Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 311737 AAA
AFDGJT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1137 AM MDT SUN AUG 31 2014

.UPDATE...
ISSUED AT 944 AM MDT SUN AUG 31 2014

FORECAST TRENDS ARE GENERALLY ON TRACK. UPPER LEVEL TROUGH AXIS
CURRENTLY MOVING OVER COLORADO. FRONTAL BOUNDARY ROUGHLY JUST
NORTH OF THE I-70 CORRIDOR. LEFT EXIT REGION OF UPPER JET IS
NOSING OVER NORTHERN CO. ALL OF THESE FEATURES CONTRIBUTING TO THE
ONGOING SCATTERED TO NUMEROUS SHOWERS/TSTMS OVER NRN CO. SATELLITE
IMAGERY DOES SHOW DRIER AIR WORKING IN FROM THE WEST. SO EXPECT
COVERAGE OF SHOWERS TO WIND DOWN AFTER EARLY AFTERNOON...AND
LIMITED MAINLY TO NRN COLORADO AND ALONG THE DIVIDE. HAVE UPDATED
FORECAST TO REFLECT THIS.

&&

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 434 AM MDT SUN AUG 31 2014

WATERVAPOR SATELLITE EARLY THIS MORNING SHOWED A NICE SHORTWAVE
TROUGH ROTATING THROUGH EASTERN ID AND WEST WY...WITH A WEAK TROP
UNDULATION AND A MODERATE JET STREAM INDICATED OVER THE
NV...ID...UT TRIPLE POINT. THE FRONT EXIT REGION OF THE JET MAXIMA
IS RIDING OVER NE UT...NW CO...AND SOUTHERN WY...ALONG WITH UPPER
DIVERGENCE AND SOME SPEED SHEAR. BENEATH THESE FEATURES SCATTERED
SHOWERS AND THUNDERSTORMS WILL CONTINUE TO MOVE THROUGH NW CO
THROUGH THIS MORNING. AS THE BETTER DYNAMICS MOVES EAST OF THE
AREA...AREAL COVERAGE WILL BEGIN SLOWLY DECREASING LATE THIS
AFTERNOON INTO THIS EVENING. HAVE INCREASED AREAL COVERAGE OF
SHOWERS AND TSTMS OVER NW AND CENTRAL CO TODAY... TAILING OFF
APPROACHING SUNSET.

TONIGHT AND MONDAY...NORTHWEST FLOW WILL BE MOVING OVER OUR NECK OF
THE WOODS OVERNIGHT AS THE TROUGH AXIS WORKS EAST OF THE ROCKIES.
LOOKING AT DERIVED GOES IMAGERY AND RAOB PWAT PLOTS...VERY DRY AIR
WILL ADVECTING INTO OUR CWA WITH PWAT DROPPING TO UNDER HALF OF AN
INCH MID DAY MONDAY. THIS IS A QUARTER OF AN INCH BELOW NORMAL WHICH
WILL SIGNAL A RETURN TO LARGER DIURNAL TEMPERATURE SWINGS THROUGH
THE WEEK. COOLER AIR INITIALLY FILTERING IN ON THE NORTHERLY FLOW
WILL LEAVE HIGHS CLOSER OR SLIGHTLY COOLER THAN NORMAL FOR MONDAY.

.LONG TERM...(MONDAY NIGHT THROUGH SATURDAY)
ISSUED AT 434 AM MDT SUN AUG 31 2014

MONDAY NIGHT AND TUESDAY...THE UPPER FLOW BE BACKING DURING THIS
TIME PERIOD...LEAVING ZONAL FLOW IN PLACE AS THE SUBTROPICAL RIDGE
IS SQUASHED ACROSS THE SOUTHERN STATES AND THE POLAR JET FLIES ALONG
THE CANADIAN/US BORDER. TEMPERATURES WILL BEGIN TO REBOUND TO
ABOVE NORMAL ON TUESDAY AS WESTERLY FLOW IS ESTABLISHED. DEEP
MIXING WILL MOST LIKELY LEAD TO SOME GUSTY AFTERNOON CONDITIONS.

TUESDAY NIGHT THROUGH WEDNESDAY NIGHT...THE SUBTROPICAL HIGH
DOMINATES THE SW U.S. WITH WEAK DRY WESTERN FLOW ALOFT OVER THE
FORECAST AREA TUE NIGHT THROUGH WED. CONDITIONS SHOULD REMAIN DRY
AND WARMER THAN NORMAL.

THURSDAY THROUGH SATURDAY...THE GFS AND ECMWF ARE COMING INTO
BETTER AGREEMENT BY INITIATING ANOTHER MONSOONAL SURGE THURSDAY
AND STRENGTHENING IT FRIDAY AND FRIDAY NIGHT. THE NEXT PACIFIC
TROUGH IS PROJECTED TO DEEPEN OFF THE WEST COAST AND SLIDE EAST ON
FRIDAY. THIS PUSHES THE SUBTROPICAL HIGH TO THE SOUTHEAST AND
OPENS UP THE FOUR CORNERS STATES TO THE NEXT MONSOONAL PLUME AS
WINDS ALOFT SHIFT TO THE SOUTHWEST. HAVE INCREASED POPS AND SKY
COVER BEGINNING THURSDAY...AS HAVE NEIGHBORING OFFICES. AT THIS
TIME IT LOOKS LIKE LATE FRI AFTERNOON AND FRIDAY NIGHT STAND THE
BEST CHANCE OF PCPN...BUT THE PARTICULARS ARE HARD TO PREDICT THAT
FAR IN THE FUTURE. THE THE GFS CONTINUING WITH DECENTLY HIGH PCPN
CHANCES SATURDAY. MODEL DIFFERENCES SHOW UP IN THE FRI AND SAT
TIMEFRAME...AS THE ECMWF PLACES THE BEST MOISTURE AND PCPN CHANCE
EAST OF THE CONTINENTAL DIVIDE...SO THE FORECAST FOR THE END OF
THE WEEK REMAIN A BIT UNCERTAIN.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1137 AM MDT SUN AUG 31 2014

VFR CONDITIONS EXPECTED THROUGH THE PERIOD. LEFT VCSH IN THE
FORECAST AT KEGE AND KASE FOR SHRA THAT MAY REDEVELOP THIS AFTN.
HOWEVER...MAIN INGREDIENTS FOR SHRA PRODUCTION ARE MOVING EAST OF
THE DIVIDE. OTHER THAN THAT...THE FORECAST CHALLENGE IS THE WIND.
DEEPER MIXING TODAY IN THE WAKE OF UPPER LEVEL TROUGH PASSAGE WILL
KICK UP WINDS THROUGH SUNSET. GUSTS NEAR 30KT POSSIBLE.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...NONE.
UT...NONE.
&&

$$

UPDATE...BEN
SHORT TERM...CC/15
LONG TERM...15/CC
AVIATION...BEN


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