Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 212105
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
305 PM MDT THU AUG 21 2014

.SHORT TERM...(TONIGHT THROUGH FRIDAY NIGHT)
ISSUED AT 305 PM MDT THU AUG 21 2014

AN UPPER CLOSED LOW OVER SOUTHERN CA CONTINUES TO DIRECT MID AND
UPPER LEVEL MOISTURE AND CLOUDS OVER THE AREA...COMBINING
MOISTURE FROM TROPICAL STORM LOWELL AND THE NORMAL MONSOONAL
PLUME. THIS CLOUD COVER HELD DOWN CONVECTION TODAY AND WILL
CONTINUE TO DO SO OVERNIGHT. THE ONLY STORM DEVELOPMENT HAS
OCCURRED ON THE PERIPHERY OF THE HIGHER CLOUD COVER...OVER NE UTAH
AND NW CO. SOME CHANGES ARE EXPECTED LATE TONIGHT.

A SHORTWAVE WILL EJECT OUT OF THE CA LOW AS IT MOVES EAST TO SW
AZ LATE TONIGHT AND FRI MORNING. THIS MOISTURE SHOULD SPREAD
PRECIP INTO THE FOUR CORNERS BETWEEN 06Z AND 09Z...AND THEN PUSH
IT FURTHER NORTH INTO CENTRAL CO BY SUNRISE FRIDAY. THE NAM12
SHOWS THE LOW CENTER FILLING AND MOVING OVER THE FOUR CORNERS AS
AN OPEN WAVE FRIDAY AFTERNOON. PRECIP COVERAGE SHOULD INCREASE
THROUGHOUT THE DAY...WITH STRONG CONVECTION POSSIBLE OVER NE UT AND
NW CO WHICH WILL EXPERIENCE MORE SHEAR ALOFT AND LIFT FROM AN
APPROACHING PAC NW TROUGH. FRIDAY NIGHT THE TROUGH APPROACHING
FROM THE NW BECOMES THE DOMINANT FEATURE WITH A SIGNIFICANT BAND
OF PRECIP POSSIBLY FORMING OVER NE UTAH AFTER 06Z.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 305 PM MDT THU AUG 21 2014

SATURDAY WILL BE AN ACTIVE DAY FOR NORTHERN UTAH AND COLORADO. AN
UPPER LEVEL SHORTWAVE COUPLED WITH A 70 KT JET STREAK WILL PASS
EAST ACROSS THE WY/UT/CO BORDER THROUGH MIDDAY. THE LATEST MODELS
BRING THE MAIN AREA OF PRECIPITATION TO THE UT/CO BORDER AROUND
11AM ON SATURDAY...REACHING AS FAR SOUTH AS MOAB. SHOWERS AND
THUNDERSTORMS WILL BE FAST MOVING AND PRECIPITABLE WATER WILL NOT
SEASONABLY ABNORMAL...SO AM NOT ANTICIPATING ANY FLOODING ISSUES.
THUNDERSTORMS ARE EXPECTED TO CROP UP SOUTH OF THE MAIN PERIPHERY
OF CLOUD COVER AS WELL AS A FEW EMBEDDED THUNDERSTORMS IN THE MAIN
AREA OF PRECIPITATION.

SUNDAY...CONVECTIVE ACTIVITY WILL REMAIN MAINLY ALONG THE DIVIDE
MOUNTAINS OF A SCATTERED NATURE. THE LONGWAVE PRESSURE GRADIENT
WILL BECOME VERY LIGHT BY MONDAY WHICH WILL CUT OFF THE MOISTURE
TAP TO THE REGION. ANOTHER TROUGH SWIPES BY THE NORTHERN PART OF
OUR CWA ON MONDAY NIGHT AND TUESDAY...BUT PWATS ARE FORECAST TO BE
LESS THAN ONE HALF INCH BY WEDNESDAY WHICH REALLY PUTS A DAMPER ON
THE POTENTIAL FOR ANY SIGNIFICANT SHOWERS OR THUNDERSTORMS. THE
WY/UT/CO BORDER WILL AGAIN BE IN THE HIGHEST POPS FOR THIS TROUGH
ON TUESDAY...THOUGH AT THIS TIME LESS PRECIPITATION COVERAGE IS
EXPECTED.

BOTH 12Z MODELS SUGGEST HIGH PRESSURE BUILDING OVER THE WESTERN US ON
WEDNESDAY. THIS IS A NEW SOLUTION FOR THE EC...BUT THE GFS HOLDS
STRONG TO THIS PATTERN CHANGE BY THE END OF THE WEEK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1049 AM MDT THU AUG 21 2014

DRIER AIR AT LOWER LEVELS WILL CONTINUE TO MOVE INTO THE FORECAST
AREA THE REST OF TODAY AND TONIGHT...LIMITING THUNDERSTORM
DEVELOPMENT TO MAINLY THE CENTRAL COLORADO MOUNTAINS AND EASTERN
UINTA MOUNTAINS. AS A RESULT...EXCEPT FOR GUSTY OUTFLOW WINDS...
ITS UNLIKELY THAT TAF SITES WILL EXPERIENCE THUNDERSTORMS DIRECTLY
OVER THEIR AIRPORT COMPLEXES.

STORMS WILL LARGELY DISSIPATE BY MIDNIGHT. HOWEVER...A SURGE OF
MOISTURE...SOME OF WHICH ORIGINATES FROM TROPICAL STORM LOWELL...
WILL SWEEP INTO THE FOUR CORNERS REGION LATE TONIGHT GENERATING
NOCTURNAL SHOWERS AND THUNDERSTORMS. THERE IS A SLIGHT CHANCE THIS
ACTIVITY COULD IMPACT KTEX OR KDRO BEFORE 12Z/FRI.


&&

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

$$

SHORT TERM...CC
LONG TERM...JAM
AVIATION...CC


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