FXUS63 KGID 292315
AFDGID

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
515 PM CST SUN NOV 29 2009

.AVIATION...00Z TAF. VFR CONDITIONS SHOULD BE EXPECTED AT
KGRI WITH NO VISIBILITY OR CEILING RESTRICTIONS. SOME PASSING
MID LEVEL CLOUDS THIS EVENING...AND CIRRUS DURING THE DAY
MONDAY WILL BE THE ONLY CLOUDS AROUND. WINDS WILL SETTLE INTO
A LIGHT WEST/SOUTHWEST RHYTHM AT SPEEDS OF LESS THAN 12KTS.

&&

.PREV DISCUSSION... /ISSUED 248 PM CST SUN NOV 29 2009/

SHORT TERM...TONIGHT THROUGH 12Z TUESDAY. MAIN FORECAST CONCERN
WILL BE TEMPERATURES.

A WEAK SURFACE HIGH IS TRYING TO PUSH INTO THE AREA THIS AFTERNOON
AND ALLOWING FOR CLEAR SKIES AND LIGHT WINDS. NORTHWEST FLOW TONIGHT
WILL BECOME MORE ZONAL THROUGH MONDAY NIGHT. THE SURFACE HIGH THAT
TRIES TO PUSH INTO THE AREA TODAY WILL SLIDE TO THE SOUTH AND WINDS
WILL GRADUALLY TURN TO THE WEST. WARM ADVECTION STARTS TONIGHT AND
CONTINUES THROUGH THE PERIOD. WITH WARM ADVECTION...DOWN-SLOPE WINDS
AND 850MB TEMPERATURES WARMING NEARLY 10 DEGREES BETWEEN NOW AND 12Z
TUESDAY TEMPERATURES AT THE SURFACE SHOULD ALSO WARM UP SOME. IN
ADDITION THERE IS LITTLE TO NO MOISTURE THROUGH MUCH OF THE
ATMOSPHERE AND EXPECT THAT SKIES SHOULD BE MOSTLY CLEAR THROUGHOUT
THE PERIOD.

LONG TERM...12Z TUESDAY THROUGH NEXT SUNDAY.

AS THE AREA HEADS INTO TUESDAY...THE MODELS CONTINUE TO POINT TOWARD
TUESDAY BEING THE LAST MILD DAY FOR THE NEXT SEVERAL. THE REGION IS
STUCK BETWEEN A CLOSED LOW SPINNING SLOWLY EAST OVER THE SOUTHERN
PLAINS WHILE A PROGRESSIVE NORTHERN STREAM WAVE IS SEEN SLIDING EAST
OVER THE NORTHERN PLAINS. THE DIRECT CIRCULATION ASSOCIATED WITH A
100+KT UPPER JET STREAK AHEAD OF THE NORTHERN PLAINS WAVE WILL AID
IN PUSHING A COLD FRONT INTO THE REGION BY MID AFTERNOON...HOWEVER
AHEAD OF THIS FRONT A MILD MORNING TO EARLY AFTERNOON WILL PREVAIL
WITH WAA PUSHING 850MB TEMPERATURES INTO A +6 TO +12C RANGE TO START
THE DAY. GIVEN DECENT MIXING AND SUNSHINE EXPECTED AHEAD OF THE
FRONT...WILL AIM FOR HIGHS IN THE MID TO UPPER 50S FOR TUESDAY.

THE CONSENSUS AMONG THE MODELS REMAINS SIMILAR FOR TUESDAY NIGHT
INTO WEDNESDAY/THURSDAY AS THE WEATHER PATTERN IS SHOWN TO TAKE A
SHARP NOSE DIVE TEMPERATURE WISE. THE AFOREMENTIONED NORTHERN STREAM
WAVE IS SHOWN TO MERGE WITH THE SOUTHERN STREAM CLOSED CIRCULATION
TO FORM A PHASED UPPER TROUGH FROM THE HUDSON BAY REGION INTO THE
LOWER MS RIVER VALLEY. THIS PHASED UPPER TROUGH WILL CONTINUE TO
ALLOW MODIFIED ARCTIC AIR TO SPILL SOUTHWARD OUT OF CANADA WITH THE
COLD FRONT PLOWING INTO THE AREA TUESDAY AFTERNOON...SURGING SOUTH
TO THE GULF COAST AREA BY WEDNESDAY AFTERNOON. ALTHOUGH STRONG CAA
WILL EXIST BEHIND THE FRONT...MID LEVEL FRONTOGENETIC FORCING IS
SHALLOW AND VERY PROGRESSIVE WHILE THE ENTIRE PERIOD IS DOMINATED BY
ISENTROPIC DOWNGLIDE.  THIS ALONG WITH A FAIRLY DRY LOWER 10 KFT OF
THE ATMOSPHERE...INDICATES PRECIPITATION CHANCES WILL BE SLIM AT
BEST. BASED ON THIS ASSESSMENT...WILL KEEP A DRY FORECAST FOR
TUESDAY NIGHT THROUGH THURSDAY. THE BIGGER HEADLINE FOR WEDNESDAY
AND THURSDAY IS THE DRAMATIC DROP IN TEMPERATURES BEHIND THE FRONT
COMPARED TO TUESDAY AS 850MB TEMPERATURES ARE PROGGED TO FALL INTO A
-6C TO -11C RANGE BY WEDNESDAY NIGHT INTO THURSDAY.
NONETHELESS...MINIMAL CLOUD COVER WILL PROVIDE FOR DECENT INSOLATION
AND SUBSEQUENT MIXING AS TEMPERATURES TOP OUT IN THE 30S.

MANY QUESTIONS THEN EXIST FOR LATE FRIDAY INTO THE WEEKEND AS THE
MEDIUM RANGE MODELS CONTINUE TO DISPLAY A WIDE SPREAD IN POSSIBLE
SOLUTIONS WITH THE EVOLUTION OF THE UPPER PATTERN ACROSS THE WESTERN
HALF OF THE CONUS. THE MODELS GENERALLY ATTEMPT TO DIG A TROUGH INTO
THE WESTERN CONUS WHILE KICKING THE EASTERN CONUS TROUGH TO EITHER
THE EAST COAST OR INTO THE ATLANTIC. HOWEVER...THE AMPLITUDE AND
AMOUNT OF PHASING OF THE WESTERN CONUS TROUGH ARE COMPLETELY
DIFFERENT ALONG WITH TIMING DIFFERENCES OF 24-48 HOURS FROM ONE RUN
TO THE NEXT LET ALONE COMPARED TO OTHER MODELS. THE ECMWF AND GFS
ENSEMBLE DATA SUPPORTS THIS CHAOTIC SET OF OUTCOMES OVER THE WESTERN
CONUS AS ENSEMBLE MEMBERS SHOW LITTLE IF ANY TRENDS. GIVEN ALL OF
THIS INFORMATION...CONTINUE TO HAVE LITTLE CONFIDENCE IN PICKING ANY
OF THESE SOLUTIONS AND WILL OPT TO GO CLOSER TO A
PERSISTENCE/SLIGHTLY BELOW CLIMO FORECAST FOR FRIDAY INTO THE WEEKEND
WHICH RESULTS IN HIGHS STAYING IN THE 30S...BUT THIS COULD OBVIOUSLY
BE 10 TO 20 DEGREES TOO WARM OR COLD.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&

$$