FXUS65 KBOU 120328
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER CO
830 PM MST FRI DEC 11 2009

.SHORT TERM...EVENING UPDATE...ZONES HAVE BEEN AMENDED FOR COLDER 
TEMPS THAN EXPECTED IN THE SOUTH PLATTE RIVER VALLEY...AND CLOUDS 
HAVE BEEN SLOW TO ARRIVE IN THE NORTHERN MOUNTAIN VALLEYS SO 
KREMMLING WAS FALLING FAST.  I THINK KREMMLING WILL REACH THEIR MIN 
BY MIDNIGHT THEN INCREASING CLOUDS WILL LIMIT ANY ADDITION COOLING.  

THROUGH SATURDAY...INCREASED CIRCULATION ASSOCIATED WITH THE PASSING 
SHORT WAVE WILL HELP FURTHER ERODE THE COLD AIR ON THE PLAINS.  
CROSS SECTIONS INDICATE THE WESTERLY WINDS WILL MOVE AWAY FROM THE 
FOOTHILLS A LITTLE BIT ON SATURDAY...BUT WITH THE MAGNITUDE OF THE 
WINDS DOWN A LITTLE BIT...DO NOT SEE A HIGH WIND THREAT.  FOR THE 
TIME BEING...A SLIGHT CHANCE OF SNOW IN THE HIGH MOUNTAINS IS THE 
ONLY THREAT OF PRECIPITATION FOR NOW.  HEAVIER PRECIPITATION IS NOT 
EXPECTED UNTIL LATER TOMORROW NIGHT.      

.LONG TERM...MOISTURE ASSOCIATED WITH WEAK TROUGH MOVING ONTO THE 
WEST COAST THIS AFTERNOON SHOULD CONTINUE TO GRADUALLY INCREASE 
ACROSS THE MOUNTAINS SATURDAY EVENING.  HOWEVER...OROGRAPHIC FLOW IS 
NOT FAVORABLE WITH SOUTHWEST MOUNTAIN TOP WINDS SO ANY ACCUMULATION 
WILL BE LIGHT.  BY SUNDAY...A MORE SIGNIFICANT SHORT WAVE WILL MOVE 
ACROSS THE STATE PER THE Q-G VERTICAL MOTION FIELDS.  THIS...ALONG 
WITH COLD ADVECTION AND MID LEVEL FLOW TURNING MORE WESTERLY...WILL 
RESULT IN MORE WIDESPREAD SNOWFALL AND A FEW INCHES OF 
ACCUMULATION.  RHEA-THALER SNOW MODEL SUGGESTS ACCUMULATIONS OF 2-6 
INCHES POSSIBLE ACROSS THE FRONT RANGE MOUNTAINS...AND A COUPLE MORE 
THAN THAT IN THE RABBIT EARS PASS AREA.  BY MONDAY...SNOW SHOULD 
DECREASE AS AIRMASS BEGINS TO DRY OUT AND BECOMES MORE SUBSIDENT.

PERIODS OF GUSTY WINDS CAN ALSO BE EXPECTED IN/NEAR THE FRONT RANGE 
MOUNTAINS AND FOOTHILLS THROUGH MONDAY.  THE STRONGEST WINDS APPEAR 
TO BE SHAPING UP FOR SUNDAY AS CROSS MOUNTAIN FLOW INCREASES TO 
AROUND 40 KNOTS.  HOWEVER...STABLE LAYER IS VIRTUALLY NON-EXISTENT 
SO SEE LITTLE MOUNTAIN WAVE AMPLIFICATION BUT A FEW GUSTS IN EXCESS 
OF 50 MPH POSSIBLE IN WIND PRONE AREAS.  BY SUNDAY NIGHT AND 
MONDAY...THE STABLE LAYER WILL LOWER BUT BY THAT TIME THE CROSS 
MOUNTAIN FLOW IS WEAKENING SO SEE LITTLE THREAT OF ANY HIGH WINDS AT 
THIS TIME.

TEMPERATURES WILL BE ABOVE NORMAL THROUGH SUNDAY WITH BETTER 
DOWNSLOPE FLOW AND COLD ADVECTION NOT KICKING IN UNTIL LATE IN THE 
DAY.  THE MORE CONCERNING PORTION OF THE TEMPERATURE FORECAST 
REVOLVES AROUND ANOTHER MASS OF ARCTIC AIR NOW RESIDING IN NORTHERN 
ALBERTA AND SASKATCHEWAN WHERE CURRENT TEMPS ARE IN THE 30S BELOW 
ZERO.  THIS VERY COLD AND DENSE AIRMASS WILL BE HARD TO KEEP FROM 
SLOSHING BACK INTO EASTERN COLORADO...ESPECIALLY WITH ALL THE SNOW 
COVER TO THE NORTH AND EAST OF US AND ANOTHER FAST MOVING SHORT WAVE 
ACROSS THE NORTHERN BORDER.  IF THE COLD AIR MANAGES TO STAY OUT ON 
MONDAY...THEN THIS NEXT PASSING SHORT WAVE SHOULD GIVE ANOTHER PUSH 
TO THE COLD AIR MONDAY NIGHT AND ALLOW IT TO MOVE IN.  HAVE NUDGED 
TEMPERATURES DOWN A FEW DEGREES...BUT WILL DEFINITELY HAVE TO WATCH 
POTENTIAL FOR THIS ARCTIC INTRUSION.

BY THE MIDDLE OF NEXT WEEK...A DRY AND WARMER AIRMASS WILL SPREAD 
ACROSS THE FORECAST AREA AS WEAK RIDGING BUILDS OVER THE ROCKIES.  
THIS SHOULD ALLOW A RETURN TO ABOVE NORMAL TEMPERATURES FOR NEXT
WEDNESDAY THROUGH FRIDAY.

&&

.AVIATION...NO AVIATION IMPACTS THRU THE NEXT 24 HOURS BUT HIGH CIGS 
WILL BECOME BKN-OVC AT TIMES.  ELY-SELY SFC WINDS LATE THIS AFTN 
SHOULD BECOME DRAINAGE AS THE SUN GOES DOWN.  COLD AIR SHOULD 
CONTINUE ERODING ON SATURDAY AS WESTERLY FLOW ALOFT CONTINUES.  
BREEZY DOWNSLOPE WINDS ALONG THE FOOTHILLS ON SATURDAY ARE NOT 
EXPECTED TO SPREAD FAR ENOUGH EASTWARD TO IMPACT AIRPORT 
OPERATIONS.  

&&

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

$$

KDRBY/BARJENBRUCH