Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 271928
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
128 PM MDT MON OCT 27 2014

.SHORT TERM...(TONIGHT THROUGH TUESDAY NIGHT)
ISSUED AT 128 PM MDT MON OCT 27 2014

THIS EARLY AFTERNOON...THE LAST SNOW SHOWERS WERE LINGERING IN
SOUTHERN EAGLE COUNTY INTO THE VAIL PASS AREA. THESE WILL END
BY LATE AFTERNOON. TEMPERATURES AND DEWPOINTS ARE RUNNING 5 TO 25
DEGREES LOWER THIS AFTERNOON COMPARED TO SUNDAY.

THE NEXT CHALLENGE IS OVERNIGHT LOWS THAT MAY BRING A SEASON
ENDING FROST TO THE EASTERN UTAH VALLEYS AND PORTIONS OF WESTERN
COLORADO VALLEYS WHERE A FREEZE HAS NOT YET BEEN WIDESPREAD THIS
FALL SEASON. THE 12Z GUIDANCE GENERALLY SUPPORTS WIDESPREAD
FREEZING TEMPERATURES TONIGHT. ALSO THERE IS SOME WEAK NW TO SE
SURFACE GRADIENT THAT OFTEN KEEPS DRAINAGE WINDS IN CHECK
ALLOWING FOR COLDER LOWS. THE MAIN HOPE FOR A NON-FREEZE TONIGHT
IS A WEAK WAVE THAT MAY BRING MID-HIGH CLOUD CEILINGS. THE GFS
SEEMS TO HANDLE THIS MOISTURE BETTER SHOWING OVERCAST HIGH CLOUDS
AROUND MIDNIGHT. BUT MODELS AGREE THE CLOUDS WILL THIN AND
DISSIPATE TOWARDS SUNRISE TO ALLOW A DIP IN LOW TEMPERATURES. THE
HIGHER ELEVATIONS OF THE VALLEYS MAY SEE ONLY A SHORT PERIOD NEAR
FREEZING...LIKELY AROUND SUNRISE.

OTHERWISE HIGH PRESSURE BUILDS INTO THE GREAT BASIN FROM THE WEST
TUESDAY AND TUESDAY NIGHT. INVERSIONS STAY IN PLACE OVER THE
VALLEYS FOR NEAR NORMAL LATE-OCTOBER AFTERNOON TEMPERATURES.
ANOTHER COLD NIGHT IS IN STORE TUESDAY NIGHT. WHATEVER VALLEY
LOCATIONS DO NOT GET NIPPED TONIGHT WILL BE THREATENED AGAIN
TOWARDS WEDNESDAY MORNING.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 128 PM MDT MON OCT 27 2014

AT THE BEGINNING OF THE PERIOD WE WILL SEE AN AMPLIFIED PATTERN
WITH ONE LONG WAVE LOW PRESSURE TROUGH OFF THE WEST COAST AND
ANOTHER OVER THE EASTERN HALF OF THE CONUS. HIGH PRESSURE WILL SIT
OVER THE DESERT SOUTHWEST WITH A RIDGE EXTENDING INTO BRITISH
COLUMBIA. A DRY NORTHWEST FLOW WILL DOMINATE EASTERN UT AND
WESTERN CO. THE WARMING TREND WILL ACCELERATE AS THE PATTERN
SHIFTS EAST THROUGH THE PERIOD WITH THE RIDGE PASSING OVER THE
CENTRAL ROCKIES THURSDAY NIGHT. A SOUTHWEST FLOW WILL DEVELOP ON
FRIDAY AS THE THERMAL RIDGE PASSES OVERHEAD. THIS WILL RESULT IN
TEMPERATURES 10+ DEGREES ABOVE NORMAL ON FRIDAY FOR THE WARMEST
DAY OF THE WORK WEEK.

THE WESTERN TROUGH WILL COME ONSHORE FRI NIGHT...AND WITH AN
ASSOCIATED COLD FRONT WILL MOVE ACROSS THE GREAT BASIN ON
SATURDAY. MODEL AGREEMENT IS ON THE GOOD SIDE...WITH SOME
DIFFERENCES IN THE DETAILS. SOUTHWEST WINDS WILL STRENGTHEN ON
SATURDAY AHEAD OF THIS STORM SYSTEM. A 100KT SW-NE ORIENTED UPPER
JET MAXIMA WILL NOSE INTO THE AREA ON SAT ADDING GOOD UPPER LEVEL
SUPPORT TO THE LOW LEVEL COLD FRONT. THE ECMWF IS MORE AGGRESSIVE
IN THE SURFACE FEATURES SHOWING A VIGOROUS N-S ORIENTED SURFACE
FRONT PUSHING ACROSS THE AREA LATE SAT AFTERNOON THROUGH THE
EVENING. ALSO MODELS SHOW THIS TROUGH WILL BE THE COLDEST ONE SO
FAR THIS SEASON...WITH COLD CORE OF -26C AT 500 MB MOVING OVER OUR
FORECAST AREA BEHIND THE TROUGH AXIS. SNOW LEVELS WILL FALL QUITE
LOW AS 700MB TEMPS DIP TO -8C. THE NORTHERN COLORADO MOUNTAINS
WILL BE FAVORED... EXTENDING INTO THE CENTRAL DIVIDE AREA. FOR NOW
MOISTURE STILL MIGHT BE THE LIMITING FACTOR.

TEMPERATURES WILL DROP ON SAT DUE TO THE INCREASED CLOUDS...THEN
EXPECT MUCH COOLER TEMPS ON SUN AS THEY FALL BELOW NORMAL. VERY
CHILLY MORNING LOWS ARE EXPECTED ON MONDAY ONCE THE DRIER
NORTHWEST FLOW MOVES OVER THE AREA.


&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY AFTERNOON)
ISSUED AT 128 PM MDT MON OCT 27 2014

A WEAK PASSING DISTURBANCE WILL BRING PERIODS OF MID TO HIGH
CLOUDS TONIGHT THAT WILL THIN TOWARDS MORNING. OTHERWISE VFR
CONDITIONS WILL DOMINATE THROUGH THE WORK WEEK.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...FREEZE WARNING FROM 3 AM TO 9 AM MDT TUESDAY FOR COZ006-011-020.

UT...FREEZE WARNING FROM 3 AM TO 9 AM MDT TUESDAY FOR UTZ022-024-027-
     029.

&&

$$

SHORT TERM...JOE
LONG TERM...EH
AVIATION...JOE



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