FXUS65 KGJT 061047
AFDGJT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
347 AM MST SUN DEC 6 2009
...MAJOR WINTER STORM WILL CONTINUE TO IMPACT EASTERN UTAH AND
WESTERN COLORADO THROUGH TUESDAY...
.SHORT TERM...TODAY THROUGH MONDAY NIGHT
FOLLOWING THE FASTER...LESS AMPLIFIED AND MORE CONSISTENT GFS...BUT
CANNOT TOTALLY DISCOUNT THE SLOWER NAM. SO THIS DOES NOT ADD TO
FORECAST CONFIDENCE.
THE SYNOPTIC SITUATION IS...DUAL UPPER LOWS SPIN OVER SLC AND WESTERN
OREGON. THE SLC LOW PRODUCES SOME FORCING ACROSS OUR NORTHERN
ZONES TODAY. THE OREGON LOW DOMINATES STARTING TONIGHT AND DIGS INTO
NORTHERN CALIFORNIA ON MONDAY BEFORE STARTING TO PROGRESS MONDAY
NIGHT.
TODAY: CENTER OF HT FALLS PROGRESSES THRU THE SOUTHERN CWA THIS
MORNING AS THE 700MB LOW LIFTS THRU NE UT INTO WYOMING. VORT MAX AND
A SPOKE OF -32C COLD CORE OFF THE SLC LOW ROTATES THROUGH NE UT-NW CO
THIS AFTERNOON AS THE JET LIFTS INTO THE CWA. ACROSS THE NORTH...
700MB TEMPS REMAIN IN THE DENDRITIC CRYSTAL GROWTH REGION FOR
EFFICIENT SNOW PRODUCTION. MTN TOP (700-600MB) SW WINDS INCREASE TO
20KTS NORTH 30KTS SOUTH. OTHER SW-FACING SLOPES ESPECIALLY THE WEST
ELK RANGE WILL PICK UP SNOWFALL.
TONIGHT: JET LIFTS NORTH THRU THE FORECAST AREA USHERING IN DEEP
WARM ADVECTION. THIS DOES PROVIDE A SHORT-LIVED BREAK IN THE
SNOWFALL FOR MOST AREAS BEFORE THE BIG WINDS AND OROGRAPHIC SNOWFALL
STARTS MONDAY. MTN TOPS WINDS INCREASE TO 30KTS NORTH 40KTS SOUTH BY
MORNING.
MONDAY: WARM ADVECTION IN SW FLOW ALOFT. IMPRESSIVE UPGLIDE SEEN ON
THE 300-305K SFC WITH A SATURATED 30MB OF LIFT SEEN OVER THE
SOUTHERN ZONES. 700MB TEMPERATURES CLIMB TO A LESS EFFICIENT -6C
SOUTH...-10C NORTH. MTN TOP WINDS INCREASE TO 35-45KTS.
CZ14-GUNNISON BASIN LOOKS THE MOST LIKELY LOCATION FOR A SIGNIFICANT
OVERRUNNING EVENT WITH THE COLD INVERSION DIFFICULT TO ERODE THERE.
CZ4/10/13-NORTHERN MTNS WILL LIKELY SEE ONLY LIGHT SNOWFALL BUT
SIGNIFICANT BLOWING SNOW...THEREFORE WILL LEAVE THE WATCHES IN PLACE.
CZ9/12-GRAND MESA/WEST ELKS WILL BE PULLED UP TO A BLIZZARD WARNING
WITH GREATER CONFIDENCE. SNOWFALL WILL LIKELY BE LOWER ON MONDAY BUT
THE WINDS/BLOWING SNOW WILL BE THREATENING.
CZ21/22/23-SOUTHERN VALLEYS ARE ON THE RAIN-SNOW LINE. 8-7 THICKNESS
OF 153 DAM INCREASES TO 155 DAM IN THE AFTERNOON. SNOW LEVEL LOOKS TO
START AT AT 5000 FT IN THE MORNING BUT RISE TO AROUND 7000 FT IN THE
AFTERNOON. EXPECT CORTEZ TO TURN TO ALL RAIN...BUT HIGHER PORTIONS OF
THAT ZONE SUCH AS DOVE CREEK COULD STAY IN SNOW. DURANGO AND PAGOSA
TOO ARE ON THE R-S CUSP. RELUCTANTLY WILL LEAVE THESE ZONES IN
WATCHES. THE SE UTAH VALLEYS LOOK TO STAY BELOW THE RAIN-SNOW LINE.
