FXUS65 KBOU 251030
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER CO
330 AM MST FRI DEC 25 2009

.SHORT TERM...WE ARE STARTING TO SEE THE WINDS INCREASE ACROSS THE 
PLAINS THIS MORNING WITH GUSTS TO 31 KTS AT KAKO THIS PAST HOUR.  
ROAD REPORTS FROM CDOT ALSO INDICATE WINDY CONDITIONS IN THE 
MOUNTAINS AND FOOTHILLS AND DOWN TO WESTERN SUBURBS OF DENVER.  
SINCE THE MORNING IS STARTING OFF WINDY...WITH VERY LITTLE EVIDENCE 
OF ANY NOCTURNAL INVERSION...THE QUESTION BECOMES HOW WINDY IT MIGHT 
EVENTUALLY GET.  SURFACE WIND FORECASTS FROM THE NAM12 ONLY INDICATE 
5 TO 10 KNOTS MORE THAN WHAT WE ARE SEEING NOW.  WE SEEM TO STILL 
HAVE A LITTLE ROOM BEFORE GOING OVER HIGH WIND CRITERIA.  THE MAIN 
MESSAGE FOR THE DAY IS GOING TO BE THE BLOWING AND DRIFTING SNOW 
CAUSED BY THE WINDS.  WINTER WEATHER ADVISORY WILL GO INTO EFFECT AT 
5 AM AND LAST THROUGH SATURDAY MORNING.  TEMPERATURES SHOULD WARM 
ONLY SLIGHTLY THROUGH THE DAY AS THE NORTHWESTERLY FETCH WILL 
CONTAIN NEITHER WARM OR COLD ADVECTION.  ONE OTHER UNKNOWN IS 
WHETHER OR NOT SNOWFALL FROM MOISTURE WRAPPING AROUND THE NORTH SIDE 
OF THE UPPER LOW WILL MAKE IT INTO THE FORECAST AREA.  SATELLITE 
PICTURES ARE INDICATING SOME DEVELOPING CLOUDS OVER SOUTHEAST 
WYOMING WHICH SHOULD BE ABLE TO GENERATE SOME SNOW SHOWERS.  
ADJUSTED POPS ON THE PLAINS DOWN A LITTLE BIT TODAY...BUT HELD ONTO 
SCATTERED POPS LATER TONIGHT.  LOOKS LIKE THE WINDS WILL CONTINUE 
BLOWING THROUGH TONIGHT BEFORE THE GRADIENT SLACKENS ON SATURDAY AND 
SPEEDS BEGIN COMING DOWN.  WINDY CONDITIONS HAVE BEEN THE MAIN 
MESSAGE IN THE FORECAST FOR A COUPLE DAYS NOW...AND IT CERTAINLY 
LOOKS LIKE TODAY WILL BE A GOOD DAY TO BE INSIDE.  

.LONG TERM...INTENSE STORM SYSTEM WILL SLOWLY MOVE EASTWARD OUT OF 
THE CENTRAL PLAINS ON SAT HOWEVER NRN CO WILL STILL BE AFFECTED BY 
THIS MASSIVE SYSTEM.  THE FLOW ALOFT WILL BE NNE ACROSS THE AREA 
WITH QUITE A BIT OF MOISTURE SHOWN ABOVE 700 MB.  LOW LEVEL FLOW 
WILL REMAIN NNW ACROSS NERN CO SO BEST CHC OF SOME LIGHT SNOW WILL 
BE OVER THE PLAINS AS A DISTURBANCE MOVES SOUTHWARD ACROSS THE 
AREA.  WITH BNDRY LEVEL FLOW AROUND 40 KTS GUSTY WINDS AND AREAS OF 
BLOWING SNOW WILL STILL BE POSSIBLE OVER PORTIONS OF THE PLAINS 
ESPECIALLY ALONG THE CO-NE BORDER AREA.  IN THE MTNS 700 MB WINDS 
ARE FCST TO HAVE A SLIGHT NWLY COMPONENT SO MAY SEE SOME LIGHT 
OROGRAPHIC SNOW AS LAPSE RATES WILL BE RATHER STABLE.  TEMPS ON SAT 
MAY RISE A FEW DEGREES CLOSER TO THE FOOTHILLS WHILE OVER THE PLAINS 
HIGHS MAY NOT CHANGE MUCH FROM FRIDAY.  FOR SAT NIGHT MAY STILL SEE 
A SOME LIGHT SNOW LINGER OVER THE FAR NERN PLAINS IN THE EARLY 
EVENING HOURS WITH GUSTY WINDS SUBSIDING SOMEWHAT AFTER SUNSET.  IN 
THE MTNS CROSS-SECTIONS STILL SHOW SOME POTENTIAL FOR SCT -SHSN 
OVERNIGHT.  

