Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 240500
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1000 PM MST MON FEB 23 2015

.SHORT TERM...(TONIGHT THROUGH TUESDAY NIGHT)
ISSUED AT 345 PM MST MON FEB 23 2015

THE MAIN UPPER LOW WAS OVER CENTRAL CA THIS AFTERNOON. SURFACE
TROUGH ANALYZED FROM JUST SOUTH OF THE FOUR CORNERS UPO TOWARD
KREMMLING. GOOD PLUME OF CLOUDS IN DIFFLUENT FLOW EXTENDED FROM
CENTRAL AZ INTO SE UT AND FAR SW CO LIKELY CONTAINING SOME LOCALLY
MODERATE-HEAVY SNOW. BUT SURFACE OBS/WEBCAMS/VISIBLE SATELLITE HAVE
ALSO INDICATED A RATHER RAPID CONTRACTION OF THE WIDESPREAD SNOW
BACK TO TOWARD THE FOUR CORNERS WITH HINTS OF A TRANSITION TO MORE
CONVECTIVE NATURE. WITH MODELS INDICATING A WEAKENING IN SYNOPTIC
FORCING AND 700 MB MOISTURE CONVERGENCE THIS EVENING...HAVE
CANCELLED THE WINTER STORM WARNINGS FOR THE CENTRAL MTNS AND VALLEYS
(CO ZONES 9/10/11/12 AND 14. MOSTLY CLEAR SKIES TONIGHT WILL
BE ACROSS NE UT AND FAR NW CO.

MODELS INDICATING A LULL IN THE ACTIVITY OR JUST SOME LIGHT SNOW
THIS EVENING ACROSS SE UT/SW CO. ANOTHER BURST OF A COUPLE INCHES OF
SNOW THEN EXPECTED TOWARD SUNRISE FOR FAR SE UT AND SW CO AS THE
MAIN UPPER LOW CURRENTLY OVER CENTRAL CA MOVES ACROSS NRN AZ INTO
CENTRAL NM. DEBATED EXTENDING THE WINTER STORM WARNING FOR THE FAR
SOUTH THROUGH TUE MORNING BUT ALSO CONCERNED ABOUT OVER-WARNING...
AND THAT CONCERN WAS SUPPORTED BY CALLS TO A COUPLE SW CO EMERGENCY
MGRS. WILL KEEP THE CURRENT EXPIRATION TIMES...BUT THE EVENING SHIFT
WILL NEED TO MONITOR.

SNOW CHANCES SHOULD TAPER DOWN TUE AFTERNOON.WILL GO BELOW TEMP
GUIDANCE FOR HIGHS ON TUESDAY ESPECIALLY WHERE DEEP NEW SNOW COVER
EXISTS. TUE NIGHT WILL BE IN BETWEEN SYSTEMS UNDER NORTHWEST FLOW.
NEXT SHORTWAVE TROUGH WILL BE APPROACH THE NORTH BY WED MORNING.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 345 PM MST MON FEB 23 2015

