Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 241821
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1121 AM MST WED DEC 24 2014

.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 336 AM MST WED DEC 24 2014

STRONG INVERSIONS WERE IN PLACE THIS MORNING WITH FOG IMPACTING
THE GUNNISON BASIN. THESE VALLEY INVERSIONS WILL REMAIN IN PLACE
INTO THURSDAY.

A BROAD RIDGE AXIS PASSES TODAY PRODUCING WARM ADVECTION ABOVE THE
INVERSIONS. FREE AIR WINDS BACK FROM NORTH TO WEST AND CLOUD
CEILINGS FORM AND THICKEN.

THE NEXT PACIFIC TROUGH WORKS THROUGH NORTHERN CALIFORNIA LATE
THIS AFTERNOON THEN THROUGH THE GREAT BASIN TONIGHT...CLOSING OFF
OVER CENTRAL UTAH ON THURSDAY. THIS STORM HAS DECENT COLD
AIR...-32C AT 500MB...BUT MARGINAL MOISTURE...0.35 PW. WHAT IT
LACKS IS GOOD DYNAMICAL ORGANIZATION. MOST OF THE JET ENERGY IS ON
THE BACKSIDE OF THE TROUGH SO A VERY SLOW PROGRESSION IS EXPECTED.

TONIGHT WINDS VEER TO SW AND STRENGTHEN. COLD ADVECTION ALOFT
BEGINS AFTER MIDNIGHT. THE ASSOCIATED WEAK COLD FRONT WORKS INTO
NE UTAH BEFORE SUNRISE THEN THROUGH THE REST OF EASTERN UTAH IN
THE MORNING AND WESTERN COLORADO THROUGH THE AFTERNOON. MOST
PRECIPITATION ON THURSDAY WILL BE SNOW DUE TO MORNING INVERSIONS
THEN AFTERNOON COLD ADVECTION. SE UTAH VALLEYS MAY SEE A RAIN SNOW
MIX. THE DENDRITIC CRYSTAL GROWTH REGION SATURATES AT AROUND 12KFT
OVER COLORADO THURSDAY AFTERNOON. THAT AND STEEP LOW 700-500 LAPSE
RATES OF 7.5 C/KM SHOULD PRODUCE SOME LOCALLY GOOD SNOWFALL RATES.

.LONG TERM...(THURSDAY NIGHT THROUGH TUESDAY)
ISSUED AT 336 AM MST WED DEC 24 2014

THE 00Z AND 06Z MODEL RUNS SEEM TO HAVE SOFTENED THE CHRISTMAS
STORM A BIT. MORE ENERGY IN THE FORM OF JET INFLUENCES AND UPLIFT
FROM PVA IS PUSHED FURTHER SOUTH AND IS RESIDENT OVER THE
FORECAST AREA ONLY BRIEFLY THURSDAY EVENING. THE MAIN TROUGH
MOVES NORTHEAST AND OUT OF THE AREA BY NOON FRIDAY WITH A
GENERALLY WEAK TROUGH REMAINING OVER WESTERN CO AND EASTERN UT
THROUGH FRI NIGHT. THE MODELS SHOW THE FLOW ALOFT AROUND
MOUNTAINTOP LEVEL SHIFTS TO NORTH AND NORTHEAST EARLY FRIDAY
MORNING AND WEAKENS QUITE A BIT. RIGHT NOW IT LOOKS LIKE ABOUT 2
DAYS OF RELATIVELY LIGHT PRECIPITATION WITH VERY LITTLE OROGRAPHIC
EFFECTS AND ONLY WEAK DYNAMICS TO SUPPORT PRECIPITATION. WILL STAY
WITH THE CURRENT SUITE OF WINTER STORM WATCHES...ANTICIPATING THAT
MOST WILL SHIFT TO ADVISORIES.

SATURDAY THROUGH TUESDAY...REMNANT MOISTURE AND SNOW SHOWERS
SHOULD GRADUALLY ERODE IN THE NORTHWEST FLOW OVER THE AREA ON SAT.
SAT NIGHT AND SUNDAY WILL SEE A BROAD EAST TO WEST FRONT AND
TROUGH STRETCH ACROSS THE NORTHERN TIER STATES AND MOVING
SOUTH...AFFECTING THE NORTHERN CO BORDER INITIALLY...THEN
DROPPING SOUTH THROUGH THE AREA SUN NGT AND MON. THIS SYSTEM SLOWS
DOWN OVER CO AND UT...AND MAINTAINS A FAIRLY STRONG WESTERLY WIND
ALOFT. THE COMBINATION OF TROUGH DYNAMICS AND OROGRAPHIC
ENHANCEMENTS MAKE THIS STORM ONE TO WATCH FOR SUN THROUGH THROUGH
TUE.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1106 AM MST WED DEC 24 2014

VFR CONDITIONS WILL REMAIN PROMINENT TODAY THOUGH SOME HIGH CLOUDS
WILL START STREAMING IN FROM THE NW AHEAD OF THE NEXT STORM SYSTEM.
EXPECT BKN TO OVC SKIES TO BE ON THE INCREASE THROUGH THE
AFTERNOON AND EVENING. THEY WILL START DROPPING OVERNIGHT REACHING
BETWEEN 5 TO 10K FEET BY MORNING. PRECIP CHANCES INCREASE AFTER
09Z WITH SOME -RA AND -SN POSSIBLE ACROSS MUCH OF THE AREA. TAF
SITES SHOULD NOT BE AFFECTED WITH ANY PRECIP UNTIL AFTER 12Z.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...WINTER STORM WATCH FROM THURSDAY MORNING THROUGH FRIDAY EVENING
     FOR COZ003-004-009-010-012-013-018-019.

UT...WINTER STORM WATCH FROM THURSDAY MORNING THROUGH FRIDAY EVENING
     FOR UTZ023.

&&

$$

SHORT TERM...JOE
LONG TERM...CC
AVIATION...TGR


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