Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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000
FXUS65 KBOU 202057
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
157 PM MST TUE JAN 20 2015

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 157 PM MST TUE JAN 20 2015

BIGGEST CONCERN SURROUNDS SNOWFALL POTENTIAL LATE TONIGHT AND
WEDNESDAY.

UNTIL THEN...THE EVENING FORECAST WILL BE MAINLY DRY WITH ONLY A
FEW SNOW SHOWERS POSSIBLE OVER THE PALMER DIVIDE AREA. THIS AREA
IS IN A FAVORABLE REGION OF WEAK FRONTOGENESIS. LOW LEVEL
CONVERGENCE ALSO AIDING THE THREAT OF LIGHT PRECIP THERE.

FOR LATER TONIGHT...MODELS ARE FAIRLY CONSISTENT BUT ALMOST ALL
HAVE CONTINUED THEIR SLIGHT NORTHWARD TREND. AN UPPER LEVEL
DISTURBANCE CLEARLY PRESENT IN SATELLITE IMAGERY IS MOVING ACROSS
NEVADA AND SOUTHERN CALIFORNIA....WHILE ANOTHER IS FORECAST TO
DROP QUICKLY SOUTHWARD ACROSS THE SPINE OF THE ROCKIES. THE TWO
PIECES OF ENERGY ARE EXPECTED TO MERGE JUST SOUTH OF THE FORECAST
AREA...BUT PERSISTENT WEAK Q-G LIFT IS NOTED FOR AN EXTENDED TIME
FROM LATE TONIGHT THROUGH ALL OF WEDNESDAY. AT THE SAME
TIME...ANTICYCLONIC UPSLOPE DEEPENS WITH A 10-15 KNOT NORTHEAST
WIND UP TO NEAR MOUNTAIN TOP LEVEL ON WEDNESDAY. LAPSE RATES ALSO
IMPROVE TO 6-7C/KM SO ATMOSPHERE SHOULD RESPOND NICELY TO ANY
OROGRAPHIC/Q-G FORCING. CROSS SECTIONS WOULD SHOW FAVORABLE
TEMPERATURE/OMEGA PROFILE FOR DENDRITIC GROWTH REGIME...ALTHOUGH
OMEGA IS A LITTLE ON THE WEAK SIDE. ONE THING GOING AGAINST
SNOWFALL WOULD BE SOME DRY LOW LEVEL AIR WHICH WEDGES ACROSS THE
NORTHEAST PLAINS. HOWEVER...AT THIS TIME MOST OF THAT SHOULD STAY
ON THE OTHER SIDE OF THE ANTICYCLONE WHICH WOULD ROUGHLY BE EAST
OF A FORT COLLINS TO AROUND LIMON. A FAIRLY SHARP CUTOFF IS
EXPECTED ON THE PLAINS. WE HAVE INCREASED POPS CONSIDERABLY
THROUGH THE COURSE OF THE DAY AND WILL CONTINUE TO DO SO IN/NEAR
THE FRONT RANGE BASED ON LATEST TRENDS AND FAVORABLE PARAMETERS
MENTIONED ABOVE. AT THIS TIME...WARMTH OVER THE LAST COUPLE DAYS
AND BULK OF SNOW DURING THE DAYTIME SHOULD HELP KEEP MAIN ROADS
WET. ACCUMULATIONS COULD APPROACH ADVISORY CRITERIA FROM PARK
COUNTY AND THE SOUTHERN FOOTHILLS TOWARD THE PALMER DIVIDE...BUT
WILL HAVE TO WATCH LATEST TRENDS CAREFULLY OVER THE NEXT 12 HOURS.
METRO DENVER HAS A GOOD THREAT OF 1-4 INCH AMOUNTS...HEAVIEST IN
THE WESTERN/SOUTHERN SUBURBS.

AREAS WEST OF THE FRONT RANGE MOUNTAINS...E.G. MOST OF JACKSON AND
GRAND COUNTIES...SHOULD STAY MAINLY DRY WITH WEAK DOWNSLOPE
COMPONENT AND LESS MOISTURE THERE.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 157 PM MST TUE JAN 20 2015

