FXUS65 KBOU 261046
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER CO
346 AM MST SAT DEC 26 2009

.SHORT TERM...MOISTURE CONTINUES TO WRAP AROUND INTENSE STORM SYSTEM 
OVER THE UPPER MIDWEST INTO NRN COLORADO AND WILL REMAIN OVER THE 
AREA THROUGH TONIGHT.  APPEARS A DISTURBANCE IN NORTH TO NORTHEAST 
FLOW ALOFT WILL MOVE ACROSS NERN CO THRU MIDDAY AND MAY PRODUCE 
PERIODS OF LIGHT SNOW OVER THE PLAINS AT LEAST THRU MIDDAY.  LOW 
LEVEL FLOW ALONG THE FRONT RANGE IS SUPPOSED TO STAY NORTHWEST 
WHICH WOULD KEEP MOST OF THIS LIGHT SNOW EAST OF THE FRONT RANGE 
URBAN CORRIDOR.  HOWEVER AS I WRITE THIS A BAND OF SNOW IS 
INCREASING IN INTENSITY AND MOVING SSW TOWARDS THE FRONT RANGE SO 
THERE IS SOME TYPE OF SURGE COMING IN THAT IS NOT BEING SEEN BY ANY 
OF THE SHORT RANGE MODELS.  THUS MAY HAVE TO INCREASE POPS FROM FORT 
COLLINS SOUTH TO DENVER AT LEAST FOR THE MORNING HOURS.  MEANWHILE 
LOW LEVEL FLOW WILL REMAIN IN THE 40-45 KT RANGE THRU THE AFTN SO 
GUSTY NORTHWEST WINDS OVER THE PLAINS WILL CONTINUE SO WILL EXTEND 
THE BLOWING SNOW ADVISORY THRU MIDDAY FOR THE PLAINS.  IN THE MTNS 
SOME MOISTURE WILL CONTINUE AS WELL WITH WEAK OROGRAPHICS SO WILL 
MENTION A CHC OF -SHSN.  HIGHS TODAY SHOULD BE A FEW DEGREES WARMER 
AS 850-700 MB TEMPS RISE A COUPLE OF DEGREES.   

FOR TONIGHT MOISTURE IS FCST TO LINGER OVER THE PLAINS OVERNIGHT 
HOWEVER CAN NOT SEE ANY FEATURE TO KEEP LIGHT SNOW GOING AFTER 
SUNSET SO WILL ONLY KEEP LOW POPS IN FOR THE EVENING HOURS.  WINDS 
SHOULD SLOWLY DECREASE SO HOPEFULLY BLOWING SNOW WILL BECOME LESS OF 
A PROBLEM BY SUNSET.  

