FXUS63 KGLD 240458
AFDGLD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GOODLAND KS
958 PM MST WED DEC 23 2009

.DISCUSSION...
207 PM MST WED DEC 23 2009

THE 20Z SURFACE ANALYSIS PLACES LOW PRESSURE OVER 
SOUTHWEST TEXAS WITH A LOBE EXTENDING NORTHEAST INTO EASTERN KANSAS. 
WATER VAPOR IMAGERY SHOWS THE MAIN UPPER LOW STILL DIGGING SOUTH AND 
IS CURRENTLY CENTERED OVER SOUTHCENTRAL NEW MEXICO. THE NORTHERN 
TROUGH IS MOVING SOUTHEAST AND IS OVER CENTRAL MONTANA. KGLD RADAR 
AND METARS SHOWING WIDESPREAD LIGHT SNOW ACROSS THE FORECAST AREA. 
SNOW AMOUNTS RANGING FROM 1 TO 3 INCHES ACROSS A LARGE PART OF THE 
AREA WITH HIGHER AMOUNTS OF 6+ INCHES IN LOGAN AND GOVE COUNTIES AS 
WELL AS CHEYENNE COUNTY COLORADO.

THE NAM SHOWS THE UPPER LOW OPENING UP INTO A TROUGH TONIGHT AND 
THEN INTENSIFYING SOME OVER SOUTHERN OKLAHOMA/NORTHERN TEXAS ON THURSDAY. 
BY THURSDAY NIGHT THE LOW WILL MOVE INTO EASTERN OKLAHOMA WITH ANOTHER 
LOW OVER NORTHEAST WYOMING. THESE TWO LOWS WILL THEN COMBINE INTO 
ONE LOW OVER NORTHERN IOWA ON FRIDAY. THE LOW WILL MOVE INTO 
NORTHEAST IOWA ON SATURDAY. THE SURFACE LOW WILL MOVE INTO EASTERN 
OKLAHOMA TONIGHT AND THEN INTO MISSOURI/ARKANSAS ON THURSDAY. BY 
THURSDAY NIGHT THE LOW WILL SHIFT INTO NORTHEAST MISSOURI. ON FRIDAY 
THE LOW WILL MOVE INTO NORTHERN IOWA.

MAIN ISSUES WITH FORECAST ARE MAKING MODIFICATIONS TO THE CURRENT 
HIGHLIGHT TO BETTER FIT NEW MODEL AND REAL TIME DATA.

BOTH THE GFS/NAM INDICATE THAT MAIN DYNAMICS/PRECIPITATION WILL BE 
EAST OF THE FORECAST AREA THU/THU NIGHT. HOWEVER WINDS SPEEDS AROUND 
26KTS ARE INDICATED WHICH WILL CAUSE CONSIDERABLE BLOWING SNOW. EVEN 
THOUGH VERY LITTLE NEW SNOW WILL FALL ON THURSDAY/THURSDAY NIGHT THERE 
WILL ALREADY BE SEVERAL INCHES OF SNOW ACROSS THE FORECAST AREA SO 
HAVE DECIDED TO DOWNGRADE THE WINTER STORM WARNING TO A WINTER 
WEATHER ADVISORY FOR BLOWING SNOW. THIS WILL REPLACE THE WARNING 
FROM 12Z THU TO 12Z FRI. SEE DETAILS BELOW.

