Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 261710
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1010 AM MST FRI DEC 26 2014

.UPDATE...
ISSUED AT 1000 AM MST FRI DEC 26 2014

UPPER LEVEL CLOSED LOW WILL MOVE SLOWLY EAST ACROSS OUR FORECAST
AREA TODAY. PERIODS OF LIGHT SNOWFALL CONTINUE ACROSS MANY
LOCATIONS LATE THIS MORNING.  UNSTABLE LAPSE RATES (8 C/KM) THIS
AFTERNOON WILL ENHANCE SHOWERY NATURE OF PRECIPITATION FOR THE
REMAINDER OF THE DAY. THEREFORE...WILL ALLOW CURRENT HIGHLIGHTS
TO REMAIN IN EFFECT.

&&

.SHORT TERM...(TODAY THROUGH SATURDAY NIGHT)
ISSUED AT 408 AM MST FRI DEC 26 2014

THE COLD HEART OF THE STORM MOVES SLOWLY ACROSS THE FORECAST AREA
TODAY. THE UPPER LOW WAS NEAR THE FOUR CORNERS THIS EARLY
MORNING... THEN WILL OPEN AND WEAKEN THIS AFTERNOON AS IT BEGINS
TO SHIFT ONTO THE PLAINS. LARGE SCALE CYCLONIC MOTION REMAINS
OVER THE FORECAST AREA THROUGH TODAY. THE WRAP-AROUND NE FLOW
WORKED ACROSS THE NORTH OVERNIGHT AND THROUGH THE REMAINDER OF THE
AREA TODAY. THE CYCLONIC SHEAR IN THE HEART OF THE LOW WILL BE THE
CENTER OF WIDESPREAD SNOW PRODUCTION. THIS SHEARED/DEFORMATION
ZONE EXISTS FROM THE FLAT TOPS SOUTH TO PAGOSA SPRINGS TODAY AND
MATCHES THE WINTER STORM WARNINGS THAT ARE CURRENTLY IN EFFECT.

THE SOUTHERN PORTION OF THE SHEARED ZONE...ESPECIALLY EASTERN LA
PLATA...ARCHULETA...AND SOUTHERN HINSDALE COUNTIES...WILL SEE THE
STRONGEST COLD ADVECTION. THE -32C COLD CORE THERE PRODUCES
AFTERNOON LAPSE RATES APPROACHING 8 C/KM AND ADDS A STRONG
CONVECTIVE COMPONENT TO SNOW PRODUCTION. THE NORTHERN
PORTION...ESPECIALLY THE PARK RANGE/ZONE 4 MAY HAVE LIMITED SNOW
ACCUMULATIONS IN UNFAVORABLE EAST FLOW. HIGHLIGHTS ELSEWHERE WILL
LIKELY COME DOWN FROM WEST TO EAST THROUGH TODAY.

THIS EVENING THE LAST DISTURBANCES DROP THROUGH THE BACK OF THE
PROGRESSING TROUGH. OROGRAPHIC SNOW WILL CONTINUE TO FALL NEAR
THE CONTINENTAL DIVIDE THOUGH SIGNIFICANT ACCUMULATIONS WILL END
BY MIDNIGHT. UNDER LIGHT NORTH WINDS AND CLEARING SKIES...
TEMPERATURES WILL PLUMMET. HAVE SIGNIFICANTLY LOWERED TEMPERATURES
IN THE UINTAH AND GUNNISON BASINS. EARLY MORNING VALLEY FOG IS
POSSIBLE ACROSS THE FORECAST AREA.

A WEAK RIDGE PASSES ON SATURDAY BACKING THE WINDS ALOFT FROM
NORTH TO WEST. WARM ADVECTION OCCURS AT 500MB BUT 700MB AND BELOW
COLD AIR MASS SHOWS LITTLE MODIFICATION. SO ALL BUT THE HIGHEST
SLOPES REMAIN IN THE COLD INVERSIONS WITH CONTINUED BELOW NORMAL
TEMPERATURES. SATURDAY NIGHT...MOISTURE INCREASES IN STRENGTHENING
WEST FLOW AS THE NEXT NORTHERN PACIFIC WAVE DIGS THROUGH THE
PACIFIC NW. SHOWERS BEGIN OVER THE NW COLORADO MTNS. CLOUDS KEEP
THE OVERNIGHT LOWS NOT QUITE AS COLD.

