Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 011747
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1047 AM MST SUN MAR 1 2015

.UPDATE...
ISSUED AT 1010 AM MST SUN MAR 1 2015

I AM AT THE MERCY OF THE SHORT TERM ATTM AND WILL BE USING
SATELLITE AND RADAR AND SURFACE OBS FOR TRENDS IN THIS COMPLICATED
STORM SYSTEM. LOOKING AT SOME OF OUR CURRENT FORECASTS COMPARED TO
REAL TIME AND FUTURE EXPECTATIONS SOME OVER-HAULING IS NECESSARY.
THE SOUTHERN CWA REMAINS THE FOCUS JUST BECAUSE OF THE CURRENT
LARGE SCALE SET UP WITH SOUTHERLY FLOW IN PLACE. HOWEVER WARM
ISENTROPIC UPGLIDE OVER THE COLDER AIRMASS IN THE NORTHERN VALLEYS
PRODUCES AS MUCH IF NOT MORE SNOW THAN THE SOUTH OVERNIGHT.
METEOROLOGY IS FUN IF NOT HUMBLING OFTEN. SO CHALLENGE TODAY IS
SNOW LEVEL...SNOW LEVEL...SNOW LEVEL. 300K THETA LEVELS ARE
SHOWING THE GOOD MOISTURE PUSH ONGOING ACROSS THE 4 CORNERS ATTM.
PWATS OVER HALF OF AN INCH AT ABQ OVER 200 PERCENT OF NORMAL...FGZ
IS 0.44 NEARING 200 PERCENT OF NORMAL. THIS IS COMING OUR WAY AND
LARGE SCALE ASCENT IN THE ENTRANCE REGION OF THE JET LOOKS
PROMISING. WHAT CONCERNS ME IS SNOW LEVEL...SNOW LEVEL...SNOW
LEVEL. THIS MOISTURE IS GOOD FOR MAKING SNOW UP HIGH AND EXPECT
WHAT HAS BEEN 14:1 OR SO SNOW RATIOS IN THE HIGH COUNTRY TO LOWER
CLOSER TO 11:1. SO MORE MOISTURE MAY MEAN SLIGHTLY LESS SNOW
ACCUMULATION. SECOND...PRECIP TYPE...MORE MOISTURE WILL PUSH DEW
POINTS OVER FREEZING IN THE LOWER VALLEYS. RAIN IS MORE LIKELY FAR
SOUTH AND MAY MIX AS HIGH AS 6500 OR SO FEET TODAY. SREF PLUMES
SUGGEST RAIN IS THE MORE LIKELY METEOR AT CEZ AND DRO THIS
AFTERNOON. LASTLY THE MOST IMPORTANT FACTOR WITH THIS STORM SO
FAR...INSTABILITY. IT IS THERE NOW AND INCREASES THIS AFTERNOON
AND OVER-RIDES SO MANY FORECASTS AS IT COULD PUSH SNOW LEVELS BACK
DOWN WITH INTENSE RATES TO BOOT. FORT LEWIS CAMS SHOW BIG FAT
FLAKES RIGHT NOW...CONVECTION. MODELS ALL AGREE ON AFTERNOON PUSH
IN THE SOUTHERN MOUNTAINS AND SOUTHEAST UTAH...SO HAVE TRENDED
CURRENT FORECAST THAT WAY AND HANG ON FOR THE RIDE.

UPDATE ISSUED AT 608 AM MST SUN MAR 1 2015

THE SNOWFALL DIMINISHED IN THE MONTROSE VICINITY AND THE WINTER
WEATHER ADVISORY WAS ALLOWED TO EXPIRE. A FEW NARROW BANDS OF
SNOW SHOWERS WILL PASS OVER THE AREA THIS MORNING...BUT SHOULD
YIELD LESS THAN AN INCH OF NEW SNOW.