THE FLOW PATTERN ACROSS NOAM WILL MAINLY BE DOMINATED BY A LARGE
BROAD TROUGH FROM LATE WEEK ONWARD...MEANING THE PROBABILITY OF
COOLER THAN AVERAGE TEMPERATURES AND STORMY CONDITIONS WILL BE ON
THE HIGH SIDE OVER MUCH OF THE LOWER 48. TO THE WEST...AN AMPLIFIED
RIDGE WILL BE LOCATED NEAR THE 145W MERIDIAN DURING THIS TIME...A
SIGNAL THAT THE ARCTIC HAS A FREE PASS TO DROP SOUTHWARD. WEDNESDAY
IS THE TRANSITION DAY. THE CURRENT SYSTEM AFFECTING OUR CWA WILL
BE QUICKLY SWEPT EASTWARD ACROSS THE GULF STATES...WHILE THE NEXT
POSSIBLE MAJOR STORM SYSTEM WILL MOVING ACROSS THE GULF OF ALASKA.
THE WESTERN RIDGE WILL BE BROADER ON WEDNESDAY INTO THURSDAY
ALLOWING THE NORTHWEST FLOW ALOFT TO TRANSPORT BOTH PACIFIC
MOISTURE AND ARCTIC ENERGY THROUGH THE ROCKIES. THE INITIAL
COMBINATION OF THE ABOVE ARRIVES ON WEDNESDAY INTO WEDNESDAY
NIGHT BUT IS COMING MORE FROM THE COLD CONTINENTAL PART OF NOAM.
AS SUCH THE PWAT IS NOT AS ROBUST AS THE PAST SYSTEM AND THE MAIN
ENERGY IS JUST TO THE NORTHEAST OF OUR CWA. A COMBINATION OF GUSTY
WINDS AND SNOW COULD BE ENOUGH TO PRODUCE SOME WINTER IMPACTS FROM
VAIL PASS UP TO WYOMING. AFTER A WHAT APPEARS TO BE A SHORT BREAK
ON THURSDAY AS THE NEXT STRONG BRANCH OF THE POLAR JET NOSES INTO
THE PACIFIC NORTHWEST. THE ARRIVAL OF THIS JET TO THE WEST COAST
WILL ALLOW ENERGY IN THE FLOW TO CUT OUT ANOTHER TROUGH ACROSS THE
INTERMOUNTAIN WEST BEGINNING THURSDAY NIGHT WHICH AGAIN PERSISTS
THROUGH THE WEEKEND PERIOD. A VERY SIMILAR SCENARIO AS THE CURRENT
STORM SYSTEM WOULD BE THE RESULT. THE MODELS ARE PAINTING SOME
DECENT PRECIPITATION ON THE UPSTREAM CURVE OF THIS TROUGH EARLY
SATURDAY THROUGH SUNDAY. THE ONLY PROBLEM IS THE AXIS OF THE
HEAVIEST QPF IS NOT ALIGNED BETWEEN THE EURO AND GFS IN THE LATEST
RUNS. THE GFS SUPPORTS THE 4 CORNERS INTO THE SAN JUANS HILLS AND
SOUTHERN VALLEYS...WHILE THE EURO IS DISPLACED TO THE SOUTHEAST.
THESE TRENDS WILL BE CLOSELY MONITORED THE NEXT FEW DAYS THOUGH
POPS ARE ALREADY REPRESENTED IN THE FORECAST. OTHERWISE WILL BE
BATTLING TEMPERATURES AND POSSIBLE AREAS OF FOG WITH THE NEW SNOW
COVER.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1000 PM MST MON FEB 23 2015

SNOW WILL CONTINUE OVER THE MOUNTAINS OF SOUTHEAST UT AND
SOUTHWEST CO SOUTHWARD TO THE AZ AND NM BORDERS THROUGH 18Z
TUE...THEN WILL DIMINISH FROM THE NORTH. THIS SNOW WILL GENERALLY
BE ON THE LIGHT SIDE...BUT BRIEF PERIODS OF MVFR OR EVEN IFR
CONDITIONS WILL BE POSSIBLE AT KTEX AND KDRO. ALSO SOME SNOW
SHOWERS WILL CONTINUE NORTHWARDS TOWARDS THE CENTRAL CO MOUNTAINS
UNTIL AROUND 10Z AFFECTING KASE AND KMTJ. PATCHY FOG MAY ALSO BE
A CONCERN UNTIL AROUND 18Z TUE IN THE VALLEYS SOUTH OF A LINE FROM
AROUND KGJT TO KGUC. BY TUE AFTERNOON VFR CONDITIONS SHOULD
DOMINATE. HOWEVER BRIEF MTN OBSCURATIONS MAY OCCUR ACROSS THE
SOUTHERN MOUNTAINS IN SCATTERED TO ISOLATED SNOW SHOWERS THROUGH
00Z WED.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER STORM WARNING UNTIL MIDNIGHT MST TONIGHT FOR COZ017>023.

UT...WINTER STORM WARNING UNTIL MIDNIGHT MST TONIGHT FOR UTZ022-029.

     WINTER STORM WARNING UNTIL 6 AM MST TUESDAY FOR UTZ028.

&&

$$

SHORT TERM...JAD
LONG TERM...15
AVIATION...EH


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