Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 010344
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
844 PM MST SAT JAN 31 2015

.UPDATE...
ISSUED AT 827 PM MST SAT JAN 31 2015

RADAR HAS INDICATED AN INCREASE IN SNOW SHOWERS OVER LARIMER AND
WELD COUNTIES DURING THE PAST HOUR WHILE MOUNTAIN SNOW SHOWERS
ALSO SHOWING AN UP TIC IN COVERAGE. THIS IN RESPONSE TO STRONG
JET ALOFT WHICH HAS JUST NOSED INTO NORTHERN COLORADO. STRONGER
COLD FRONTAL PUSH APPEARS TO BE ACROSS FAR SOUTHEAST WYOMING AS
WINDS NOW GUSTING TO 31KT AT CYS. THESE STRONGER NORTHEAST WINDS
WILL PUSH SOUTHWARD ACROSS THE NORTHEAST PLAINS THROUGH THE NIGHT
AS WINDS SHIFT AND INCREASE FROM NORTH AND NORTHEAST. EXPECT SNOW
SHOWERS TO EXPAND SOUTHWARD INTO THE DENVER AREA IN NEXT FEW HOURS
WITH BEST CHANCE OF ACCUMULATING SNOW FROM 11 PM TO 4 AM. SHOWERS
HAVE A CONVECTIVE NATURE AS AIRMASS HAS DESTABILIZED A BIT WITH
00Z DEN SOUNDING SHOWED QUITE A BIT OF COLD ADVECTION ALOFT DURING
THE DAY.

MAIN CHANGE TO FORECAST WAS TO TWEAK EVENING HOURS WITH LATEST
TRENDS BUT OVERALL SNOW AMOUNTS STILL LOOK GOOD IN THE 1-3 INCH
RANGE. HIGHEST AMOUNTS WILL BE UNDER BANDED SNOWFALL. ALSO
INCREASED SNOW CHANCES IN THE HIGHER MOUNTAINS WITH GOOD
OROGRAPHIC FLOW ESPECIALLY IN ZONE 33. SNOW WILL DECREASE LATER
TONIGHT AS JET MOVES EAST AND STRONGER SUBSIDENCE DEVELOPS WITH
DIMINISHING UPSLOPE FLOW.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 154 PM MST SAT JAN 31 2015

SHOWER ACTIVITY DEVELOPING THIS AFTN AS A SPLITTING TROUGH WITH
WEAK DEFORMATION ZONE OVER THE CWA SHIFTS TO THE EAST. BEST CHC OF
SNOW WL BE OVER THE PALMER DIVIDE SOUTH AND EAST OF DENVER. DRIER
AIR WILL PUSH IN FROM THE NORTHWEST AHEAD OF THE NEXT SYSTEM. THE
NEXT SYSTEM DROPS INTO NORTHERN COLORADO FM WYOMING THIS EVENING.
THE COLD FRONT IS EXPECTED TO REACH DENVER IN THE 03-04Z TIME
FRAME WITH NORTH TO NORTHEAST UPSLOPE WINDS IN ITS WAKE. IN
ADDITION THE NOSE OF 90 KT UPPER LEVEL JET WILL TRANSLATE EAST
ACROSS NORTHERN COLORADO TONIGHT INTO SUNDAY MORNING SO THERE
COULD BE A PERIOD OF SOME ENHANCED SNOW BANDS. THE BEST WINDOW FOR
SNOW WL BE FROM 05Z-12Z. INCREASING SUBSIDENCE WILL OCCUR ON
SUNDAY WITH A DRIER NORTHWESTERLY FLOW ALOFT OVER NORTHERN
COLORADO. TEMPERATURES WILL BE RUNNING COOLER THAN NORMALS WITH
HIGHS GENERALLY IN THE 30S.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 154 PM MST SAT JAN 31 2015

