Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 261105
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
405 AM MST THU FEB 26 2015

.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 403 AM MST THU FEB 26 2015

THE NEXT SHORTWAVE FROM THE NORTHWEST IS REACHING INTO NORTHERN
UTAH THIS MORNING AS SEEN ON CURRENT SATELLITE IMAGERY. THIS
SYSTEM WILL BE ENTERING EASTERN UTAH LATE THIS MORNING AND
WESTERN COLORADO DURING THE AFTERNOON. DAYTIME HEATING SHOULD AID
IN THE DEVELOPMENT OF SHOWERS THIS AFTERNOON...SIMILAR TO 24
HOURS AGO WHEN SCATTERED SHOWERS DEVELOPED ACROSS MOUNTAIN TERRAIN
OF NORTHEAST UTAH AND NORTHWEST COLORADO AND TRACKED SOUTHEAST
THROUGHOUT THE DAY.

TONIGHT INTO TOMORROW...A BREAK IN SHOWERS IS EXPECTED WITH
STABILITY INCREASING THROUGH THE OVERNIGHT HOURS BEFORE THE
CHANCE OF PRECIP INCREASES ON FRIDAY WITH THE APPROACH OF UNSTABLE
AIR. DID ADD CO ZONE 9...17...AND 21 AS WELL AS UT ZONE 28 ABOVE
7500 FT INTO WINTER STORM WATCH. THOUGH MANY NORTH-FACING AREAS
OF ZONE 9 WILL BE BLOCKED FROM HEAVY SNOW DUE TO SOUTHWEST
FLOW...EXPECTING THE TOP AND SOUTHWEST END OF THE GRAND MESA TO DO
WELL. NOTICED A SIMILARITY IN FORECAST DATA FOR THIS SYSTEM WITH
THE STORM LAST WEEKEND IN THE SOUTHERN VALLEYS WHERE WAA WILL
OCCUR...MOS GUIDANCE IS IN THE 40S...YET FORECAST SOUNDINGS ARE
PRETTY MUCH BELOW FREEZING MOST OF THE EVENT EXCEPT FOR A COUPLE
OF HOURS. THEREFORE...DECREASED HIGH TEMPS IN THESE AREAS FOR
FRIDAY THINKING THAT MOS GUIDANCE IS TOO WARM. WINTER STORM
WATCHES MAY START A BIT TOO EARLY AT THIS POINT...BUT WITH SO MUCH
MOISTURE AND UNORGANIZED ENERGY PROGGED DID NOT FEEL CONFIDENT AT
THIS POINT TO PUSH IT BACK TO LATER IN THE DAY FRIDAY.
HOWEVER...THE FASTER ACCUMULATING SNOWFALL IS EXPECTED TO OCCUR
LATER IN THE DAY ON FRIDAY...ESPECIALLY IN THE SOUTHERN VALLEYS OF
COLORADO. KEPT SOUTHEAST UTAH VALLEYS OUT OF WATCH SINCE THIS
STORM DOES NOT HAVE THE STRONG DYNAMICS SEEN IN THE LAST STORM
UNTIL LATER IN THE WEEKEND. SEE LONG TERM SECTION FOR MORE ON THIS
EXTENDED ACTIVE PERIOD OF WEATHER.



.LONG TERM...(FRIDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 403 AM MST THU FEB 26 2015

A LONG-DURATION PRECIPITATION EVENT IS STILL ON TRACK TO IMPACT THE
FORECAST AREA THROUGH THE FIRST HALF OF NEXT WEEK. A LARGE POSITIVE-
TILTED TROUGH DEVELOPS OVER THE FAR WEST THIS WEEKEND THEN EJECTS
EASTWARD ON MONDAY...ONLY TO BE FOLLOWED BY ANOTHER TROUGH DROPPING
THROUGH FROM THE NORTHWEST TUE-WED. THE PRIMARY FOCUS...AT LEAST
THROUGH THE WEEKEND...APPEARS TO BE SOUTHWEST COLORADO NORTH TO
GRAND MESA BUT WITH UNCERTAINTY IN SNOW LEVELS TOWARD THE FOUR
CORNERS AREA. SOUTHWEST FLOW WILL NOT BE AS FAVORABLE FOR MANY
NORTHERN AREAS. A WINTER STORM WATCH HAS BEEN ISSUED FOR MUCH OF
THIS AREA AS WELL AS FOR THE ABAJO/LA SAL MTNS IN SE UT.