BY SUN THE FLOW ALOFT AND AT THE SFC WILL BEGIN TO WEAKEN HOWEVER 
CROSS-SECTIONS STILL SHOW SOME LOW LVL MOISTURE LINGERING IN THE 
MTNS AND OVER THE PLAINS.  AT THIS TIME WILL KEEP FCST DRY ALTHOUGH 
ANOTHER WEAK DISTRUBANCE IS FCST TO MOVE ACROSS THE AREA.  TEMPS ON 
SUN SHOULD RISE A FEW DEGREES BASED ON LATEST 850-700 MB TEMPS 
HOWEVER THEY WILL STILL BE BELOW NORMAL.  FOR MON AN UPPER LEVEL 
HIGH WILL DVLP OVER THE NRN ROCKIES WITH WEAK FLOW ALOFT ACROSS NRN 
CO AND RATHER DRY AIRMASS.  850-700 MB TEMPS DO NOT CHANGE MUCH ON 
MON SO WILL KEEP HIGHS MAINLY IN THE LOWER TO MID 30S ACROSS THE 
PLAINS.  

BY MON NIGHT INTO TUE A WEAK UPPER LEVEL TROUGH WILL MOVE ACROSS THE 
AREA WHICH MAY PRODUCE A CHC OF SOME LIGHT SNOW IN THE MTNS.  OVER 
NERN CO THE SFC PTRN IS NOT FAVORABLE FOR PCPN AS THERE IS NO 
UPSLOPE FLOW AS LOW LVL FLOW IS WLY.  HIGHS ON TUE MAY END UP A 
DEGREE OR TWO WARMER BUT STILL REMAIN BLO SEASONAL LEVELS.  FOR WED 
AND THU NWLY FLOW ALOFT WILL BE OVER THE AREA.  CROSS-SECTIONS SHOW 
THERE WILL BE SOME POTENTIAL FOR OROGRAPHIC SHSN IN THE MTNS BOTH 
DAYS WITH FAVORABLE NWLY FLOW AT 700 MB.  OVER NERN CO THE ECMWF AND 
GFS DIFFER SOMEWHAT AS THE ECMWF HAS A CDFNT AFFECTING THE AREA ON 
THU WHILE THE GFS DOES NOT.  THIS FAR OUT HARD TO SAY WHICH SOLUTION 
IS CORRECT SO SEE NO REASON TO CHANGE CURRENT FCST.   

&&

.AVIATION...VFR CONDITIONS EXPECTED THROUGH TONIGHT THOUGH THERE IS 
A CHANCE OF CEILINGS PRECLUDING VISUAL APPROACHES ON THIS AFTERNOON 
AND TONIGHT. NORTHWEST WINDS GUSTING AOA 30 KNOTS ARE EXPECTED FROM 
LATE THIS MORNING THROUGH TONIGHT. SHOULD NOT BE TOO MUCH OF A 
CROSSWIND THREAT AT KDEN BUT THERE WILL LIKELY BE SOME DRIFTING SNOW.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...WINTER WEATHER ADVISORY FOR THE   
      NORTHEAST COLORADO PLAINS FROM 5 AM MST TODAY THROUGH 5 AM MST
      SATURDAY...ZONES 42..44..48..49..50..51.

$$

KDRBY/RPK