO THE LATE MORNING.  GIVEN THAT MUCH OF WEATHER WILL BE
CONTROLLED BY MESOSCALE FEATURES THE NEXT FEW DAYS REALLY CANT
JUSTIFY MAKING MANY CHANGES TO THE GOING FORECASTS TEMPS.

EXTENDED...GLOBAL MODEL PRETTY INSISTENT ON BUILDING THE UPPER RIDGE
NORTHWARD INTO THE HIGH PLAINS THIS WEEKEND.  APPEARS AS THOUGH THE
SUBTROPICAL JET MAY BUILD NORTHWARD FRIDAY AND SATURDAY IN RESPONSE
TO THE BUILDING RIDGE.  AT THE SURFACE APPEARS AS THOUGH LEE TROUGH
WILL SET UP FOR MUCH OF THE EXTENDED WITH LARGE SURFACE HIGH OVER
THE EASTERN CONUS.

SOUTH TO SOUTHEAST LOW LEVEL WINDS SHOULD SUPPLY MOISTURE TO THE AREA
WITH AFTERNOON HIGHS APPROACHING THE CONVECTIVE TEMP LOOKS LIKE PM TS
A GOOD BET.  GOING POPS FRIDAY LOOK GOOD.  A FAIRLY GOOD ARGUMENT
COULD PROBABLY BE MADE FOR INTRODUCING LOW CHANCE POPS TROUGHOUT THE
EXTENDED.  HOWEVER PREVIOUS RUN HAD THE TROUGH PULLING OUT OF THE
AREA SUNDAY AND MONDAY.  CONSIDERING THE ONGOING DROUGHT WILL ONLY
INTRODUCE POPS ON SATURDAY.

LOOKS LIKE A FAIRLY WARM WEEKEND COMING WITH TEMPS LIKELY RUNNING
ABOVE CLIMO. CONSIDERING THE MEX/FMR HAVE A COOL BIAS IN THE OUTER
PERIODS WILL GO AHEAD AND BUMP THE TEMPS IN THE EXTENDED UP A
CATEGORY OR SO.

.LBF...NONE.

IZZI/44

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORTH PLATTE, NE
258 PM CDT MON AUG 26 2002

TIME(CDT)  .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0220 PM    4 N MERRIMAN              NE   1.75 INCH HAIL
08/26/02   WESTERN CHERRY

0230 PM    MERRIMAN                  NE   1.50 INCH HAIL
08/26/02   WESTERN CHERRY

JCB

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORTH PLATTE, NE
309 PM CDT MON AUG 26 2002

TIME(CDT)  .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0230 PM    MERRIMAN                  NE   1.75 INCH HAIL
08/26/02   WESTERN CHERRY

JCB

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORTH PLATTE, NE
325 PM CDT MON AUG 26 2002

TIME(CDT)  .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0210 PM    5 WSW MERRIMAN            NE   .75 INCH HAIL
08/26/02   WESTERN CHERRY

TRM

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORTH PLATTE, NE
328 PM CDT MON AUG 26 2002

TIME(CDT)  .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0130 PM    MERRIMAN                  NE   1.75 INCH HAIL
08/26/02   WESTERN CHERRY

TRM

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORTH PLATTE, NE
333 PM CDT MON AUG 26 2002

TIME(CDT)  .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0220 PM    4 N MERRIMAN              NE   1.75 INCH HAIL
08/26/02   WESTERN CHERRY

0230 PM    MERRIMAN                  NE   1.50 INCH HAIL
08/26/02   WESTERN CHERRY

0230 PM    MERRIMAN                  NE   1.75 INCH HAIL
08/26/02   WESTERN CHERRY

TRM

NEZ004>010-022>029-035>038-056>059-069>071-094-262045-

HAZARDOUS WEATHER OUTLOOK FOR WESTERN AND NORTH CENTRAL NEBRASKA
NATIONAL WEATHER SERVICE NORTH PLATTE NE
345 PM CDT MON AUG 26 2002

...STORM SPOTTER ACTIVATION WILL BE REQUIRED ACROSS WESTERN AND NORTH
CENTRAL NEBRASKA THIS AFTERNOON AND TONIGHT...

AN UNSTABLE MOIST ATMOSPHERE WILL PERSIST ACROSS THE OUTLOOK AREA
THIS AFTERNOON INTO TONIGHT. A LEE SIDE TROUGH REMAINS STATIONARY
FROM EASTERN COLORADO INTO THE NEBRASKA PANHANDLE.  IN ADDITION...
THUNDERSTORMS WHICH OCCURRED THIS MORNING OVER NORTH CENTRAL
NEBRASKA LAID DOWN FURTHER SURFACE BOUNDARIES TO FOCUS ADDITIONAL
THUNDERSTORM DEVELOPMENT THIS AFTERNOON AS TEMPERATURES RISE...AND AN
UPPER LEVEL DISTURBANCE ENTERS THE REGION.  THE ATMOSPHERE WILL
SUFFICIENTLY DESTABILIZE TO BRING US ANOTHER ROUND OF SEVERE
THUNDERSTORMS LATER THIS AFTERNOON INTO TONIGHT. LARGE HAIL AND
DAMAGING STRAIGHT LINE WINDS WILL BE THE PRIMARY THREAT THIS
AFTERNOON AND TONIGHT.

SEVERE WEATHER IS POSSIBLE ACROSS ALL OF WESTERN AND NORTH CENTRAL
NEBRASKA THIS AFTERNOON INTO TONIGHT.