STRONGLY POSITIVELY-TILTED UPPER TROUGH AXIS STILL LOCATED FROM THE
DAKOTAS W/SW-WARD INTO NW COLORADO...WITH LARGE SCALE FORCING FOR
ASCENT CONTINUING OVER THE FORECAST AREA. MOISTURE DEPTH IS
BEGINNING TO LESSEN...BUT AMPLE ENOUGH OVER ABOUT THE SOUTHERN HALF
OF THE CWA. BOUNDARY LAYER WINDS STILL WITH A SLIGHT NNE-WARD
UPSLOPE COMPONENT AS WELL. ALL THAT TO SAY...EVENT WILL CERTAINLY BE
WINDING DOWN WITH REGARD TO INTENSITY BUT WILL KEEP A MID/HIGH
CHANCE POP FOR MUCH OF THE DENVER METRO AREA AT 00Z THU WITH LIKELY
POPS FOR THE S/SW FOOTHILLS AND PALMER DIVIDE AREAS. EXPECTING ONLY
AN ADDITIONAL DUSTING TO MAYBE A HALF-INCH OF SNOW AFTER 00Z THU FOR
DENVER PROPER...AND AROUND A HALF-INCH TO AN INCH FOR THE SW
FOOTHILLS AND PALMER DIVIDE AREAS. WILL LINGER LOW/MID CHANCE POPS
FOR THOSE FAVORED AREAS BY 06Z AND A SLIGHT CHANCE FOR THE DENVER
METRO...BUT THE EVENT SHOULD BE WINDING DOWN RAPIDLY BY THAT TIME
FRAME AS MOISTURE DEPTH QUICKLY ERODES AND BEST COMBO OF MOISTURE
DEPTH AND DYNAMICS CONTINUES TO PULL SOUTH AND EAST. SKIES WILL BE
CLEARING FROM NORTH TO SOUTH AS WELL...WITH ONLY SOME SCATTERED
CLOUDS PERHAPS OVER SOUTHERN ZONES BY 12Z THU. OVERNIGHT MINS APPEAR
ON TRACK WITH ONLY MINIMAL CHANGES FROM PREV FCST.

THURSDAY...FORCING FOR SUBSIDENCE MOVES OVERHEAD WITH NE FLOW ALOFT
AS SHARPLY-AMPLIFIED UPPER TROUGH CONTINUES TO THE SOUTH OF THE
FORECAST AREA. ONCE ANY LINGERING MORNING CLOUDS DISSIPATE...SHOULD
SEE A MOSTLY CLEAR SKY FOR MUCH OF THE AREA. ONLY CHANGE OF ANY
SIGNIFICANCE FROM PREV FCST WAS TO LOWER MAX TEMPS SEVERAL DEGREES
PER PROGGED 700MB TEMPS OF ABOUT -8C TO -10C...WHICH LATEST MOS
GUIDE IS SUPPORTING...COUPLED WITH A NOW-EXPECTED SNOW COVER OVER
THE CENTRAL/SOUTHERN PART OF THE FORECAST AREA. EXPECT HI TEMPS IN
THE UPPER 30S AT BEST IN THE DENVER METRO AND POTENTIALLY ONLY
REACHING THE MID 30S...COOLER OF COURSE OVER THE PALMER DIVIDE AND
PLATTE RIVER VALLEY AREAS. QUIET WEATHER CONTINUES OVERNIGHT
THURSDAY NIGHT BUT WILL BE SLIGHTLY WARMER WITH TEMPS BOTTOMING
OUT IN THE TEENS FOR THE METRO AREA AND COLDER IN THE USUAL
FAVORED COLD SPOTS.

COLORADO WILL REMAIN UNDER A NORTH TO NORTHWEST FLOW ALOFT ON
FRIDAY AND CONTINUING THROUGH THE WEEKEND. ANOTHER WEAK WAVE WILL
MOVE THROUGH THE FLOW ON FRIDAY BUT MOISTURE LOOKS LIMITED WITH
STRONG N-NW DOWNSLOPE FLOW. A SIMILAR SITUATION FOR SATURDAY NIGHT
WITH ONLY A SLIGHT CHANCE OF SNOW SHOWERS ON THE MOUNTAINS AND
NORTHEAST PLAINS. DRIER AND WARMER AGAIN MONDAY AND TUESDAY AS
HIGH AMPLITUDE RIDGING BUILDS OVER GREAT BASIN.

&&

.AVIATION...(FOR THE TAFS THROUGH 00Z WEDNESDAY LATE AFTERNOON)
ISSUED AT 157 PM MST TUE JAN 20 2015

VFR CONDITIONS WILL PREVAIL THROUGH 06Z...THEN CEILINGS ARE
EXPECTED TO GRADUALLY LOWER WITH ILS LANDING CONDITIONS DEVELOPING
08Z-11Z. EXPECT LIGHT SNOW TO BEGIN DEVELOPING IN THE AREA 10Z-13Z
WITH WIDESPREAD SNOW AND IFR CONDITIONS FOR THE FRONT RANGE
AIRPORTS THROUGH MOST OF THE DAY WEDNESDAY. AT THIS TIME EXPECT
TOTAL SNOW AMOUNTS 1-4 INCHES...LEAST TOWARD DIA AND MORE TOWARD
KAPA AND KBJC. ANTICYCLONIC FLOW PATTERN IN PLACE TO AND EAST TO
NORTHEAST COMPONENT FAVORED THROUGH MOST OF THIS TIME FRAME...BUT
HOLDING AT OR BELOW 10 KNOTS.

&&

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

$$

SHORT TERM...BARJENBRUCH
LONG TERM...GJG/ENTREKIN
AVIATION...BARJENBRUCH


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