.LONG TERM...MODELS HAVE THE STRONG UPPER CLOSED LOW STILL OVER 
SOUTHERN WISCONSIN 12Z SUNDAY MORNING.  UPPER RIDGING GETS OVER OUR 
FORECAST AREA SUNDAY THROUGH MONDAY NIGHT.  WEAK...MAINLY ZONAL FLOW 
ALOFT IS PROGGED ON SUNDAY.  THE FLOW ALOFT STAYS VERY WEAK SUNDAY 
NIGHT AND MONDAY...WITH WIND DIRECTIONS ALL OVER THE PLACE.  BY 
MONDAY NIGHT IT IS WEST-SOUTHWESTERLY IN DIRECTION AND A BIT 
STRONGER.  THE UPPER SYNOPTIC SCALE PATTERN IS CONVOLUTED SUNDAY 
...WELL INTO THE EXTENDED PERIODS.  THE SYNOPTIC SCALE ENERGY IS 
BENIGN SUNDAY THROUGH MONDAY NIGHT.  THE LOW LEVEL PRESSURE AND WIND 
FIELDS HAVE A PRETTY WEAK GRADIENT OVER THE FORECAST AREA...HOWEVER 
THE FAR EAST IS STILL UNDER NORTHWESTERLY FLOW IN THE BOUNDARY LAYER 
ON SUNDAY WITH THE BIG STORM WELL TO THE EAST.  WEAK LOW LEVEL 
TROUGHING IS PROGGED EAST OF THE MOUNTAINS BY LATE MONDAY AFTERNOON 
AND NIGHT.  NORMAL DIURNAL WIND TRENDS SHOULD DOMINATE.  SUNDAY'S 
MOISTURE IS STILL FAIRLY SIGNIFICANT...ESPECIALLY OVER THE EASTERN 
HALF OF THE PLAINS.  THERE IS STILL QUITE OF BIT OF MID AND UPPER 
LEVEL MOISTURE OVER THE REST OF THE FORECAST AREA AS WELL.  ON 
SUNDAY NIGHT...THERE IS SOME LOW AND MID LEVEL MOISTURE OVER THE 
FORECAST AREA.  MONDAY LOOKS A BIT DRIER...BUT THERE IS STILL SOME 
MOISTURE AROUND.  ON MONDAY NIGHT...THE NAM IS PRETTY DRY...THE GFS 
HAS A LOT OF UPPER LEVEL MOISTURE ONLY.  THE QPF FIELDS OF THE GFS 
SHOW A TAD OF MEASURABLE SNOW OVER THE MOUNTAINS SUNDAY AND SUNDAY 
EVENING...WITH NONE ON THE NAM.  MONDAY AND MONDAY NIGHT SHOW NONE 
ON EITHER MODEL.  FOR POPS...WILL GO WITH 10%S IN THE MOUNTAINS 
SUNDAY...THEN NOTHING THROUGH MONDAY NIGHT.  NO POPS FOR THE PLAINS 
THROUGH THE PERIODS  FOR TEMPERATURES...SUNDAY'S HIGHS ARE 0-1.5 C 
WARMER THAN TODAY'S.  ON MONDAY...HIGHS WARM-UP 1-3 C FROM 
SUNDAY'S.  FOR THE LATER DAYS...MODELS PRETTY MUCH SHOW SPLIT FLOW 
ALOFT FOR THE WESTERN THIRD OF THE UNITED STATES ON TUESDAY.  BY 
WEDNESDAY...THE FORECAST AREA IS MORE UNDER THE INFLUENCE OF WEAK 
UPPER TROUGHING.  THE FLOW ALOFT IS WEAK TUESDAY AND WEDNESDAY.  AN 
UPPER RIDGE IS OVER THE WESTERN UNITED STATES COAST THURSDAY...WITH 
STRONGER NORTHWESTERLY FLOW ALOFT FOR THE FORECAST AREA.  THE GFS 
HAS A JET MAXIMUM MOVE ACROSS THE FORECAST AREA LATE THURSDAY NIGHT 
INTO FRIDAY MORNING.  LATER FRIDAY...THE UPPER RIDGE GETS INTO 
COLORADO AND THE FORECAST AREA...WITH DECREASING ZONAL FLOW ALOFT.  
THERE IS VARIED MOISTURE ACROSS THE FORECAST AREA THROUGH THE FOUR 
DAYS...ALTHOUGH THE MOUNTAINS STAY PRETTY MOIST AND HAVE FAVORABLE 
WEST-NORTHWESTERLY OROGRAPHIC MOUNTAIN TOP FLOW.  WILL GO WITH...OR 
KEEP IN...30% POPS IN THE MOUNTAINS THROUGH THE PERIODS.  THE PLAINS 
LOOK TO BE DRY.  IT APPEARS TEMPERATURES MAY STAY A BIT BELOW THE 
NORMALS. 

&&

.AVIATION...BAND OF SNOW LOOKS LIKE IT WILL AFFECT THE AIRPORT FROM 
10Z-12Z WITH ACCUMULATIONS UP TO ONE HALF INCH POSSIBLE.  THE REST 
OF THE DAY WILL DEPEND ON LOW LEVEL FLOW.  MODELS KEEP FLOW NW 
HOWEVER IT REMAINS TO BE SEEN WHETHER THIS WILL BE THE CASE OR NOT.  
FOR NOW WILL BELIEVE THEM AND ONLY MENTION A SLIGHT CHC OF -SHSN FOR 
THE AFTN HOURS AND KEEP WINDS NNW WITH SPEEDS IN THE 10-15 MPH 
RANGE.  CEILINGS WILL STAY IN THE 5000-6000 FEET RANGE HOWEVER THEY 
MAY DROP TO 1500-2000 IN LOCAL SNOW SHOWERS WITH VISBILITIES IN THE 
1-3 MILE RANGE FOR A BRIEF PERIOD OF TIME.  FOR TONIGHT DO NOT 
EXPECT ANY PCPN WITH CEILINGS IN THE 6000-7000 FT RANGE WITH WINDS 
BECOMING DRAINAGE AFTER 03Z.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...WINTER WEATHER ADVISORY FOR THE   
      NORTHEAST COLORADO PLAINS UNTIL NOON TODAY...ZONES             
      42..44..45..46..48..49..50..51.

$$

RPK/RJK