&&

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 519 AM MST SUN MAR 1 2015

SOME SCATTERED SHOWERS STILL LINGERING EARLY THIS MORNING OVER
THE TAVAPUTS AND UNCOMPAHGRE PLATEAUS AND ADJACENT VALLEYS ALONG
THE JET STREAK AXIS WITH A WEAK TROUGHY FEATURE AT 700MB. THE ULJ
WILL REMAIN OVER EASTERN UT AND WESTERN CO THROUGHOUT THE DAY BUT
REALLY ENHANCE ON MONDAY WITH A 140 TO 150 KT JET STREAK ACROSS
THE FOUR CORNERS BY THE AFTERNOON.

CURRENT IR AND WATER VAPOR SATELLITE IMAGERY LOOKING QUITE
EXCITING AS CLOUD TOP ENHANCEMENT OCCURS OVER NORTHERN ARIZONA.
THIS MOISTURE IS BEGINNING TO SHOW UP ON THE KGJX RADAR REACHING
INTO THE NORTHERN SAN JUANS. THE FEW SHOWERS NORTH OF THE SAN JUAN
MOUNTAINS THIS MORNING WILL BE JOINED BY A MUCH MORE IMPRESSIVE
SWATH OF PRECIPITATION LATE THIS AFTERNOON. CONTINUED CURRENT
HAZARDS AND UPGRADED WINTER WX WATCHES TO WARNINGS ACROSS THE
NORTHERN MOUNTAINS AND VALLEYS OF NORTHWEST COLORADO STARTING
TONIGHT. DECIDED TO LEAVE THE EASTERN UINTA BASIN OUT OF THE
WARNING WITH FORECAST DATA ONLY AROUND 2 INCHES FOR VERNAL. MAY
NEED TO CONSIDER AN ADVISORY...BUT CONFIDENCE NOT HIGH ENOUGH FOR
MORE THAN 2 INCHES OF SNOW AT THIS POINT IN TIME WITH OROGRAPHIC
SHADOWING BEING SUGGESTED ON A LOT OF THE FORECAST MODELS FOR THE
EASTERN UINTA VALLEY. A RAIN/RAIN-SNOW MIX IS VERY MUCH POSSIBLE
IN CORTEZ TODAY AND POTENTIALLY DURANGO AS WELL AS H7 TEMPERATURES
INCREASE ALL THE WAY TO -1.5C.

THE UPPER LEVEL TROUGH PULLING IN PACIFIC MOISTURE AND ENERGY FOR
THIS SYSTEM WILL GRADUALLY MOVE EAST ON MONDAY. THE TROUGH
ACTUALLY WEAKENS SLIGHTLY...BUT THE GRADIENT STRENGTHENS OVER
EASTERN UTAH AS THE 140 KT JET STREAK MENTIONED ABOVE PUSHES
PRETTY SUBSTANTIAL 4+ G/KG MOISTURE INTO THE FOUR CORNERS. SNOW
LEVELS WILL ONCE AGAIN BE A CHALLENGE BOTH TODAY AND MONDAY...WITH
THE WARMEST AIR OVER THE AREA THIS EVENING THROUGH MONDAY MORNING.
COOLER AIR BEGINS TO FILTER INTO THE REGION LATE MONDAY AFTERNOON.