SHORTWAVE ENERGY TOPPING THE PACIFIC RIDGE AND DROPPING SOUTHWARD
ALONG THE WEST COAST WILL CONTINUE TO CARVE OUT A LARGER TROUGH OVER
THE FAR WEST AND GREAT BASIN FRI NIGHT AND SATURDAY. AS THIS TROUGH
DIGS SOUTHWARD...IT WILL LIFT A DOWNSTREAM UPPER JET NORTHWARD INTO
OUR FORECAST AREA SATURDAY. STRENGTHENING OROGRAPHIC SOUTHWEST FLOW
COUPLED WITH INCREASING JET LEVEL DIVERGENCE AND A MOISTENING
DENDRITIC SNOW GROWTH ZONE SHOULD BRING MTN SNOW AND VALLEY
RAIN/SNOW TO SE UT AND SW CO FRI NIGHT AND SAT. DECIDED TO INCLUDE
CO ZONE 21 (CORTEZ...DOVE CREEK AND VICINITY) TO THE WINTER STORM
WATCH...THOUGH 700 MB WARM ADVECTION IN THE SOUTHWEST FLOW CAUSES
UNCERTAINTY FOR SNOW LEVELS IN THE SOUTH AND ESPECIALLY FOR
ELEVATIONS BELOW ABOUT 6000 FEET. ALSO ADDED GRAND MESA AN
UNCOMPAHGRE PLATEAU TO THE WATCH AS 00Z MODELS APPEARED TO PUSH
PRECIPITATION FARTHER NORTH ON SATURDAY. LAPSE RATES STEEPEN
ENOUGH THAT I WAS TEMPTED TO ADD ISOLATED THUNDERSTORMS FOR SAT
GIVEN MUCH OF THE AREA WAS ALSO IN THE DAY 3 CONVECTIVE OUTLOOK
FROM SPC.

MODELS SHOW A 700 MB OVER NRN UT THAT GETS SHEARED OUT ACROSS NE UT
AND NW CO SAT NIGHT BEFORE LIFTING INTO WY ON SUNDAY. WEAK LOW LEVEL
CONVERGENCE POSSIBLE ALONG THIS CONVERGENT AXIS FOR A BETTER CHANCE
OF PRECIP ACROSS THE NORTH SAT NIGHT IF IT MATERIALIZES. SOMETHING
TO WATCH.

THE FAR WESTERN TROUGH IS EXPECTED TO DROP TO SRN CA BY SUNDAY
EVENING. MODELS SHOW A DOWNSTREAM RISE IN MID-LEVEL HEIGHTS OVER THE
CWA AND AN ATTEMPT AT WORKING SOME DRIER AIR INTO THE AREA IN THE
PERSISTENT SOUTHWEST FLOW. LOOKS LIKE A DECREASE IN ACTIVITY IS
POSSIBLE SUNDAY AS A RESULT...AND STILL STRUGGLES WITH SNOW LEVELS.
BUT THE WESTERN TROUGH THEN LIFTS NORTHEAST AND ACROSS OUR AREA
TOWARD MONDAY NIGHT FOR ANOTHER ROUND OF PRECIPITATION MONDAY.
ANOTHER TROUGH DROPS IN FROM THE PACIFIC NW AND BEHIND IT FOR A
CONTINUED CHANCE OF PRECIP TUE-WED.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 403 AM MST THU FEB 26 2015

KDRO MAY EXPERIENCE SOME FOG EARLY THIS MORNING...AND LINGERING LOW
CLOUDS IN NORTHERLY FLOW AT KASE MAY PRODUCE PERIODS OF MVFR CIGS
THERE. OTHERWISE...TAF SITES ARE EXPECTED TO BE VFR THROUGH 18Z
TODAY. SCATTERED -SHSN WILL BE MAINLY OVER THE MTNS FOR THE PERIOD
18Z-00Z THIS AFTERNOON AS THE NEXT UPPER DISTURBANCE APPROACHES. ALL
TAF SITES HAVE A CHANCE OF RECEIVING PRECIPITATION AFTER 00Z
THURSDAY EVENING. SNOW IS LIKELY ALONG THE NORTHERN AND CENTRAL
DIVIDE FROM K3MW TO KMYP AFTER ABOUT 20Z.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER STORM WATCH FROM FRIDAY MORNING THROUGH MONDAY EVENING
     FOR COZ009-012-014-017>019-021>023.

UT...WINTER STORM WATCH FROM FRIDAY MORNING THROUGH MONDAY EVENING
     FOR UTZ028.

&&

$$

SHORT TERM...JAM
LONG TERM...JAD
AVIATION...JAD



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