FXUS65 KGJT 231309
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
609 AM MST WED DEC 23 2009

.SHORT TERM...TODAY THROUGH THURSDAY NIGHT

OCCASIONAL SNOW FELL ACROSS MUCH OF THE FORECAST AREA LAST EVENING AS
MOIST AIR WRAPPED BACK AROUND THE UPPER LOW OVER ARIZONA. TEMPS HAVE
REMAINED NEARLY STEADY OR SLOWLY WARMED IN MANY PLACES. AREAS OF FOG
HAVE DEVELOPED EARLY THIS MORNING WITH DENSE FOG ALONG THE I-70
CORRIDOR. AS A RESULT...HAVE ISSUED A DENSE FOG ADVISORY FOR CO
ZONES 6 AND 7 AND UTAH ZONE 27 TO COVER THIS.

MAIN FORECAST CHANGES IN THE SHORT TERM WERE TO DROP THE ADVISORY FOR
UT ZONE 27 /MOAB/ AND TO INCREASE CHANCE OF SNOW FOR THE LOWER
ELEVATIONS OF NW CO TODAY AND TONIGHT. OTHERWISE...GENERALLY JUST
TWEAKED THE CURRENT FORECAST.

THE UPPER LOW WAS MOVING FROM NE AZ INTO NW NEW MEXICO AT 10Z AND
WILL CONTINUE ACROSS NRN NM TODAY. PRECIP DECREASING AS ISENTROPIC
UPGLIDE IN WRAPAROUND DIMINISHES EARLY THIS MORNING AND FLOW ALOFT
BECOMES NORTHERLY. STILL SOME CONVECTIVE BANDS MOVING N INTO SW CO
AND EXTREME SE UT AROUND THE UPPER LOW SO WILL KEEP HIGHLIGHTS
GOING THERE ALTHOUGH PRECIP SHOULD DECREASE THIS AFTERNOON...AND
WARNINGS IN THE 4-CORNERS MAY BE ABLE TO BE CANCELLED EARLY...
ESPECIALLY FOR SE UT. ONLY SCATTERED LIGHT SNOW EXPECTED FOR MOAB
AREA TODAY...SO WILL CANCEL THE ADVISORY THERE THIS MORNING.

FORECAST AREA COULD BE IN A BIT OF A PRECIPITATION LULL LATE THIS
MORNING AND AFTERNOON WITH SNOW PROBABLY DRIVEN BY LOCAL OROGRAPHIC
EFFECTS MORE THAN ANYTHING. A DISTURBANCE CURRENTLY PLUNGING SOUTH
ACROSS ALBERTA CANADA WILL IMPACT MAINLY WRN CO LATE TODAY AND
TONIGHT...AND BRING A GOOD SHOT OF COLD AIR. THIS WILL FOCUS SNOW
MAINLY ON THE NRN AND CENTRAL CO MTNS BUT ALSO THE NW SAN JUANS MTNS.
BUFKIT AND TIME-HEIGHT CHARTS SHOW NEARLY SATURATED NORTHERLY FLOW ON
THE N SIDE OF THE ROAN/TAVAPUTS/FLATTOPS...SO RAISED POPS TO LIKELY
FOR THE CRAIG/MEEKER/STEAMBOAT AREAS LATE TODAY AND TONIGHT. DAY
SHIFT CAN EVALUATE FURTHER IF AN ADVISORY IS NEEDED THERE.

AREAS SNOW COULD LINGER IN THE NRN MTNS THU-THU NIGHT IN NWLY FLOW
BUT ACCUMS NOT EXPECTED TO BE GREAT AT THIS TIME. COLD AIR WILL
AGAIN SETTLE INTO VALLEYS.

.LONG TERM...CHRISTMAS EVE THROUGH TUESDAY

COLD NORTHERLY FLOW WILL START OFF THE PERIOD AS A DEEP UPPER
LEVEL LOW DROPS SOUTH INTO THE CENTRAL U.S. LINGERING MOISTURE
NEAR THE DIVIDE WILL KEEP A FEW SNOW SHOWERS GOING OVER THE PARK
AND GORE RANGES...OTHERWISE CONDITIONS WILL BE DRY. AS THE UPPER
LOW PULLS AWAY FROM THE REGION TOWARD THE GREAT LAKES...SHRTWV
RIDGING WILL BE BUILDING IN FOR THE WEEKEND...WITH DRY...BUT
COLD CONDITIONS CONTINUING. THE RIDGE TRANSITIONS EAST BY MONDAY
WITH DEEP SOUTHERLY FLOW AGAIN DEVELOPING OVER THE FORECAST
AREA AS ANOTHER LOW SLIDES INTO SOUTHERN ARIZONA. AT THIS TIME...THIS
SYSTEM WILL BE TOO FAR SOUTH TO BRING MUCH IMPACT ON OUR AREA...WITH
ONLY A FEW SNOW SHOWERS REACHING THE SOUTHERN MOUNTAINS. STILL
PLENTY OF DISAGREEMENT BETWEEN THE GFS AND ECMWF REGARDING THIS
SYSTEM...WITH THE GFS MUCH SLOWER. SO WILL BE KEEPING POPS AT THE
MINIMAL STAGE FOR NOW...WITH SLIGHT CHANCE VALUES FOR THE SOUTHERN
MOUNTAINS FOR MONDAY AFTERNOON. TEMPS WILL REMAIN BELOW NORMAL
FOR THE VALLEYS THROUGH THE PERIOD AS STRONG INVERSIONS REDEVELOP
UNDER THE PASSING RIDGE.

&&

.AVIATION...

LOW CLOUDS AND OCCASIONAL SNOW SHOWERS WILL CONTINUE TO IMPACT
EASTERN UTAH AND WESTERN COLORADO THROUGH TONIGHT. EXPECT MVFR CIGS
AND VSBYS WITH AREAS OF OF IFR AND LIFR CONDS...ESPECIALLY OVER
SOUTHEAST UTAH AND SOUTHWEST COLORADO. CONDITIONS WILL SLOWLY IMPROVE
EARLY THURSDAY MORNING.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...WINTER WEATHER ADVISORY UNTIL 6 PM MST TODAY FOR ZONE 020.
     WINTER STORM WARNING UNTIL 6 PM MST TODAY FOR ZONES
      019-021>023.
     WINTER WEATHER ADVISORY UNTIL 6 AM MST THURSDAY FOR ZONES
      003-004-009-010-012-013-017-018.
     DENSE FOG ADVISORY UNTIL 11 AM TODAY FOR ZONES 006-007.
UT...WINTER WEATHER ADVISORY UNTIL 6 PM MST TODAY FOR ZONES
      023-025-029.
     WINTER STORM WARNING UNTIL 6 PM MST TODAY FOR ZONES 022-028.
     DENSE FOG ADVISORY UNTIL 11 AM TODAY FOR ZONE 27.

$$

SHORT TERM...JAD
LONG TERM....JDC
AVIATION.....JDC

$$