Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 011042
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
442 AM MDT WED OCT 1 2014

.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 442 AM MDT WED OCT 1 2014

NEXT DYNAMIC SHORT WAVE HAS SPREAD SHOWERS WITH EMBEDDED
THUNDERSTORMS INTO PARTS OF EAST CENTRAL UTAH AND WEST CENTRAL
COLORADO. COMBINATION OF THE UPPER LEVEL JET ROUNDING THE BASE OF
THE TROUGH AND THE SURFACE FRONT CUTTING ACROSS NE UTAH HAS
ALLOWED PCPN AND STORMS TO BE FOCUSED OVER THE TAVAPUTS AND ROAN
PLATEAU. THE SHORT TERM MODELS SUCH AS THE HRRR AND NAMDNG25 HAVE
DEPICTED THIS TREND. ADJUSTED GRIDDED PCPN FORECAST TO REFLECT
HIGHER CONFIDENCE THAT FREQUENT SHOWERS WILL OCCUR ACROSS THIS
AREA. AS THE DAY PROGRESSES...SHOWERS CONTINUE TO EXPAND ACROSS NW
COLORADO WITH THE SRN TAIL REACHING THE WRN SAN JUAN MOUNTAINS
LATE THIS MORNING (WITH DRYING TREND ACROSS ERN UTAH). THE RAP
MODEL DOES NOT SHOW MUCH CAPE...BUT THE MID LEVEL COLD ADVECTION
HAS STEEPEN LAPSE RATES THAT THUNDERSTORMS WILL OCCUR ALONG THE
COLD FRONT. SNOW LEVELS WILL LOWER TO BELOW THE MOUNTAIN PASSES AS
THE COLD FRONT SWEEPS ACROSS THE FORECAST AREA. THE WET BULB ZERO
LINE DROPS BELOW 10K FEET WITH THE APPROACHING COLD FRONT...SO THE
IDEA THAT THE ACCUMULATING SNOWFALL WILL BE AT OR ABOVE 9K FEET
SEEMS REASONABLE. MODELS SHOW DECENT QPF VALUES FOR THE NWRN SAN
JUAN MOUNTAINS...GRAND MESA...ELKS/WEST ELKS AND MONARCH...HENCE
HAVE ELECTED TO EXPAND THE WINTER WEATHER ADVISORY ABOVE 9K FEET
FOR THESE LOCATIONS.

THIS EVENING THE NEW COLD AIR MASS CONTINUES TO POUR THROUGH THE
REGION. THE -21C COLD CORE PASSES OVER THE NORTHERN AND CENTRAL
COLORADO ZONES THROUGH MIDNIGHT. MOISTURE IS QUITE LIMITED IN THE
NEW AIR MASS ESPECIALLY OVER THE WESTERN HALF OF THE FORECAST
AREA. THE COLD ADVECTION IS STRONGEST ACROSS NW COLORADO THAT WILL
EFFICIENTLY WRING OUT ALL AVAILABLE MOISTURE. LIGHT SNOW MAY
PERSIST ALONG THE EASTERN MOST PORTION OF THE FORECAST AREA INTO
THURSDAY MORNING. ALL BUT THE LOWEST VALLEY ZONES WILL LIKELY SEE
LOW TEMPERATURES BELOW FREEZING. DEWPOINTS WILL FALL FASTER THAN
THE TEMPERATURES FOR LITTLE THREAT OF FOG...THOUGH SOME RIVER FOG
MAY OCCUR FOR A FEW HOURS INTO THURSDAY MORNING.

SKIES WILL CLEAR IN THURSDAY IN A DRY NW FLOW. TEMPERATURES WILL
REMAIN SOME 10 DEGREES BELOW NORMAL...AND NW GRADIENT WINDS WILL
MAKE IT FEEL EVEN COOLER.

.LONG TERM...(THURSDAY NIGHT THROUGH TUESDAY)
ISSUED AT 442 AM MDT WED OCT 1 2014

HIGH PRESSURE BUILDS ALONG THE CALIFORNIA COAST KEEPING THE
REGION IN A DRY NORTHWEST FLOW.

SATURDAY THROUGH TUESDAY...THE FORECAST AREA WILL BE IN BETWEEN A
STRONG SUBTROPICAL RIDGE OVER CALIFORNIA/ARIZONA AND THE MAIN
WESTERLIES WELL NORTH TO NORTHEAST OF COLORADO. DRY AND STABLE AIR
MASS MEANS DRY WEATHER THROUGH THE PERIOD. AS THE WESTERLIES
RETREAT NORTHWARD...A SLOW WARMING TREND ALLOWS TEMPS TO CLIMB
ABOVE SEASONAL NORMS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1000 PM MDT TUE SEP 30 2014

SHOWERS WILL INCREASE FROM THE NORTHWEST AFTER 12Z. NORTH OF THE
I-70 CORRIDOR 09-15Z MTNS WILL OBSCURED AT TIMES IN LOW CLOUDS AND
PRECIPITATION. KVEL KCAG KHDN KSBS ALL WILL SEE PERIODS OF VSBY
BLO 3SM CIGS BLO 030 AFTER 09Z. FOR KCNY KGJT KMTJ KTEX KRIL KASE
KEGE EXPECT DETERIORATING CIGS AFTER 15Z WITH MVFR CONDITIONS AFT
18Z OF VSBY BLO 5SM CIGS BLO 040 IN -SHRA/-TSRA. KTEX KEGE KASE
COULD ALL SEE PERIODS OF IFR VSBY BLO 3SM CIGS BLO 030 IN
-SHSN/-TSSN AFTER 21Z. KDRO WILL REMAIN VFR EXCEPT BRIEF MVFR IN
ISOLATED SHOWERS 18-23Z.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...FREEZE WATCH FROM LATE TONIGHT THROUGH THURSDAY MORNING FOR
     COZ001-002-005-014.

     WINTER WEATHER ADVISORY FROM 9 AM THIS MORNING TO MIDNIGHT MDT
     TONIGHT FOR COZ004-009-010-012-013-018.

UT...WINTER WEATHER ADVISORY UNTIL MIDNIGHT MDT TONIGHT FOR UTZ023.

&&

$$

SHORT TERM...PF/JOE
LONG TERM...JOE/PF
AVIATION...JOE


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