MONDAY NIGHT: WEST-TO-EAST ORIENTED JET NOSE PUSHES INTO CENTRAL NM
PRODUCING DIVERGENCE OVER THE SOUTHERN ZONES. 700 TEMPS WARM TO -4C
OVER THE SOUTH FOR CONTINUES RAIN-SNOW LINE ISSUES IN THE SOUTHERN
VALLEYS. MTN TOP WINDS NOW INCREASE TO AROUND 55KTS SOUTH FOR DIRE
CONDITIONS ESPECIALLY IN THE SOUTHERN-CENTRAL MTNS. THE FAVORED GFS
DEVELOPS A SURFACE FRONT ALONG THE ROAN-TAVAPUTS PLATEAU AFTER
MIDNIGHT QUICKLY SHIFTING THE FLOW NORTH OF THERE TO NE. THIS STRONG
SFC CONVERGENT SIGNATURE WOULD PRODUCE HEAVY SNOWFALL FOR RANGELY-
MEEKER AND PERHAPS THE I-70 CORRIDOR. AGAIN...THE SLOWER NAM DOES NOT
PRODUCE THIS FEATURE SO WARM SW FLOW WOULD NOT PRODUCE HEAVY SNOWFALL
IN THESE AREAS.
.LONG TERM...TUESDAY THROUGH SUNDAY...
TUESDAY WILL FINALLY SEE THE FOCUS OF THE HEAVIER SNOWFALL SHIFT FROM
OUR SOUTHERN MOUNTAINS TO THE NORTHERN MOUNTAINS AS LONG WAVE TROUGH
PUSHES EAST. THIS WILL BRING WEST TO NORTHWEST FLOW ALOFT...ALONG
WITH A FEW ADDITIONAL WIGGLES IN THE FLOW...TO GET HEAVIER SNOWFALL
GOING OVER THE NORTHERN MOUNTAINS. RIGHT ENTRANCE REGION OF 80 TO
100 KT JET MAX WILL BE OVER THE NORTHERN ZONES EARLY TUESDAY TO HELP
ENHANCE LIFT. IN ADDITION...SURGE OF CAA AND CONTINUED MOIST
ENVIRONMENT WILL SUPPORT HEAVIER SNOWFALL. DUE TO THE SLIGHTLY
DELAYED ONSET OF THE HEAVIER SNOWFALL...WE HAVE OPTED TO CONTINUE
THE WINTER STORM WATCH FOR THESE AREAS FOR NOW. VALLEY SNOWFALL WILL
ALSO BE PICKING THROUGH THIS PERIOD AS FLOW BECOMES MORE FAVORABLE...
ESPECIALLY ALONG THE I-70 CORRIDOR. HAVE MADE SOME SIGNIFICANT
ADJUSTMENTS TO SNOWFALL AMOUNTS AS WE FELT WE WERE A LITTLE TOO HIGH
FOR INDIVIDUAL 12 HOUR PERIODS...SO BACKED OFF THE HEAVIER AMOUNTS
AND SPREAD THEM OVER LONGER PERIODS. IT NOW LOOKS AS THOUGH WE WILL
SEE A GRADUAL DECREASE IN SNOWFALL INTENSITY FROM WEST TO EAST
TUESDAY NIGHT AND WEDNESDAY...ALTHOUGH LOW LEVEL MOISTURE AND
FAVORABLE NORTHWEST FLOW WILL KEEP SHOWERS GOING THROUGH WEDNESDAY.
PATTERN REMAINS UNSETTLED THROUGH THE END OF THE WEEK AS THE GFS AND
ECMWF BOTH ADVERTISE ANOTHER SYSTEM MOVING THROUGH THURSDAY NIGHT
AND FRIDAY...WITH ADDITIONAL ACTIVITY EXPECTED OVER THE WEEKEND AS
MOIST WNW PATTERN CONTS. TEMPS ARE EXPECTED TO REMAIN NEAR TO
SLIGHTLY BELOW SEASONAL NORMS THROUGH THIS PERIOD.
&&
.AVIATION...
WIDESPREAD MVFR CONDS EXPECTED THROUGH THIS EVENING WITH AREAS OF
IFR/LIFR CIGS IN VSBYS AS SNOW SPREADS OVER THE REGION. A BRIEF
BREAK WILL OCCUR OVERNIGHT WITH CIGS AND VSBYS IMPROVING INTO THE
VFR CATEGORY...BUT THIS WILL BE SHORT-LIVED AS A ANOTHER STORM
SWEEPS INTO THE REGION EARLY MONDAY...WITH MVFR CIGS AND VSBYS
RETURNING WITH WIDESPREAD SNOW.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER STORM WATCH FROM MONDAY MORNING THROUGH TUESDAY
AFTERNOON FOR COZ003-004-010-013-014-021>023.
BLIZZARD WARNING FROM MONDAY MORNING THROUGH TUESDAY AFTERNOON
FOR COZ009-012-017>019.
WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 PM MST
SUNDAY FOR COZ002-004-005-010-013.
WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO MIDNIGHT MST
SUNDAY NIGHT FOR COZ012.
UT...WINTER STORM WATCH FROM MONDAY MORNING THROUGH TUESDAY
AFTERNOON FOR UTZ023-025.
BLIZZARD WARNING FROM MONDAY MORNING THROUGH TUESDAY AFTERNOON
FOR UTZ028.
WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 PM MST
SUNDAY FOR UTZ023.
&&
$$
SHORT TERM...JOE
LONG TERM....JDC
AVIATION.....TGJT
