Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 211625
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
925 AM MST SUN DEC 21 2014

.UPDATE...
ISSUED AT 925 AM MST SUN DEC 21 2014

SATELLITE IMAGERY SHOWING SNOW MAKING ITS WAY INTO WESTERN
COLORADO AS THE POOL OF MOISTURE AND JET MOVES SOUTHEAST. WILL
NOT MAKE ANY UPDATES TO THE ON-GOING WARNING PRODUCTS AS TIMING
AND SNOW FALL AMOUNTS ARE STILL ON TRACK...HOWEVER HAVE DECIDED TO
HOLD OFF ON ANY POSSIBLE BLIZZARD WARNINGS AS THE VALLEYS WILL
MOST LIKELY NOT BE HIT WITH THE HIGHEST WIND GUSTS. MODEL CROSS
SECTIONS ARE STILL INDICATING MOST OF THE HIGHER WINDS WILL BE
REGULATED TO THE HIGHER MOUNTAIN PASSES AND ABOVE TIMBERLINE WITH
GUSTS TO 60 TO 70 MPH BETWEEN 4 AND 8 PM THIS EVENING. THIS WILL
CREATE EXTREMELY HAZARDOUS DRIVING CONDITIONS FOR TRAVELERS ON
I-70 THIS EVENING WITH GREATLY REDUCEDED VISIBILITIES. PUSHING
THE EFFECTS OF THE HEAVY SNOW AT THIS TIME IN ADDITION TO THE
INCREASED WINDS OVER WELL TRAVELED PASSES THROUGH CONFERENCE CALLS
AND ON SOCIAL MEDIA. WILL RE-ASSESS THE BLIZZARD WARNING THIS
AFTERNOON BASED ON UPSTREAM OBS OVER NW COLORADO.

&&

.SHORT TERM...(TODAY THROUGH TONIGHT )
ISSUED AT 523 AM MST SUN DEC 21 2014

MOISTURE PLUME MOVING INTO COLORADO THIS MORNING ON THE NOSE OF A
VERY STRONG JET. FOR THIS MORNING THERE IS WEAK WARM ADVECTION AND
INCREASING WINDS...WITH DEEPENING MOISTURE BUT WITH SOME MID LEVEL
STABILITY. THIS SHOULD GENERATE STEADY SNOW OVER AND WEST OF THE
FRONT RANGE...BUT NOT HEAVY YET. THIS AFTERNOON THE LIFT WILL
INCREASE A BIT AND COLD ADVECTION WILL SET IN MAKING FOR A MUCH
MORE PRODUCTIVE ENVIRONMENT THIS EVENING. IT LOOKS LIKE THE BEST
LIFT...STRONGEST WINDS...AND BEST INSTABILITY WILL BE OVER THE
INTERSTATE 70 CORRIDOR IN THE LATE AFTERNOON AND EVENING. BAD
TIMING FOR TRAFFIC...SO THE IMPACT COULD BE SUBSTANTIAL. WE WILL
BE HITTING THIS MESSAGE HARD TODAY. WINDS GO MORE NORTHERLY LATER
TONIGHT WITH THE BEST LIFT SINKING SOUTH...BUT STILL REASONABLY
GOOD CONDITIONS FOR MODERATE TO HEAVY SNOW THE REST OF THE NIGHT.
CURRENT HIGHLIGHTS LOOK ALRIGHT...TWEAKED THE TIMING OF THE SNOW A
BIT TO HIT THIS EVENING THE HARDEST. THIS MAY BE A CANDIDATE FOR A
BLIZZARD WARNING LATER TODAY IF IT PANS OUT.

FOR AREAS EAST OF THE DIVIDE...DOWNSLOPE WINDS BUT PLENTY OF SNOW
SPILLING OVER INTO THE FOOTHILLS. IN ADDITION SOME FORCING WITH
THE JET SO WE WILL NEED SOME ACCUMULATIONS IN THE HIGHER FOOTHILLS
AND SOUTH PARK AT THE HEIGHT OF THE EVENT. SOME THREAT OF HIGH
WINDS...THOUGH NOT ENOUGH FOR A WARNING. HIGH WINDS APPEAR LIKELY
FOR THE HIGHER MOUNTAIN AREAS THAT ARE IN THE WINTER STORM
WARNING...SUCH AS BERTHOUD PASS...NIWOT RIDGE AND OTHER ABOVE
TIMBERLINE AREAS STICKING UP INTO THE JET. FOR THE MORE POPULATED
FOOTHILL AREAS GUSTS IN THE 50-70 MPH RANGE LOOK LIKELY TONIGHT.
JET RELATED BANDING MAY BE STRONG ENOUGH TO OVERCOME THE DOWNSLOPE
AT SOME POINT...ESPECIALLY LATER TONIGHT AS THE DEEP WIND
COMPONENT BECOMES MORE NORTHERLY AND THERE COULD BE SOME LOW LEVEL
CONVERGENCE SOMEWHERE ON THE EAST SIDE. PROBABLY A BETTER CHANCE
FURTHER AWAY FROM THE MOUNTAINS...BUT SOME THREAT IN DENVER AS
WELL. THIS STUFF WILL PROBABLY BE LIGHT BUT WITH THE STRENGTH OF
THE JET AND SOME INSTABILITY THERE COULD BE SOME PLACES THAT GET A
COUPLE OF INCHES AS A SHOWER BAND COMES OVER.