.LONG TERM...(MONDAY NIGHT THROUGH SATURDAY)
ISSUED AT 519 AM MST SUN MAR 1 2015

THE MAIN TROUGH SHOULD CONTINUE LIFTING OUT OF THE GREAT BASIN AND
INTO EASTERN UT AND WESTERN CO MONDAY EVENING. THE GFS PLACES THE
SURFACE COLD FRONT JUST EAST OF THE CO AND UT STATE LINE WITH THE
MAIN PRECIPITATION BAND 50 MILES EITHER SIDE OF A LINE STRETCHING
FROM THE FOUR CORNERS NORTH THROUGH GRAND JUNCTION AND THEN
NORTHEAST TO ABOUT CRAIG. THE FRONT SHOULD BE EAST OF THE
CONTINENTAL DIVIDE BEFORE 06Z. THE FLOW ALOFT SHIFTS TO THE
NORTHWEST FOR THE REST OF THE NIGHT AND ANOTHER SHORTWAVE TROUGH
ROTATES THROUGH FROM THE NW TUESDAY AFTERNOON. WITH THE FRONT
AND SECOND SHORTWAVE...DECIDED TO PUSH MOST OF THE WINTER STORM
PRODUCTS THROUGH SUNSET MONDAY...WITH THE MOUNTAIN PRODUCTS NORTH
OF INTERSTATE 70 CONTINUING 16Z TUESDAY DUE TO CONTINUED
OROGRAPHIC SNOWFALL.

THE ABOVE SCENARIO IS WELL SUPPORTED BY GOOD COLD ADVECTION
PUSHING EAST THE THERMAL RIDGE THAT IS PROJECTED TO GROW NORTH
AND OVER MUCH OF THE AREA MONDAY. THIS COOLER AIR IS REINFORCED
BY THE SECOND SHORTWAVE DROPPING IN FROM THE NW. AS THIS TROUGH
MOVES THROUGH TUESDAY THE FLOW WILL SHIFT TO THE W AND NW. PRECIP
WILL FOCUS MORE IN THE NORTH AND ON OROGRAPHICALLY FAVORED SLOPES
THROUGH TUE NIGHT.

WED AND THU...DRIER NW FLOW ALOFT WILL SPREAD OVER THE AREA...THEN
FRI AND SAT ANOTHER SHORTWAVE TROUGH WILL DROP IN FROM THE NW WITH
A CHANCE OF SNOW ACROSS MAINLY THE NW PLATEAU AND THE NORTHERN
AND CENTRAL MOUNTAINS OF W. CO.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1042 AM MST SUN MAR 1 2015

WIDESPREAD LOW CLOUDS AND PRECIP WILL CONTINUE TODAY ACROSS THE
ENTIRE AREA. FLIGHT CONDITIONS WILL FLUCTUATE FROM VFR TO BELOW
IFR AS BANDS SET UP. THIS WILL OCCUR THROUGH THE DAY AND INTO THE
OVERNIGHT. CONDITIONS WILL CHANGE RAPIDLY THROUGH THE DAY FOR ALL
TAF SITES.  AFTER 06Z THIS EVENING IFR CIGS AND VSBYS IN SNOWFALL
AND FOG WILL PREVAIL AT KEGE...KASE...KTEX...KDRO...WITH OCNL MVFR
AT ALL OTHER AIRPORTS. MOUNTAINS WILL BE OBSCURED THE NEXT 24
HOURS.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER STORM WARNING UNTIL 9 AM MST WEDNESDAY FOR COZ003-013.

     WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 9 AM MST WEDNESDAY
     FOR COZ004-005.

     WINTER STORM WARNING UNTIL 5 PM MST TUESDAY FOR COZ009-010-012-
     017>019.

     WINTER WEATHER ADVISORY UNTIL 5 PM MST TUESDAY FOR COZ014.

     WINTER WEATHER ADVISORY UNTIL 8 AM MST MONDAY FOR COZ008.

     WINTER STORM WARNING UNTIL MIDNIGHT MST MONDAY NIGHT FOR
     COZ021>023.

     WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 5 PM MST TUESDAY
     FOR COZ001-002.

UT...WINTER STORM WARNING UNTIL 9 AM MST WEDNESDAY FOR UTZ025.

     WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 9 AM MST WEDNESDAY
     FOR UTZ023.

     WINTER STORM WARNING UNTIL 5 PM MST TUESDAY FOR UTZ028.

&&

$$

UPDATE...15
SHORT TERM...JAM
LONG TERM...CC
AVIATION...TGR



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