FXUS65 KGJT 221726 AAA
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1026 AM MST TUE DEC 22 2009

.UPDATE...FAIRLY IMPRESSIVE RETURNS ON THE WSR-88D THIS MORNING AS
FAR AS SNOWFALL IS CONCERNED...WITH ECHOES BEING DETECTED OVER FAR
SOUTHEAST UTAH. THIS IS INDICATIVE OF HEAVIER SNOWFALL...WITH
SURFACE REPORTS CONFIRMING RADAR RETURNS. REPORTS OF OVER 8 INCHES
OF SNOW ALREADY RECEIVED NEAR THE VALLEY OF THE GODS IN SOUTHEAST
UTAH...WITH HEAVY SNOW FALLING AT SEVERAL OTHER LOCATIONS AS WELL.
LITTLE CHANGE IS EXPECTED IN THIS PATTERN THROUGH LATE THIS
AFTERNOON. AS A RESULT...HAVE MADE SOME ADJUSTMENTS TO THE CURRENT
WINTER HIGHLIGHTS INCLUDING UPGRADING THE ABAJO MOUNTAINS AND THE
EXTREME SOUTHWEST PORTIONS OF COLORADO TO WINTER STORM WARNINGS. HAVE
ALSO EXPANDED WINTER WEATHER ADVISORIES TO THE CANYONLANDS REGION AND
ALSO THE PARADOX VALLEY AND LOWER DOLORES RIVER VALLEY. ADDITIONAL
DETAILS ON THIS STORM FOUND IN THE SHORT TERM DISCUSSION BELOW.

&&

/PREVIOUS DISCUSSION... /ISSUES 226 AM MST TUE DEC 22 2009/

.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT...
BASED ON CONSISTENCY OF EVENING/EARLY MORNING MODEL RUNS WITH
PREVIOUS RUNS...DECIDED TO UPGRADE ADVISORIES TO WINTER STORM
WARNINGS SW SAN JUAN MOUNTAINS...DURANGO AREA...PAGOSA SPRINGS AREA.
ALSO ISSUING A WINTER STORM WARNING FOR EXTREME SE UTAH ABOVE 5000
FOOT LEVEL...MAINLY BLANDING AREA. OTHERWISE CLOSED UPPER LOW OVER
NRN OR DROPS RAPIDLY SOUTHWARD TO AROUND LAS VEGAS BY THIS EVENING.
ALL MODELS INDICATE SUBSTANTIAL QPF/SNOW DESPITE RATHER LACK LUSTER
FORCING...BUT ITS HARD TO IGNORE THE CONSISTENCY DISPLAYED BY
SEVERAL MDL RUNS. FOCUS OF PCPN MAINLY OVER THE SRN ZONES AS
COMBINATION OF OROGRAPHICS AND DIVERGENCE/DIFFLUENCE ALOFT WORK ON
INCREASING MSTR SUPPLY.

THE UPPER LOW SINKS INTO AZ TONIGHT AND THEN BEGINS TO MOVE
EASTWARD INTO NM. SOUTHERN ZONES REMAIN UNDER THE GUN WHILE WRAP
AROUND STARTS TO DEVELOP ACROSS THE NRN AND CNTRL MTNS BRINGING SUB
ADVISORY SNOW AMOUNTS. PCPN WILL BEGIN TO TAPER OFF ACROSS
THE SOUTH WEDNESDAY AS THE FLOW BECOMES NRLY AND FOCUS OF PCPN
SHIFTS TO THE NRN AND CNTRL MTNS. BY WEDNESDAY NIGHT THE GFS AND
ECMWF SHOW A SECONDARY WAVE HEADING FOR THE FORECAST AREA. THIS WILL
BRING A SURFACE COLD FRONT INTO THE REGION ...PROVIDING INSTABILITY
AND H7 FLOW OF 30 KTS OVER THE NORTH PROVIDING GOOD OROGRAPHIC
FORCING FOR ADDITIONAL SNOW ACCUMULATIONS.

.LONG TERM...THURSDAY THROUGH MONDAY NIGHT...
CLOSED LOW WILL BE OVR KS BY THUR AS WRAPAROUND MOISTURE AND
NRLY WIND FLOW KEEPS SNOW CHCS THRU FRI MORNING ESPECIALLY NRN AND
TO SOME DEGREE CEN MTNS DUE TO FAVORABLE OROGRAPHICS.  MODERATE
ACCUMULATIONS OF UP TO 6 INCHES ARE POSSIBLE AFTER ALL IS SAID AND
DONE...ESPECIALLY NRN MTNS.  BY THUR NIGHT...ANOTHER IMPULSE WILL
HAVE DROP DOWN FROM THE N REINFORCING THE COLD AIR ALREADY IN PLACE.
ALMOST NO PRECIP ASSOD WITH THIS PIECE OF ENERGY HOWEVER SO TOOK OUT
ALMOST ALL MENTION OF SNOW FROM FORECAST THOUGH SOME VERY ISOLD
SNOW SHOWERS ARE POSSIBLE NEAR GORE/PARK RIDGE MTNS.

FOR FRI AND SAT...WEAK RIDGING BUILDS IN AS SKIES CLEAR WHILE TEMPS
REMAIN BELOW NORMAL FRI DUE TO SECOND SHOT OF ENERGY.  BY SAT
HOWEVER...TEMPS WILL ALREADY START TO REBOUND.  DO ANTICIPATE
COLD AIR TO STICK AROUND THE VALLEYS AS INVERSIONS ONCE AGAIN SET UP
OVER REGION.  BY SUNDAY...SHEARED RIDGE AXIS WILL BE OVR CWA AS WINDS
BECOME MORE SLY AS WARM ADVECTION KICKS IN. AS THIS HAPPENS...
NEXT SHORTWAVE WILL UNDERCUT RIDGE CAUSING VERY SLIM CHC FOR PRECIP
OVR SRN CO AREAS MONDAY.

&&

.AVIATION...
PATCHY FOG AND HAZE WILL CONTINUE TO IMPACT THE KGJT AND KVEL
AIRPORTS THROUGH LATE THIS AFTERNOON. ELSEWHERE...AREAS OF SNOW WILL
BRING WIDESPREAD MVFR CIGS AND VSBYS...WITH AREAS OF IFR AND LIFR
CONDS EXPECTED...ESPECIALLY OVER SOUTHEAST UTAH AND SOUTHWEST
COLORADO. CONDITIONS WILL SLOWLY IMPROVE FROM WEST TO EAST LATE
WEDNESDAY AFTERNOON.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...WINTER STORM WARNING UNTIL 6 PM MST WEDNESDAY FOR THE SOUTHWEST
      SAN JUAN MOUNTAINS AND THE VALLEYS OF SOUTHWEST COLORADO...
      INCLUDING COZ019-021>023.
     WINTER WEATHER ADVISORY UNTIL 6 PM MST WEDNESDAY FOR THE
      NORTHWEST SAN JUAN MOUNTAINS AND THE PARADOX VALLEY AND LOWER
      DOLORES RIVER VALLEY...INCLUDING COZ018-020.
UT...WINTER STORM WARNING UNTIL 6 PM MST WEDNESDAY FOR THE ABAJO
      MOUNTAINS AND LOWER ELEVATIONS OF SOUTHEAST UTAH...INCLUDING
      ZONES UTZ022-028.
     WINTER WEATHER ADVISORY UNTIL 6 PM MST WEDNESDAY FOR CANYONLANDS
      AND NATURAL BRIDGES...INCLUDING UTZ029.

$$

UPDATE.......JDC
SHORT TERM...MC
LONG TERM....TGR
AVIATION.....JDC

$$