BOOSTED HIGH TEMPERATURES A COUPLE OF DEGREES TODAY...WARM AIRMASS
AND WINDY.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 523 AM MST SUN DEC 21 2014

THERE IS NORTHWESTERLY FLOW ALOFT FOR THE FORECAST AREA ON MONDAY.
THE FLOW ALOFT BECOMES ALMOST DUE NORTHERLY BY 12Z TUESDAY MORNING
WITH JET LEVEL SPEEDS ON THE INCREASE. THE FLOW ALOFT IS NORTHERLY
AROUND 100 KNOTS TUESDAY AND TUESDAY NIGHT. DOWNWARD SYNOPTIC
SCALE ENERGY IS PROGGED OVER THE CWA ALL FOUR PERIODS...MONDAY
THROUGH TUESDAY NIGHT. THE BOUNDARY LAYER FLOW IS ALL NORTHWESTERLY
FOR THE CWA MONDAY THROUGH TUESDAY. CONCERNING MOISTURE...IT STAYS
FAIRLY DEEP OVER THE MOUNTAINS MONDAY AND MONDAY NIGHT. BY TUESDAY
...MOISTURE IS DECREASING IN THE HIGH COUNTRY. BUT NOT TOTALLY
GONE UNTIL TUESDAY EVENING. FOR THE PLAINS...IT IS PRETTY DRY
MONDAY MORNING...THEN MOISTURE INCREASES IN THE MID AND UPPER
LEVELS...LOWERING...ESPECIALLY OVER THE EASTERN HALF BY MONDAY
EVENING CONTINUING INTO TUESDAY. ALL AREAS ARE PRETTY DRY TUESDAY
NIGHT. THE QPF FIELDS HAVE PRETTY DECENT AMOUNTS PROGGED IN THE
MOUNTAINS MONDAY...DECREASING MONDAY NIGHT. THERE IS LITTLE TO NO
MEASURABLE PRECIPITATION PROGGED FOR THE PLAINS MONDAY...BUT A TAD
FOR MONDAY NIGHT INTO TUESDAY MORNING. SO FOR POPS...THE
HIGHLIGHTS ARE OUT AND WE ARE EXPECTING A HEALTHY SNOWFALL FOR
THE MOUNTAINS. WIDESPREAD SNOW AND SOME BLOWING SNOW TOO ARE
EXPECTED IN THE MOUNTAINS MONDAY INTO MONDAY EVENING BEFORE
DECREASING INTO TUESDAY. PLAINS POPS WILL BE 0-30%S MONDAY INTO
MIDDAY TUESDAY. TEMPERATURES ON MONDAY ARE PROGGED TO BE 6-10 C
COLDER THAN TODAY`S HIGHS. TUESDAY IS ANOTHER 1-4 C COOLER THAN
MONDAY FOR HIGHS. FOR THE LATER DAYS...WEDNESDAY THROUGH SATURDAY
...MODELS HAVE STRONG NORTHERLY FLOW ALOFT ON WEDNESDAY WITH UPPER
RIDGING TO MOVE OVER THE CWA THROUGH WEDNESDAY NIGHT. THEN A
BROAD UPPER TROUGH MOVES IN THURSDAY INTO FRIDAY NIGHT. THE FLOW
ALOFT IS WEST-NORTHWESTERLY AND MODERATE IN SPEED. ON SATURDAY
STRONG NORTH-NORTHWESTERLY FLOW ALOFT IS PROGGED. THE ECMWF HAS
BETTER PARAMETERS OVERALL FOR SNOW THURSDAY INTO FRIDAY...
ESPECIALLY IN THE MOUNTAINS.

&&

.AVIATION...(FOR THE TAFS THROUGH 18Z MONDAY MORNING)
ISSUED AT 925 AM MST SUN DEC 21 2014

VFR CONDITIONS WILL PREVAIL FOR THE MORNING AND AFTERNOON TIME
PERIODS TODAY. WINDS WILL INCREASE THIS AFTERNOON WITH POSSIBLE
GUSTS UP TO 25 MPH INCREASING AROUND 03Z MONDAY TO 30 MPH. AFTER
03Z CEILINGS MAY DROP BELOW 6000 FT WITH LIGHT SNOW POSSIBLE. SNOW
IS NOT EXPECTED TO BE HEAVY ENOUGH TO REDUCE VISIBILITIES BELOW A
MILE BUT SOME REDUCTION IN VIS WILL BE POSSIBE AROUND 09Z WHEN
MODELS INDICATE THE HEAVIEST SNOW COULD BE.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM NOON TODAY TO MIDNIGHT MST MONDAY
NIGHT FOR COZ031>034.

WINTER WEATHER ADVISORY FROM NOON TODAY TO MIDNIGHT MST MONDAY
NIGHT FOR COZ030.

&&

$$

UPDATE...BOWEN
SHORT TERM...GIMMESTAD
LONG TERM...RJK
AVIATION...BOWEN


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