FXUS65 KGJT 012155
AFDGJT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
255 PM MST TUE DEC 1 2009
.SHORT TERM...TONIGHT THROUGH THURSDAY...
12Z MODELS AND THE FORECAST DETAILS ARE IN GOOD AGREEMENT. A
CONTINENTAL COLD TROUGH IS DROPPING S-SE OUT OF ALBERTA AND THE
NORTHERN ROCKIES BRINGING COLD AIR TO THE REGION. THIS SYSTEM IS
MOISTURE STARVED AND THE STRONGEST COLD ADVECTION AND DYNAMICAL
SUPPORT WILL OCCUR EAST OF THE CONTINENTAL DIVIDE. THE ASSOCIATED
COLD FRONT IS STRETCHED NW-SE ACROSS WYOMING AND IS STARTING DOWN THE
COLORADO FRONT RANGE THIS AFTERNOON.
TONIGHT-WEDNESDAY: THE FRONT WILL PUSH INTO NE UT-NW CO THIS
EVENING...AND SOUTH OF I-70 AROUND MIDNIGHT. THERE IS IMPRESSIVE
COLD ADVECTION BEHIND THIS FRONT WITH ABOUT 12C/22F OF COOLING
PUSHING ACROSS THE FORECAST AREA BY LATE WEDNESDAY. THE MODELS LOOK
LIKE THEY ARE UNDER-PRODUCING WIND AND SNOWFALL WITH AND BEHIND SUCH
A STRONG FRONT. SO FOR THIS FORECAST...ADVECTED THE FRONT A BIT
FASTER THAN PROGGED OVERNIGHT. ALSO BUMPED UP WIND SPEEDS AND WIND
GUSTS ESPECIALLY ON THE DOWN-WIND SOUTH-FACING SLOPES. SNOW AMOUNTS
STILL LOOK MEAGER...MAXING OUT AT AROUND 2-4 INCHES ALONG THE WEST
SLOPE OF THE CONTINENTAL DIVIDE. THE FRONT WILL PUSH SOUTH OF THE
FOUR-CORNERS WEDNESDAY AFTERNOON PRODUCING LITTLE OR NO MEASURABLE
SNOWFALL IN THE SOUTHERN MOUNTAINS.
WEDNESDAY NIGHT-THURSDAY: COLD ADVECTION COMES TO AN END WITH
TEMPERATURES AT 700/500MB AT -17/-34C ALONG THE CONTINENTAL DIVIDE.
LOW TEMPERATURES WILL PLUMMET KEPT UP ONLY BY SOME GRADIENT WIND
AND MID-LEVEL MOISTURE. SNOW SHOWERS WILL END EXCEPT PERHAPS IN THE
EASTERN MOUNTAINS. INSTABILITY SHOWERS THURSDAY AFTERNOON COULD
PRODUCE A FEW INCHES OF HIGHER MOUNTAIN ACCUMULATION.
.LONG TERM...THURSDAY NIGHT THROUGH TUESDAY...
A FEW FLURRIES MAY LINGER OVER THE NORTHERN CONTINENTAL DIVIDE
THURSDAY NIGHT IN THE NORTHWEST FLOW. HOWEVER A MUCH DRIER AIR MASS
WILL MOVE OVER THE AREA AND WILL ALLOW EXCELLENT RADIATIONAL COOLING
OVERNIGHT. THEREFORE VERY COLD MORNING LOWS WILL BE EXPECTED WITH
MANY LOCATIONS DROPPING INTO THE SINGLE DIGITS OR EVEN BELOW ZERO
DEGREES FAHRENHEIT. THE DRY NORTHWEST FLOW WILL CONTINUE...EVENTUALLY
BECOMING ZONAL BY SATURDAY NIGHT AS THE NEXT SYSTEM MOVES INTO THE
NORTHWEST. THE COLD TEMPERATURES WILL SLOWLY MODIFY THROUGH THE
REMAINDER OF THE WEEK...BUT WILL STILL REMAIN BELOW NORMAL.
MODEL SOLUTIONS CONTINUE TO EVOLVE FOR THIS NEXT SYSTEM. IN TODAYS
12Z RUNS...LOW PRESSURE MOVES INTO THE PACIFIC NORTHWEST...THEN
CLOSES OFF OVER THE NORTHERN ROCKIES. THIS LOW THEN RETROGRADES BACK
OVER THE NORTHWEST STATES WITH AN INCREASINGLY MOIST AND SOUTHWEST
FLOW DEVELOPING OVER OUR REGION SATURDAY AND SUNDAY. THE ECMWF IS
MORE PROGRESSIVE...OPENING UP THE LOW ON MONDAY AND TAKING THE OPEN
WAVE ACROSS THE NORTHERN TIER STATES ON TUESDAY. THE GFS KEEPS THE
LOW MORE WEST/SOUTH AND CLOSED...DROPPING IT INTO THE GREAT BASIN ON
TUESDAY. BOTH SOLUTIONS SHOW GOOD ISENTROPIC UPGLIDE AHEAD OF THE
LOW...WHICH WOULD BE OUR SOURCE OF LIFT FOR THE MOIST AIR MASS UNTIL
THE LOW PASSES. THE EC REALLY JUST INDICATES A BRUSH-BY ON TUESDAY.
THE GFS SHOWS A MORE DIRECT HIT...BUT BEYOND THE LONG TERM PERIOD.
HAVE MADE FEW CHANGES TO THE FORECAST. WILL KEEP THE BROAD-BRUSHED
FORECAST WITH A SLIGHT CHANCE OF PRECIPITATION DEVELOPING OVER THE
NORTH SAT NIGHT INTO SUN. CHANCES WILL THEN INCREASE SUN NIGHT INTO
MON...CONTINUING THROUGH TUE. HOWEVER THE FORECAST REMAINS UNCERTAIN
DUE TO CONTINUED MODEL EVOLUTION. WILL WAIT FOR A LITTLE BETTER
CONTINUITY BEFORE INCREASING THE POPS INTO THE LIKELY CATEGORY.
&&
.AVIATION...
VFR CONDITIONS WILL ERODE AFTER SUNSET AS A COLD FRONT PUSHES IN
FROM THE N. THE COLD FRONT SHOULD REACH A KVEL-KHDN LINE ABOUT 00Z-
03Z WED...THEN TO NEAR THE I-70 CORRIDOR INCLUDING KGJT-KRIL-KEGE
ABOUT 07-09Z. CLOUDS WILL LOWER ACROSS THE N BETWEEN 00Z-06Z
NEAR AND BEHIND THE FRONT AS MVFR/LOCALLY IFR CIGS DEVELOP IN -SN
ACROSS THE MTNS AROUND KSBS AND OVER THE FLATTOPS. THE LOWER CIGS AND
AREAS OF -SN WILL MOVE SOUTH ACROSS THE CENTRAL CO MTNS AFTER 06Z
WED AND CONTINUE THROUGH 21Z FOR KASE. KMTJ WILL ONLY SEE LOCALIZED
MVFR CONDITIONS IN LIMITED MOISTURE.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...NONE.
UT...NONE.
&&
$$
SHORT TERM...JOE
LONG TERM....EH
AVIATION.....TGJT