THERE IS A WAVE THAT ROTATES AROUND THE UPPER LOW WHICH WILL AFFECT 
THE FORECAST AREA ON FRIDAY. PLAN TO GO WITH CHANCE POPS FOR LIGHT 
SNOW. WINDS WILL ONCE AGAIN BE THE MAIN EMPHASIS HERE SO WILL GO 
WITH ONLY AREAS OF BLOWING SNOW SINCE MUCH OF THE SNOW WILL ALREADY 
HAVE BLOWN INTO DITCHES AND BE PACKED SOMEWHAT FROM THE WIND ON 
THURSDAY. HOWEVER A WIND ADVISORY MIGHT BE NEEDED FOR FRIDAY BUT DO 
NOT WANT TO HOIST IT NOW SINCE IT IS IN THE 4TH PERIOD AND TO AVOID 
COMPLICATING CURRENT HIGHLIGHTS. SNOW CHANCES DECREASE FRIDAY NIGHT 
AS THE SHORTWAVE MOVES SOUTH OF THE AREA AND THE UPPER LOW MOVES 
EAST. SUBSIDENCE MOVES IN SATURDAY/SATURDAY NIGHT SO THE FORECAST 
WILL BE DRY WITH NIL POPS.

TEMPERATURES ARE GOING TO BE SUBJECT TO THE EXTENT OF THE SNOW FIELD 
WHICH SHOULD BE OVER THE ENTIRE FORECAST AREA. CONSEQUENTLY WILL 
LEAN TOWARD THE COLDEST GUIDANCE FOR MAX/MIN TEMPERATURES.

IN THE EXTENDED...THE GFS AND THE ECMWF SHOW ANOTHER STORM COMING AT 
THE FORECAST AREA DEC 29. SINCE THAT IS IN THE DAY 6,7 PERIODS WILL 
KEEP DRY FOR NOW AND WILL WAIT FOR ADDITIONAL MODEL RUNS. OTHERWISE 
A SHORTWAVE RIDGE BUILDS INTO THE PLAINS WITH DRY CONDITIONS FOR 
DAYS 4 AND 5. MAX TEMPERATURES WILL BE SUBJECT TO THE SNOW FIELD 
WITH READINGS ABOUT 10 TO 12 DEGREES BELOW NORMAL IN THE UPPER 20S. 
MIN TEMPERATURES WILL ALSO BE ABOUT 5 DEGREES BELOW NORMAL IN THE 
LOWER TEENS.

FS
&&

.AVIATION...
955 PM MST WED DEC 23 2009

FOR THE 06Z TAFS...VARIABLE FLIGHT CONDITIONS CURRENTLY EXIST IN
THE AREA AS THE LAST OF THE SNOW WINDS DOWN OVER THE NEXT 2-4
HOURS. MAIN AVIATION CONCERN DURING MUCH OF THE TAF PERIOD WILL BE
INCREASED WIND SPEEDS IN THE NEIGHBORHOOD OF 30G40KTS AT TIMES
DURING THE COURSE OF THE DAY ON THURSDAY. FOR THIS REASON, HAVE
OPTED TO INCLUDE MVFR VIS AND BLSN AT BOTH SITES UNTIL ROUGHLY
SUNSET WHEN WIND SPEEDS WILL DECREASE DRAMATICALLY AT THE SURFACE,
YET REMAIN RELATIVELY STRONG A FEW HUNDRED FEET OFF THE SURFACE.

50
&&

.GLD WATCHES/WARNINGS/ADVISORIES...
KS...WINTER WEATHER ADVISORY FROM 5 AM MST /6 AM CST/ THURSDAY TO 5 
     AM MST /6 AM CST/ FRIDAY FOR KSZ001>004-013>016-027>029-041-
     042.

     WINTER STORM WARNING UNTIL 5 AM MST /6 AM CST/ THURSDAY FOR 
     KSZ001>004-013>016-027>029-041-042.

NE...WINTER WEATHER ADVISORY FROM 5 AM MST /6 AM CST/ THURSDAY TO 5 
     AM MST /6 AM CST/ FRIDAY FOR NEZ079>081.

     WINTER STORM WARNING UNTIL 5 AM MST /6 AM CST/ THURSDAY FOR 
     NEZ079>081.

CO...WINTER WEATHER ADVISORY FROM 5 AM THURSDAY TO 5 AM MST FRIDAY 
     FOR COZ090>092.

     WINTER STORM WARNING UNTIL 5 AM MST THURSDAY FOR COZ090>092.

&&

$$