Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 240320
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
820 PM MST TUE DEC 23 2014

.UPDATE...
ISSUED AT 820 PM MST TUE DEC 23 2014

FOR TONIGHT...NOTHING TO CHANGE IN THE FIRST PART OF THE
FORECAST. SKIES HAVE CLEARED OUT THIS EVENING AND WINDS HAVE
DIMINISHED. SURFACE PRESSURE GRADIENTS ACROSS EASTERN COLORADO
WILL BE RELAXING OVERNIGHT ALLOWING WINDS TO DROP TO NEAR CALM OR
TOWARDS TYPICAL DRAINAGE PATTERNS. DRIER AIR CONTINUES MOVING IN
FROM THE NORTH AS TEMPERATURES ALSO TUMBLE. LOW LEVELS SHOULD BE
TOO DRY AND TOO COLD FOR ANY LOW CLOUDS OR FOG TO DEVELOP.

FOR THURSDAY AFTERNOON AND EVENING...NEW NAM KEPT THE SAME TREND
OF SNOW ADVANCING ACROSS THE PLAINS BETWEEN 18Z AND 06Z GIVEN THE
HIGH TRAVEL DEMANDS ON CHRISTMAS IT BECAME APPARENT THAT WE NEEDED
TO SHOW SOME THREAT OF SNOW DURING THE AFTERNOON. DIVIDED THE 6
HOUR PERIOD THURSDAY AFTERNOON... WITH NO CHANGE TO PREVIOUS
FORECAST FROM 18Z TO 21Z...AND SHOW THE TRANSITION TO SCATTERED
SNOW FOR THE PLAINS AS THE SYSTEM MOVES IN. THE SNOW QPF FORECAST
LOOKED REASONABLE FOR THURSDAY NIGHT...RAISED POPS TO DEFINITE
SINCE WE ARE SHOWING MEASURABLE SNOW. LATER SHIFTS CAN LOOK AT
WHETHER THIS SYSTEM WILL LINGER LONGER INTO FRIDAY. BOTTOM LINE IS
WE WILL HAVE A WHITE CHRISTMAS FOR MOST OF THE FORECAST AREA.

&&

.SHORT TERM...(THIS AFTERNOON THROUGH WEDNESDAY)
ISSUED AT 304 PM MST TUE DEC 23 2014

STRONG WINDS AND BLOWING SNOW WILL CONTINUE TO DECREASE THROUGH THE
LATE AFTERNOON AND EARLY EVENING HOURS OVER THE EASTERN PLAINS. MAY
SEE A FEW FLURRIES THROUGH 6 PM...BUT NO ACCUMULATION IS EXPECTED.

AN UPPER LEVEL RIDGE BUILDING OVER REGION WILL CAUSE NORTHERLY FLOW
ALOFT TO TURN NORTHWESTERLY AND DRY. SKIES WILL CLEAR TONIGHT AND
EXPECT MOSTLY SUNNY TO PARTLY CLOUDY SKIES FOR WEDNESDAY.
TEMPERATURES WILL BE WARMER UNDER THIS RIDGE WITH HIGHS IN THE 40S
ALONG THE FRONT RANGE. MAY SEE HIGH CLOUDS INCREASE LATE WEDNESDAY
AFTERNOON OVER THE MOUNTAINS AS PACIFIC MOISTURE INCREASE AT THE
UPPER LEVELS.

.LONG TERM...(WEDNESDAY NIGHT THROUGH MONDAY)
ISSUED AT 304 PM MST TUE DEC 23 2014

MILD...BREEZY AND DRY CONDITIONS DOMINATE WEDNESDAY NIGHT AHEAD
OF A DEEPENING UPPER LEVEL TROUGH ADVANCING ACROSS NEVADA AND
UTAH. CONFIDENCE IN THE CHRISTMAS DAY AND NIGHT FORECASTS
CONTINUE TO IMPROVE AS MODELS OVER THE PAST 24 HOURS HAVE
CONVERGED OF A SIMILAR SOLUTION. AS THE UPPER TROUGH NEARS
WESTERN COLORADO...ISENTROPIC UPGLIDE AND DEEP LAYER MOISTURE
INCREASE OVER THE HIGH COUNTRY. COULD SEE SCATTERED SNOW SHOWERS
FORMING OVER HIGHER ELEVATIONS OF THE NORTH CENTRAL BY LATE
MORNING OR EARLY AFTERNOON AS LAPSE RATES STEEPEN TOGETHER WITH A
FEW RAIN/SNOW SHOWERS OVER THE LOWER MTN VALLEYS. SWLY FLOW AT MTN
TOP LEVEL NOT ALL THAT STRONG SO OROGRAPHICS NOT CONTRIBUTING
MUCH INITIALLY TO PRECIP DEVELOPMENT. EAST OF THE MTNS...CHRISTMAS
DAY APPEARS TO START OUT DRY AND RELATIVELY MILD WITH LIGHT SOUTH-
SOUTHWESTERLY LOW-LEVEL FLOW WITH PRESSURE FALLS TO OUR NORTHEAST
JUST AHEAD OF A COLD FRONT STRETCHED ACROSS SERN WYOMING/WRN
NEBRASKA. MODELS GENERALLY AGREE IN DROPPING THIS FRONTAL BNDRY
SOUTH ACRS NERN COLORADO MID TO LATE MORNING WITH LIGHT NELY
BNDRY LAYER WINDS IN THE DENVER AREA BY MIDDAY. NOT MUCH IN THE
WAY OF LOW LEVEL MOISTURE IMMEDIATELY BEHIND THE FRONT SO ONLY A
GRADUAL INCREASE IN CLOUDS THROUGH THE AFTERNOON AND A TOP OFF IN
TEMPERATURES NOT LONG AFTER MIDDAY. ALTHOUGH WITH THE UPPER TROUGH
NEARING...EXPECT TO SEE SCATTERED RAIN/SNOW SHOWERS FORMING UP
ALONG THE WY/NE BORDER DURING THE AFTERNOON.

