FXUS65 KBOU 272203
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER CO
303 PM MST FRI NOV 27 2009

.SHORT TERM...SATELLITE PICTURES SHOW A BIT OF HIGH CLOUDINESS OVER 
SOME OF THE FORECAST AREA THIS TIME.  THERE IS PLENTY OF CLOUDS TO 
OUR WEST AND NORTH.  MODELS HAVE GRADUALLY INCREASING WESTERLY 
...THEN SOUTHWESTERLY FLOW ALOFT TONIGHT INTO SATURDAY.  THE QG 
VERTICAL VELOCITY FIELDS HAVE WEAK UPWARD MOTION PROGGED TONIGHT AND 
SATURDAY.  THE BOUNDARY LAYER WINDS WILL BE NORMAL DIURNAL 
TONIGHT...BUT ON SATURDAY...MODELS HAVE A SURGE AND SOME UPSLOPE 
MOVE IN BETWEEN 15Z AND 18Z IN THE MORNING.  THIS UPSLOPE CONTINUE 
THROUGH SATURDAY AFTERNOON.  FOR MOISTURE...MOST LEVELS CONTINUE 
VERY DRY OVERNIGHT ON BOTH MODELS...WITH AN INCREASE OF HIGH LEVEL 
CLOUDINESS AFTER MIDNIGHT.  IT STAYS DRY IN THE LOWER AND MID LEVELS 
THROUGH 18Z ON BOTH MODELS.  MOISTURE LOWERS AND DEEPENS SOMEWHAT 
SATURDAY AFTERNOON IN MOST AREAS...EXCEPT OVER THE MOUNTAINS ON 
NAM.  THERE IS NO QPF OVER THE FORECAST AREA ON EITHER MODEL THROUGH 
00Z SATURDAY AFTERNOON LATE.  FOR POPS...WILL START SOME MINIMAL 
POPS IN THE HIGH MOUNTAINS ABOUT MID SATURDAY AFTERNOON...THAT'S 
IT...OTHERWISE DRY FOR THE REST OF THE ZONES.  FOR SATURDAY'S HIGH 
TEMPERATURES...THICKNESS GRIDS SHOW READINGS ABOUT 6-11 C COLDER 
THAN THIS AFTERNOON'S HIGHS.      

.LONG TERM...A SPLITTING UPPER TROUGH WILL MOVE ACROSS THE AREA 
SATURDAY NIGHT AND SUNDAY. QG FORCING WITH THIS IS VERY WEAK AS THE 
LIFT ASSOCIATED WITH THE SOUTHERN PART OF THE TROUGH SHOULD STAY 
SOUTH OF OUR AREA. STILL...THERE WILL BE A BAND OF MOISTURE AND 
SLIGHT INSTABILITY ASSOCIATED WITH THE COOLING AND A BRIEF SURGE OF 
NORTH WINDS SATURDAY NIGHT. NAM/GFS HAVE CONSISTENTLY SHOWN 
WIDESPREAD LIGHT SNOW...BUT AN INCH OR LESS ON THE PLAINS WITH A 
LITTLE MORE IN THE MOUNTAINS. GIVEN THAT WE ARE CLEARLY ON THE 
NORTHERN SIDE OF THE SPLITTING...WE SHOULD SEE A BAND THAT CONTINUES 
TO MOVE ACROSS WITH ONLY A BIT OF SLOWING AS IT PASSES SOUTH. MAIN 
CHANGE THIS PACKAGE WAS TO SPEED UP THE DEPARTURE OF THE SYSTEM LATE 
SUNDAY. BETWEEN A BETTER CHANCE OF SUN AND LESS CHANCE OF DECENT 
SNOW COVER...I RAISED HIGH TEMPS A BIT SUNDAY AND MONDAY. MONDAY AND 
TUESDAY LOOK SUNNY...THOUGH IT DOES NOT LOOK LIKE THERE WILL BE MUCH 
WIND. PROBABLY NOT MUCH SNOW COVER TO WORRY ABOUT...BUT THE 
INVERSION WILL NONETHELESS BE DIFFICULT TO BREAK WITHOUT THE WIND. I 
WARMED THESE DAYS UP A BIT MORE...BUT NOWHERE NEAR WHAT THE 
TEMPERATURES ALOFT WOULD SUPPORT WITH BETTER MIXING.

LATER PERIODS REMAIN TROUBLESOME. THERE HAS BEEN A DECENT CONSENSUS 
ON A COLD TROUGH DIGGING INTO THE MIDDLE OF THE COUNTRY...FAR ENOUGH 
WEST TO GET US STUCK IN THE COLD AIR.  HOWEVER THE LATEST ECMWF RUNS 
HAVE BACKED OFF ON THE WESTWARD EXTENT A BIT...AND THE GFS HAS BEEN 
STUBBORNLY OUTSIDE OF THIS CONSENSUS WITH A PROGRESSIVE LOWER 
AMPLITUDE FLOW FOR THE PAST SEVERAL RUNS. YESTERDAYS FORECAST OF 
TEMPERATURES DROPPING TO AROUND 30 FOR HIGHS FROM WEDNESDAY ON WAS 
IN THE MIDDLE OF THE ENVELOPE YESTERDAY...NOW IT MAY BE MORE ON THE 
COLD SIDE BUT STILL LOOKS LIKE A DECENT POSSIBILITY. A SHALLOW 
TROUGH COULD MEAN A FASTER RECOVERY...HOWEVER THE GFS SOLUTION 
ACTUALLY RESULTS IN THE COLDER AIR DRIFTING IN FROM THE EAST ABOUT 
FRIDAY. LACKING ANY BETTER DIRECTION WE WILL STICK WITH THE CURRENT 
FORECAST. STILL A DECENT CHANCE FOR SNOW IN THERE SOMEWHERE...THOUGH 
IN THAT PATTERN IT SHOULD BE LIGHT. LOW POPS IN ORDER UNTIL THERE IS 
BETTER DEFINITION.
&&

.AVIATION...JUST A FEW HIGHS CLOUDS ARE EXPECTED OVER THE AIRPORT 
TONIGHT THROUGH SATURDAY MORNING.  A COLD FRONT AND NORTH-NORTHEAST
UPSLOPE WINDS MOVE IN IN FROM 15Z-18Z SATURDAY.  BY 21Z SATURDAY 
AFTERNOON...A STRATUS CEILING IS LIKELY TO DEVELOP AROUND 2000-3000 
FEET AGL.  PRECIPITATION IS NOT EXPECTED UNTIL AFTER 00Z SATURDAY 
EVENING.
&&

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

$$
RJK/GIMMESTAD