FXUS65 KBOU 262135
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER CO
230 PM MST THU NOV 26 2009

.SHORT TERM...VERY WEAK BOUNDARY LAYER FLOW IS OVER MUCH OF THE 
FORECAST AREA CURRENTLY.  STRONGER NORTHWESTERLY WINDS ARE INDICATED 
RIGHT ON THE DIVIDE.  THERE ARE A FEW HIGH CLOUDS EMBEDDED IN THE 
NORTHWESTERLY FLOW ALOFT PUSHING SOUTHEASTWARD OVER THE FORECAST 
AREA.  MODELS HAVE THE UPPER RIDGE AXIS MOVE ACROSS COLORADO TONIGHT 
INTO EARLY FRIDAY.  THE FLOW ALOFT WILL BE WEAK WEST-NORTHWESTERLY 
FOR THE FORECAST AREA TONIGHT AND FRIDAY.  THE SYNOPTIC SCALE ENERGY 
IS PROGGED TO BE BENIGN TONIGHT AND FRIDAY.  THE BOUNDARY LAYER 
WINDS ARE PROGGED TO CONTINUE LIGHT WITH A WEAK GRADIENT INDICATED 
THROUGH FRIDAY.  BOTH MODELS HAVE VERY LITTLE MOISTURE AT ANY LEVEL 
PROGGED FOR THE FORECAST AREA THROUGH FRIDAY.  NO POPS.  FOR 
TEMPERATURES...FRIDAY'S HIGHS LOOK 0-1 C WARMER THAN THIS 
AFTERNOON'S.  

.LONG TERM...VERY DRY AIR WILL BE IN PLACE FRIDAY NIGHT WITH ONLY A 
SLIGHT INCREASE ON SATURDAY AS THE RIDGE AXIS MOVES EAST. PERHAPS 
SOME CLOUD COVER...BUT SHOULD BE TOO DRY FOR PRECIPITATION DESPITE 
SOME WEAK LIFT. MODELS ARE PRETTY CONSISTENT WITH A SPLIT TROUGH 
MOVING OVER COLORADO SATURDAY NIGHT AND SUNDAY. NAM AND ECMWF HAVE 
ENOUGH SHARPNESS IN THE SOUTHERN PART OF THE TROUGH TO PRODUCE A 
DEFORMATION BAND WITH SNOW...12Z NAM GAVE A 6 INCH SNOW BAND OVER 
THE PALMER DIVIDE...LATEST RUN HAS THIS FURTHER SOUTH. GFS HAS LESS 
OF THIS AND THE MAIN FEATURE IS THE NORTHERN PART OF THE WAVE THAT 
GIVES A MORE WIDESPREAD BUT LIGHTER SNOWFALL. SREF MEMBERS HAD BEEN 
AVERAGING AROUND 4 INCHES OF SNOW FOR DENVER...BUT THIS MORNINGS 
ENSEMBLE BACKED OFF TO 1 TO 2 INCHES. TOO EARLY TO FOCUS ON DETAILS 
BUT I DID CONTINUE TO FAVOR THE SOUTHERN PART OF THE AREA THAT WILL 
BE MORE LIKELY TO HAVE SIGNIFICANT LIFT. RAISED POPS GENERALLY WITH 
HIGHER CONFIDENCE IN AT LEAST A LITTLE SNOWFALL. ALSO LOWERED TEMPS 
ON SUNDAY.

FOR THE LATER PERIODS...A GOOD BREAK ON MONDAY AND TUESDAY BUT 
WARMUP IS PROBLEMATIC. WESTERLY FLOW BREAKS OUT OF THE NORTHERN 
ROCKIES AND SPREADS WARM AIR ONTO THE PLAINS...BUT DIFFERENCES IN 
THE TIMING OF THIS SPREADING SOUTH. ALSO HARD TO KNOW IF THIS WILL 
SCOUR OUT THE COLD AIR OR PRODUCE A LEE TROUGH LIMITING THE WARMTH 
TO NEAR THE MOUNTAINS. IF THERE IS DECENT SNOW COVER FROM SUNDAY 
THIS WILL ALSO INHIBIT THE MIXING. FOR NOW WILL PLAY THE COOLEST 
AREAS IN THE SOUTH PLATTE VALLEY WITH BETTER WARMUP ALONG THE 
FOOTHILLS AND SOME HEDGING IN THE NORTHEAST CORNER.

DECENT AGREEMENT ALSO ON A LONGWAVE TROUGH DEVELOPING OVER THE 
CENTRAL U.S. BY WEDNESDAY. STILL SOME QUESTION ABOUT THE WESTWARD 
EXTENT OF THE TROUGH AXIS...00Z ECMWF HAS US IN THE COLDEST AIR FOR 
A LONG TIME WHILE THE GFS HAS TRIED TO KEEP US ON THE EDGE. NOT SUCH 
A BIG DIFFERENCE FOR WEDNESDAY AND THURSDAY...MORE A MATTER OF HOW 
LONG IT LASTS AND WHETHER IT GET REINFORCED WITH ADDITIONAL 
SHORTWAVES. NOT TREMENDOUSLY COLD AS THERE IS NOT A SUPER COLD POOL 
ESTABLISHED AND NO SNOW COVER UPSTREAM EITHER...BUT WE COULD GET 
DOWN TO AROUND ZERO IF IT CLEARS OUT AND HIGHS BELOW FREEZING LOOK 
LIKE A GOOD POSSIBLITY. FOR NOW WE WILL HAVE TEMPERATURES NEAR THE 
COLD END OF THE GFS ENSEMBLE RANGE. THIS PATTERN IS NOT TOO GOOD FOR 
SIGNIFICANT SNOWFALL...BUT COULD PRODUCE SOME LITTLE SNOWS. WE WILL 
PROBABLY NEED HIGHER POPS SOMEWHERE IN THE LAST COUPLE DAYS OF THE 
FORECAST...BUT STILL PLENTY OF UNCERTAINTY ABOUT TIMING.

&&

.AVIATION...CLEAR SKIES WILL CONTINUE OVER THE AIRPORT...WITH 
PERHAPS A FEW HIGH CLOUDS TONIGHT AND FRIDAY.  FAIRLY WEAK NORMAL 
DIURNAL WINDS TRENDS WILL PREVAIL.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...NONE. 

$$
RJK/GIMMESTAD