MOISTURE AND WIND INCREASE OVER THE MOUNTAINS MONDAY MORNING AS A
MOIST NORTHWESTERLY FLOW ALOFT SETS UP OVER COLORADO. THIS PATTERN
WILL BRING PERIODS OF SNOW TO THE HIGH COUNTRY FROM MONDAY THROUGH
WEDNESDAY. SNOWFALL AMOUNTS SHOULD REMAIN ON THE LIGHT SIDE DUE TO
POOR LAPSE RATES AND LACK OF MOISTURE DEPTH AT TIMES.
HOWEVER...COULD SEE BRIEF PERIODS OF HEAVIER SNOW AT TIMES. WINDY
CONDITIONS ARE ALSO EXPECTED OVER THE MOUNTAINS AND FOOTHILLS FROM
EARLY MORNING MONDAY THROUGH NOON ON TUESDAY. LOOKS LIKE IT WILL
BE WINDIEST FROM THE EASTERN SLOPES OF THE MOUNTAINS INTO THE
HIGHER FOOTHILLS. AT THIS TIME IT LOOKS LIKE WINDS SHOULD REMAIN
BELOW WARNING CRITERIA. THIS DOWNSLOPE FLOW WILL PRODUCE MILD AND
DRY WEATHER FOR AREAS EAST OF THE MOUNTAINS MONDAY AND TUESDAY.

BY WEDNESDAY...THE MODELS BEGIN TO DIVERGE SOMEWHAT. BOTH THE GFS AND
THE ECMWF SHOW AN UPPER LEVEL DISTURBANCE AND ASSOCIATED COLD FRONT
MOVING ACROSS THE NORTHERN AND CENTRAL ROCKIES. THE GFS IS MORE
AMPLIFIED WITH THIS SYSTEM AND PLACES THE UPPER JET 300 MILES
FURTHER TO THE SOUTH THAN THE ECMWF. AS A RESULT...THE GFS HAS MUCH
MORE QG LIFT OVER NORTHERN COLORADO...WITH THE ECMWF HAVING WEAKER
LIFT FURTHER TO THE NORTH OVER WYOMING. IF THE GFS PANS OUT...WOULD
SEE HEAVY BANDS OF SNOW OVER NORTHERN SECTIONS OF THE NORTHEASTERN
PLAINS FROM LARIMER COUNTY EASTWARD INTO SEDGWICK AND PHILLIPS
COUNTIES. THE ECMWF SHOWS MUCH LESS SNOW AND KEEPS IT CONFINED TO
AREAS JUST ALONG THE WYOMING AND NEBRASKA BORDERS. DO TO THE
UNCERTAINTY OF THE MODELS...HAVE ONLY RAISED POPS IN THESE AREAS TO
SCATTERED. MODELS SHOW AN UPPER LEVEL HIGH PRESSURE RIDGE BUILDING
INTO THE ROCKY MOUNTAIN REGION BY LATE IN THE WORK WEEK WITH MUCH
WARMER AND DRIER WEATHER MOVING INTO THE AREA. TEMPERATURES COULD
POSSIBLY REACH THE LOWER 70`S ACROSS PORTIONS OF THE FRONT RANGE
URBAN CORRIDOR ON FRIDAY. THEREFORE...HAVE RAISED FRIDAY MAX
TEMPS.|

&&

.AVIATION...(FOR THE TAFS THROUGH 06Z SUNDAY EVENING)
ISSUED AT 827 PM MST SAT JAN 31 2015

SCATTERED SNOW SHOWERS DEVELOPING RAPIDLY TO THE NORTH OF
TERMINALS AND EXPECT SNOW SHOWERS BETWEEN 04-06Z. BEST CHANCE OF
ACCUMULATING SNOW AND LOWEST CIGS/VSBYS BETWEEN 06Z-10Z. SNOWFALL
AMOUNTS 1-2 INCHES ON GRASSY SURFACES...BUT WITH HEAVIER BANDS OF
SNOW COULD ACCUMULATE A SLUSHY INCH ON RUNWAY SURFACES. SNOW
DIMINISHING LATER TONIGHT WITH IMPROVING CONDITIONS AROUND
DAYBREAK. COLD FRONT WILL PUSH THROUGH TERMINALS BETWEEN 06-07Z
WITH NE WINDS 15-25KT.

&&

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

$$

UPDATE...ENTREKIN
SHORT TERM...COOPER
LONG TERM...JK
AVIATION...ENTREKIN


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