.LONG TERM...(SUNDAY THROUGH THURSDAY)
ISSUED AT 408 AM MST FRI DEC 26 2014

THE COLD FRONT WITH ITS ASSOCIATED BAND OF CLOUDS AND
PRECIPITATION WILL CONTINUE MARCHING SOUTH SUNDAY. THE POLAR FRONT
SHOULD MOVE THROUGH THE FORECAST AREA DURING THE DAY AND BE SOUTH
OF THE AREA BY 12Z MONDAY...AS WILL THE POLAR JET STREAM. THE MAIN
VORT MAX AND BEST UPWARD MOTION IS PROJECTED TO TRAVEL OVER THE
AREA LATE MONDAY AFTERNOON AND EVENING. A BROAD SWATH OF MOISTURE
AND WEAK WESTERLY OROGRAPHIC FLOW WILL REMAIN OVER THE FORECAST
AREA THROUGH TUESDAY...WITH THE BEST MOISTURE OVER THE NORTHERN
HALF OF THE AREA ON MONDAY...SHIFTING TO THE SOUTH TUESDAY.

TUESDAY NIGHT AND WEDNESDAY THE GFS AND EC RETROGRADE A 500 MB
CLOSED LOW TO SOUTHERN CALIFORNIA. THE GFS ADOPTED A SOLUTION
SIMILAR TO AN EARLIER ECMWF RUN AND KEEPS THE CLOSED LOW FURTHER
EAST...OVER CA AND WESTERN NV. THE EC CAME IN AT 00Z WITH A
SOLUTION SIMILAR TO AN EARLIER GFS RUN...WHERE A DEEPER CLOSED
LOW MOVES FURTHER WEST TO A POSITION ALONG OR JUST OFF THE CA
COAST. BOTH MODELS LEAVE A DEFORMATION ZONE OVER THE FORECAST
AREA. THE GFS CONCENTRATES THE DEFORMATION ZONE CLOUD AND PRECIP
CHANCES OVER SW CO AND SE UT TUE AND TUE NIGHT....WHILE THE EC
PLACES THESE OVER NE UT AND NW CO DUE TO THE GREATER ROTATION OF
THE ENTIRE SYSTEM BY THE DEEPER LOW ALONG THE WEST COAST.

WED NIGHT AND THURSDAY...THE GFS MOVES THE LOW EAST INTO AZ AND
NEW MEXICO...WITH MOISTURE AND CLOUD AFFECTING MAINLY SE UT AND SW
CO. THE EC LEAVES ITS DEEPER LOW OVER SOUTHERN CA THRU THURSDAY
AND BRINGS A SIGNIFICANT AMOUNT OF MOISTURE INTO UT AND CO VIA THE
EASTERN PACIFIC...WEST AND SOUTH OF THE BAJA PENINSULA. SO THE
DIFFERING SOLUTIONS PRODUCE A GOOD DEAL OF UNCERTAINTY IN THE
FORECAST FOR WED AND THU.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 408 AM MST FRI DEC 26 2014

FREQUENT SNOWFALL WILL CONTINUE THROUGH THIS AFTERNOON FOR ALL TAF
SITES...WITH MVFR CIGS AND VSBYS PREVAILING. LOCAL CONVECTIVE
SHOWERS WILL CAUSE BRIEF IFR CONDITIONS AT KASE...KEGE...KDRO...
KTEX...AND KRIL. THE MOUNTAINS WILL REMAIN OBSCURED. CONDITIONS
SHOULD IMPROVE ACROSS EASTERN UTAH AFTER 06Z TONIGHT AND GRADUALLY
SPREAD EAST.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER WEATHER ADVISORY UNTIL 6 PM MST THIS EVENING FOR COZ001-
     002-007-011.

     WINTER WEATHER ADVISORY UNTIL 3 PM MST THIS AFTERNOON FOR COZ006-
     020.

     WINTER STORM WARNING UNTIL MIDNIGHT MST TONIGHT FOR COZ004-009-
     010-012-013-019-022-023.

     WINTER WEATHER ADVISORY UNTIL MIDNIGHT MST TONIGHT FOR COZ003-
     005-008-014-017-018.

UT...WINTER WEATHER ADVISORY UNTIL 6 PM MST THIS EVENING FOR UTZ023-
     025-028.

     WINTER WEATHER ADVISORY UNTIL 3 PM MST THIS AFTERNOON FOR UTZ024-
     027-029.

&&

$$

UPDATE...MPM
SHORT TERM...JOE
LONG TERM...CC
AVIATION...CC



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