BY THURSDAY NIGHT...UPPER TROUGH DYNAMICS AND COLD AIR PASSES
OVERHEAD. NELY UPSLOPE FLOW DEEPENS EAST OF THE MTNS AND SFC-650
MB LAYER SATURATES. TEMPERATURES ON THE PLAINS FALL BELOW
FREEZING BY EVENING AND ANY PRECIP SHOULD BE SNOW. OVERALL MODELS
INDICATE WIDESPREAD 1-2 INCH SNOW ACCUMULATIONS ON THE PLAINS
OVERNIGHT...WITH AREAS OF 3-5 INCH AMOUNTS IN AND ALONG THE FRONT
RANGE AND OVER THE PALMER DIVIDE. MANY MTN AREAS COULD RECEIVE
SIMILAR OR SLIGHTLY GREATER AMOUNTS BY FRIDAY MORNING. STILL TOO
EARLY TO KNOW FOR SURE EXACTLY WHERE THESE AMOUNTS WILL FALL...BUT
A WHITE CHRISTMAS NIGHT LOOKS LIKE A GOOD BET FOR MOST OF THE FCST
AREA.

FOR FRIDAY...MODELS STILL SHOW THE UPPER TROUGH OVER THE REGION.
LOOKING FOR PLENTY OF CLOUDS AND BLUSTERY NORTHERLY WINDS THROUGH
THE DAY...WITH LINGERING LIGHT SNOWFALL ALONG THE FOOTHILLS AND
PALMER DIVIDE ENDING BY AROUND MIDDAY. MOUNTAINS SHOULD ALSO SEE A
DROP OFF IN SNOWFALL DURING THE AFTERNOON WITH DRIER AIR SWINGING
DOWN OF THE BACK SIDE THE EXITING UPPER TROUGH. ANY ADDITIONAL
SNOW ACCUMULATION ON FRIDAY SHOULD BE MINOR. IN NOW APPEARS THAT
FRIDAY WILL END UP BEING THE COLDEST DAY OF THE WEEK. MAY STRUGGLE
TO CLIMB OUT OF THE 20S IN ALL AREAS ON FRIDAY.

FOR THE WEEKEND...LATEST 12Z GFS AND EC MODEL RUNS SHOW YET
ANOTHER UPPER TROUGH AND POOL OF COLD AIR ALOFT DROPPING DOWN
ACROSS NORTHERN COLORADO ON SATURDAY. COULD SEE ANOTHER ROUND OF
LIGHT SNOW IN THE HIGH COUNTRY AND A SLIGHT CHANCE OF SNOW ON THE
PLAINS. HIGH COUNTRY ACCUMULATIONS MINIMAL. MEANWHILE SATURDAY
TEMPS PROBABLY NOT MUCH WARMER THAN THOSE ON FRIDAY WITH ALL OFTHE
CLOUD COVER EXPECTED.

SUNDAY AND MONDAY...WARMER AND DRIER NORTHWEST FLOW MOVES OVER
THE AREA. SHOULD SEE AND END TO PRECIP EVEN IN THE HIGH COUNTRYBY
SUNDAY MORNING. FURTHERMORE COULD SEE STG AND GUSTY CHINOOK WINDS
IN THE NORTHERN FRONT RANGE FOOTHILLS SUNDAY NIGHT.

&&

.AVIATION...(FOR THE TAFS THROUGH 06Z WEDNESDAY EVENING)
ISSUED AT 820 PM MST TUE DEC 23 2014

NO AVIATION IMPACTS TONIGHT OR FRIDAY. NORTHERLY WINDS EARLY THIS
EVENING SHOULD TRANSITION TO SOUTHERLY BY MIDNIGHT AND THEN
CONTINUE THROUGH TOMORROW MORNING. CEILINGS AND VISIBILITIES WILL
BE UNLIMITED.

&&

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

$$

UPDATE...DANKERS/RTG
SHORT TERM...MEIER
LONG TERM...BAKER
AVIATION...DANKERS


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