FXUS65 KGJT 251101
AFDGJT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
401 AM MST FRI DEC 25 2009
.SHORT TERM...TODAY THROUGH SATURDAY NIGHT
SATELLITE PICTURES INDICATED AN UPPER LOW DROPPING S ACROSS WRN
NEBRASKA EARLY THIS MORNING WITH ANOTHER LOW MOVING NE ACROSS SE
MISSOURI. THESE LOWS WILL DUMBBELL AND EVENTUALLY MERGE AS ONE LOW
OVER MO/IA/IL BY FRI NIGHT. THIS WILL RESULT IN NORTHERLY FLOW ACROSS
OUR FORECAST AREA TODAY INTO THE WEEKEND...AND PERSISTENT SNOW FOR
OUR NRN AND CENTRAL MTNS OF CO. A WINTER WEATHER ADVISORY FOR SNOW
AND BLOWING SNOW IS CURRENTLY IN PLACE FOR THE ELKHEAD/PARK/GORE/
FLATTOPS/ELK MTNS...AND WILL NOT BE MAKING ANY CHANGES TO IT.
SATELLITE ALSO INDICATED A SMALLER SHORTWAVE DROPPING S ACROSS
ERN UT/WRN CO AT 10Z EARLY THIS MORNING. THIS BRINGING MAINLY MID-
LEVEL CLOUDS AS IT TRAVERSES THE REGION BUT IS ALSO GENERATING AREAS
OF LIGHT SNOW NEARER THE DIVIDE...WITH ASPEN AND LEADVILLE REPORTING
LIGHT SNOW AT TIMES. WEAK Q-FORCING AND SOME MOIST ISENTROPIC UPGLIDE
INDICATED ACROSS THE FAR N LATER TODAY AND TONIGHT AS THOSE CENTRAL
U.S. LOWS CONSOLIDATE AND EMBEDDED DISTURBANCES AND MOISTURE WRAP
BACK WESTWARD. BUT...AM COUNTING MAINLY ON THE PERSISTENT NORTHERLY
OROGRAPHIC FLOW FOR MOST OF THE LIFT...WITH AIR TEMPS IN THE
FAVORABLE SNOW GROWTH REGION MAKING THE MOST OF THE AVAILABLE
MOISTURE. NORTHERN SIDE OF GRAND MESA MAY ALSO BE FAVORED IN THIS
FLOW FOR POSSIBLE ACCUMS. PRECIP LIKELY TO CONTINUE INTO SATURDAY FOR
THE NRN MTNS BUT ON A DECREASING TREND.
ACCOMPANYING THE SNOW WILL SOME NW-N WINDS AS WE WILL BE BETWEEN HIGH
PRESSURE TO OUR NW AND THE CENTRAL U.S. LOW TO OUR EAST. BESIDES
AREAS OF BLOWING SNOW OVER THE HIGHER TERRAIN...WIND CHILLS WILL BE
QUITE LOW IN THE MTNS.
COLD AIR TO BE ACROSS THE REGION AND POOLING IN VALLEYS. WHERE SKIES
ARE MOSTLY CLEAR WITH SNOW ON THE GROUND...EXPECT RADIATIONAL
COOLING TO HELP DROP NIGHTTIME NIGHTS WELL BELOW NORMAL.
.LONG TERM...SUNDAY THROUGH THURSDAY...
AFTER A PERIOD OF WELL DEFINED HIGH AMPLITUDE FEATURES...THE MODELS
FORESEE A FEW DAYS OF LESS DISTINCT PATTERNS. ON SUNDAY EASTERN UT
AND WESTERN CO ARE BENEATH THE LAST OF A SERIES OF VORT LOBES
ROTATING AROUND THE HUGE MIDWEST LOW...WHICH IS INTERACTING WITH A
DEFORMATION ZONE OVER THE SOUTHERN HALF OF THE AREA. THE OROGRAPHIC
FLOW IS WEAK. IT APPEARS THAT MID-LEVEL CLOUDS WILL BE NUMEROUS...
THOUGH THE EC INDICATES LESS CLOUD SOUTH OF ABOUT MONTROSE. HAVE IN
GENERAL INCREASED CLOUDS ACROSS THE BORDER AS THE GFS SHOWS.
MONDAY AND TUESDAY...THE GFS CONTINUES TO PRODUCE MORE MID AND HI
LEVEL CLOUD COVER WHILE MAINTAINING A MIX OF DEFORMATION OVER THE
SOUTH AND WEAK UPPER TROUGHS OVER THE NORTH. THE EC PUTS MUCH MORE
EMPHASIS ON A TROUGH OVER BAJA CA MON AND MOVES IT TO AZ AND NM
TUESDAY. THE GFS CLOSES OFF THIS TROUGH AND MOVES IT MORE SLOWLY
EAST AND MUCH FURTHER SOUTH. BELIEVE THE NET RESULT FOR BOTH
SOLUTIONS WILL BE LESS CLOUD MONDAY WITH MORE CLOUD COVER ON TUESDAY.
HAVE LEFT POPS LOW...BUT WITH A SLIGHT UPTICK TUESDAY.
AFTER THE TROUGH PASSES TO OUR SOUTH...NORTHWEST FLOW WILL AGAIN SET
UP AS HIGH PRESSURE BUILDS OVER THE WEST COAST. THIS WILL ALLOW THE
POSSIBILITY OF LIGHT OROGRAPHIC SHOWERS OVER THE FAVORED NORTHERN
SLOPES AS EMBEDDED WAVES PASS IN THE FLOW.
TEMPS WILL BE QUITE COLD AT THE BEGINNING OF THE PERIOD...THEN MODIFY
AS THE PATTERN SHIFTS EAST. THE FIRST TO WARM WILL BE THE HIGHER
ELEVATIONS. COLD AIR WILL STAY TRAPPED IN THE WESTERN VALLEYS...
ESPECIALLY CENTRAL AND NORTH...GRADUALLY WARMING TOWARDS THE END OF
THE PERIOD.
&&
.AVIATION...
AREAS OF SNOW SHOWERS WILL PERSIST OVER THE COLORADO NORTHERN AND
CENTRAL MOUNTAINS TODAY CAUSING AREAS OF MVFR CIGS AND VSBYS...
PARTICULARLY IN THE HIGH PASSES AND AT ASE
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER WEATHER ADVISORY FROM 6 AM TODAY TO 6 AM SATURDAY FOR
PORTIONS OF THE NORTHERN AND CENTRAL MOUNTAINS...ZONE 4/10/13.
UT...NONE.
$$
SHORT TERM...JAD
LONG TERM....CJC/EH
AVIATION.....CJC
$$
