Tornado and Hail in Nebraska, October 9, 2001

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
238 PM CDT TUE OCT 9 2001

...THUNDERSTORM COVERAGE FORECAST CHALLENGE TONIGHT...

AT NOONTIME CDT DRIER AIR WAS FILTERING INTO THE SOUTHWEST AS A
BRIEF PERIOD OF SUBSIDENCE INCREASES WITH CLOUDS DECREASING IN THE
EXTREME SOUTHWEST. SATELLITE IMAGERY SHOWS 2 WAVES MOVING EAST ACROSS
COLORADO WITH STRONGER WAVE NOW APPROACHING THE CENTRAL PORTION OF
THE STATE. MODELS APPEAR TO BE SLOW IN THE PROGRESS OF THIS SECOND
WAVE. THE RADAR MOSAIC CURRENTLY SHOWS SHOWERS AND THUNDERSTORMS
LIFTING NORTH ACROSS THE NORTHERN FORECAST AREA...NORTH OF HIGHWAY
2. THE 18Z HAND SURFACE ANALYSIS SHOWED 1000 MB LOW JUST SOUTHWEST
OF MCK WITH DRYLINE EXTENDING SOUTH THROUGH WESTERN KANSAS. SEMI
STATIONARY FRONT EXTENDED NORTHEAST FROM LOW CENTER WEST OF A LBF
TO VTN LINE...WHILE DEVELOPING WARM FRONT POSED SOUTHEAST THROUGH
SOUTH CENTRAL NEBRASKA.

MODELS ARE IN GENERAL AGREEMENT THROUGH 60 HOURS WITH BLEND
UTILIZED. THE 15Z RUC IS SLOWER WITH THE PROGRESSION OF THE FRONT
EAST THIS EVENING WITH THE MODELS POSSIBLY UNDERESTIMATING THE IMPACT
ACROSS THE NORTH CENTRAL THROUGH 03Z. 18Z UPPER AIR SOUNDING
COMPLETED FOR LBF.

THE SURFACE LOW WILL CONTINUE TO MOVE EAST NORTHEAST WITH DRYLINE
TO OUR EAST AT 4 PM CDT. WARM FRONT TO LIFT NORTHEAST AND WASHOUT
WITH SEMI STATIONARY FRONT TO BECOME PRIMARY AREA OF LOW LEVEL
CONVERGENCE THIS EVENING ACROSS THE NORTH CENTRAL. THE 850-700 MB 2D
FRONTOGENESIS SUGGEST MAIN BOUNDARY WILL END UP ACROSS SOUTH DAKOTA
WITH H85 TROUGH TO MOVE SOUTHEAST THROUGH 03Z ACROSS FORECAST AREA
WITH INCREASING LOW LEVEL SHEAR IN THE NORTH CENTRAL WITH THREAT
FOR A FEW SEVERE STORMS EAST OF A STUART TO BROKEN BOW LINE. H85
WINDS INCREASE TO 35 TO 40 KNOTS OVERNIGHT WITH BREEZY WORDING
RETAINED OVERNIGHT. ADDITIONAL SHOWERS REDEVELOP ON THE COLD SIDE
THROUGH 06Z AS H5 WAVES LIFT NORTHEAST COMPLIMENTED BY INCREASED
DIVERGENCE ASSOCIATED WITH JETSTREAM.

WEDNESDAY HIGH PRESSURE BUILDS SOUTHEAST HOWEVER H7-H5 LAPSE RATES
WILL BE OVER 7 DEGREES C/KM WITH COLD AIR STRATOCUMULUS FIELD TO
LINGER FOR THE DAY WITH PARTLY CLOUDY SKIES SOUTHWEST AND PARTLY
SUNNY ACROSS THE NORTH WITH THE POTENTIAL FOR SOME SHOWERS
TO DEVELOP AS H5 TROUGH AXIS MOVES SLOWLY EAST WITH EMBEDDED WAVES
REMAINING IN THE FLOW. TEMPERATURES WILL STILL GET INTO THE LOW 60S
SOUTHWEST AND 55 TO 60 ACROSS THE NORTH.

WEDNESDAY NIGHT THE SURFACE HIGH BUILDS SOUTHEAST WITH LIGHT WINDS
AND DRY CONDITIONS. RETURN FLOW SETS UP IN THE WEST WITH TEMPERATURES
REBOUNDING BACK INTO THE 60S ON THURSDAY AS LEESIDE TROUGH REFORMS
NEAR THE FRONT RANGE.

THURSDAY NIGHT THE NEXT COLD FRONT SLIDES EAST WITH CHANCE OF
SHOWERS IN THE WEST BY MIDNIGHT WITH SYSTEM EAST BY FRIDAY MORNING.
FEW SHOWERS MAY STILL LINGER INTO THE MORNING WITH NO CHANGE MADE TO
CURRENT FORECAST.

IN THE EXTENDED MODELS ARE TRENDING SLOWER WITH THE H5 LONGWAVE
TROUGH WHICH MOVES INTO THE WESTERN PLAINS FRIDAY. A SPLIT IN THE
FLOW DEVELOPS SATURDAY AS H5 LOW CUTS OFF SOMEWHERE ACROSS OKLAHOMA
AND TEXAS WITH OUR FORECAST REGION BECOMING UNDER A NORTHWEST TO
WEST FLOW. A BACKDOOR COLD FRONT WILL SWING THROUGH SATURDAY BUT
WITH NORTHWEST FLOW ALOFT DEVELOPING AND MAIN FORCING WELL TO THE
NORTH WILL LEAVE DRY. SUNDAY THE NORTHWEST FLOW RE-ESTABLISHES WITH
HIGH PRESSURE TO DOMINATE AT THE SURFACE AND ALOFT WITH COLDER AIR
TO BE DRIVEN SOUTH WITH THICKNESS FALLING AS CYCLONE DROPS
SOUTHEAST ACROSS THE GREAT LAKES. COLDEST AIR CLIPS THE NORTH
CENTRAL WITH MAINLY DRY CONDITIONS INTO MONDAY AS THE SURFACE HIGH
BUILDS SOUTHEAST. THEN MONDAY SOME RECOVERY OCCURS AS WARMER
AR RETURNS AS HIGH PRESSURE BUILDS EAST ACROSS THE PLAINS THROUGH
TUESDAY.

.LBF...NONE.

KECK