Severe Thunderstorm Warning 1, NWS North Platte, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
147 PM CST SAT MAR 27 1999

...FORECAST PROBLEM WILL BE THUNDERSTORM POTENTIAL TONIGHT AND TEMPS...

SPLIT FLOW CONTINUES OVER THE WESTERN U.S. AS AN UPPER LEVEL LOW SPINS
OVER NORTHERN PORTIONS OF MEXICO WHILE FAST MOVING SHORTWAVES RIDE
ALONG ZONAL FLOW OVER THE NORTHERN ROCKIES.  ABUNDANT MOISTURE
STREAMING NORTH OUT OF THE GULF OF MEXICO WILL KEEP DEWPOINTS HIGH OVER
MUCH OF CENTRAL AND WESTERN NEBRASKA.  H85 DEWPOINT OF +1C WAS OVER LBF
AT 12Z.  SATELLITE IMAGERY SHOWS A DRY SLOT OVER EASTERN CO/NORTHWEST
KS/SOUTHWEST NE WHICH WILL ALLOW AFTERNOON TEMPS TO WARM ABOVE EXPECTED
READINGS WHICH SHOULD HELP DESTABILIZE THE ATMOSPHERE FOR THIS EVENING.
A WEAK FRONT AT 18Z WAS NEARLY STATIONARY FROM KVTN TO JUST WEST OF
KLBF.  THIS BOUNDARY WILL HELP TRIGGER SOME SHOWER/THUNDERSTORM
ACTIVITY EARLY THIS EVENING.

MODELS ARE IN FAIRLY GOOD AGREEMENT IN THE OVERALL TREND OF THE
FORECAST.  THERE WERE SOME TIMING AND POSITION DISCREPENCIES THOUGH.
DID LIKE THE POSITIONS OF THE SHORTWAVES AND THE MOISTURE FIELDS A
LITTLE BETTER WITH THE ETA.  THE NGM HAS BEEN OVERDOING THE
PRECIPITATION OVER THE LAST FEW RUNS.

ETA FORECAST MODEL SOUNDINGS SHOW A RELATIVELY UNSTABLE AIRMASS AT 00Z
WITH LI/S OF 0 TO -3 OVER THE SOUTHWEST CWA.  THE AFTERNOON SUN WILL
HELP REACH CONVECTIVE TEMPS.  ETA CAPES SUGGEST 200-750 J/KG AND LITTLE
OR NO CIN OVER MUCH OF SOUTHWEST NE AT 00Z.  A GOOD AREA OF Q-G
CONVERGENCE OVER WESTERN NEBRASKA AT 00Z CORRESPONDS WITH A STRONG
SHORTWAVE MOVING INTO THE PANHANDLE FROM WY.  THIS SAME SHORTWAVE HAS
TRIGGERED THUNDERSTORMS OVER THE INTERMOUNTAIN WEST MUCH OF THE NIGHT
AND INTO THE MORNING HOURS. THE MOISTURE...LIFT...AND INSTABILITY
SHOULD BE SUFFICIENT TO GET ISOLATED THUNDERSTORMS THIS EVENING.  GOOD
SUBSIDENCE AND DRYING TAKES PLACE AFTER 06Z TONIGHT SO WILL GO WITH
DECREASING CLOUDS AFTER MIDNIGHT.  THE WINDS BECOME WEST TO NORTHWEST
ACROSS THE CWA BY 06Z AS THE FRONT SAGS SOUTHEASTWARD INTO EASTERN NE.

DRY ZONAL FLOW WILL MOVE ACROSS MUCH OF CENTRAL AND WESTERN NE TOMORROW
KEEPING SKIES MOSTLY CLEAR.  A FEW CU MAY DEVELOP IN THE AFTERNOON WITH
SUN AND COLDER AIR ALOFT MOVING IN.  HOWEVER MOSTLY SUNNY SKIES SHOULD
COVER IT.  TEMPS SHOULD BE NEAR NORMAL TOMORROW AFTERNOON SO WILL STAY
CLOSE TO GUIDANCE NUMBERS.  HOWEVER WARMER SOUTHWEST FLOW DEVELOPS ON
MONDAY AS THE SFC HIGH SLIPS EASTWARD INTO MISSOURI.  THEREFORE WILL GO
A FEW DEGREES WARMER THAN THE NGM GUIDANCE SUGGESTS...BUT NOT QUITE AS
WARM THE THE FAN.

IN THE EXTENDED...A RIDGE BUILDS OVER THE CENTRAL PLAINS AS A TROF DIGS
INTO THE GREAT BASIN REGION.  THIS SHOULD BRING ABOVE NORMAL TEMPS TO
THE AREA...93P AND 94P LOOK GOOD.  THEN ON THU A SFC LOW DEVELOPS ALONG
THE FRONT RANGE WITH A WARM FRONT EXTENDING NORTHEASTWARD.  THIS COULD
SET UP SCATTERED AFTERNOON THUNDERSTORMS FOR THE CWA.  THINK THE 95P
NUMBERS LOOK REASONABLE.

.LBF...NONE

DDB