Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 112100
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
300 PM MDT THU SEP 11 2014

.SHORT TERM...(TONIGHT THROUGH FRIDAY NIGHT)
ISSUED AT 300 PM MDT THU SEP 11 2014

TIGHTENING PRESSURE GRADIENT OVER NW COLORADO IS PRODUCING SOME
OROGRAPHIC CLOUD AND GUSTY SURFACE WINDS TO 25 KTS. DOWNSCALED
NAMDNG25 AND RAP13 PAINTS A THIN RIBBON OF LIGHT SHOWERS FROM
BOOKCLIFFS TO THE FLAT TOPS BY LATE AFTERNOON. VISUAL SATELLITE
IMAGES DO SHOW LOW TOP CONVECTION IS FORMING OVER THE HIGHER
TERRAIN OF NW AND WC COLORADO...SO SCENARIO APPEARS TO BE IN PLAY.
ANY LIGHT SHOWERS WILL DISSIPATE WITH SUNSET.

SURFACE COLD FRONT FROM WYOMING DROPS INTO NW COLORADO EARLY THIS
EVENING AND SPREADS SOUTHWARD. APPEARS THIS FRONT REACHES THE I70
CORRIDOR LATE THIS EVENING...BUT DOES NOT GO MUCH FARTHER SOUTH.
MINIMAL MOISTURE WITH THE FRONT AND NOT EXPECTING ANY WEATHER
EXCEPT FOR A WIND SHIFT TO N-NE. DRIER AIR MASS FILTERING INTO NW
COLORADO WILL ALLOW TEMPS TO FALL BELOW FREEZING ALONG THE RIVER
VALLEYS AND LOW LYING SPOTS. CONFIDENCE IS HIGH THIS WILL OCCUR
WITH MID TO UPPER 20S IN THE YAMPA AND WHITE RIVER BASINS. WILL
UPGRADE THE FREEZE WATCH TO FREEZE WARNING AND INCLUDE STEAMBOAT
SPRINGS VICINITY.

GRADIENT FLOW RELAXES ON FRIDAY AS COLD TROUGH MOVES ACROSS THE
CENTRAL PLAINS. AIR MASS WILL BE SIGNIFICANTLY DRIER AND WILL MEAN
MORE SUNSHINE FOR THE ENTIRE REGION. COOLER MAX TEMPS ACROSS THE
NORTH...BUT NEAR PERSISTENCE FOR THE SOUTHERN HALF.

INTERESTINGLY MODEL DATA SHOWS A LITTLE MOISTURE FILTERING INTO
ARCHULETA COUNTY ON FRIDAY NIGHT. NOT CONVINCED THAT LIGHT PCPN
WILL FORM DURING THE NOCTURNAL HOURS...WILL KEEP THE DRY FORECAST
ONGOING. IF NOTHING ELSE...SOME SHALLOW UPSLOPE FLOW MAY PRODUCE
SCATTERED CLOUDS. OTHERWISE BENIGN WEATHER CONDITIONS PERSIST
THROUGH FRIDAY NIGHT.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 300 PM MDT THU SEP 11 2014

THE LAST IN A SERIES OF TROUGHS WORKS THROUGH THE NORTHERN TIER OF
STATES ON SATURDAY. THIS ALLOWS THE SUBTROPICAL HIGH...THAT HAS
BEEN SQUASHED ALONG THE GULF COAST STATES...TO BEGIN TO AMPLIFY
WESTWARD INTO THE DESERT SW. DAYTIME TEMPERATURES REBOUND TO NEAR
NORMAL AFTER FRIDAY/S COOL DOWN. ALSO MOISTURE WILL BEGIN TO
PERCOLATE NORTH THROUGH AZ-NM INTO THIS FORECAST AREA. MARGINAL
MOISTURE OVER THE WEEKEND WILL PRODUCE MAINLY AFTERNOON MOUNTAIN
THUNDERSTORMS PRODUCING MORE WIND THAN RAIN.

MOISTURE INCREASES EARLY NEXT WEEK AS HIGH PRESSURE AMPLIFIES
NORTHWARD ALONG THE SPINE OF THE ROCKIES. NO ORGANIZED FORCING
SEEN FOR NOW...SO EXPECT SCATTERED AFTERNOON TO EARLY EVENING
STORMS AND SOME CHANCE OF LOCALLY HEAVIER SHOWERS DUE TO SLOW
STORM MOTION.

FOR WEDNESDAY INTO THURSDAY WE ARE WATCHING TROPICAL STORM ODILE
THAT MAY MAKE HURRICANE STATUS AS IT WORKS ITS WAY UP ALONG THE
MEXICAN WEST COAST. THE MORE PROGRESSIVE GFS PULLS ODILE MOISTURE
INTO THE REGION AS A PACIFIC TROUGH SWEEPS THE WEST. THE EC KEEPS
THE ROCKIES RIDGE IN PLACE WHICH FORCES ODILE OUT TO SEA.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1136 AM MDT THU SEP 11 2014

VFR WILL CONTINUE THROUGH THE FORECAST PERIOD. ISOLD -SHRA IS
EXPECTED NORTH OF THE I70 CORRIDOR FROM KRIL-KEGE AND THE WEST
CENTRAL MOUNTAINS FROM 20Z-02Z TODAY. LOCAL SURFACE GUSTS TO 25KTS
WILL BE POSSIBLE AT ALL AIRFIELDS OVER NE UTAH AND NW
COLORADO...RESULTING IN SOME MECHANICAL CHOP.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...FREEZE WARNING FROM 2 AM TO 9 AM MDT FRIDAY FOR COZ002-005.

UT...NONE.
&&

$$

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



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