Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 260517
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1117 PM MDT MON AUG 25 2014

.UPDATE...
ISSUED AT 905 PM MDT MON AUG 25 2014

MOISTURE SURGE FROM THE SOUTH OCCURS LATE TONIGHT FROM THE SOUTH
AND SPREADS NORTHWARD DURING THE DAY. MOISTURE GETS ENTRAINED FROM
AN UNUSUALLY STRONG GREAT BASIN TROUGH. DECENT MOISTURE SURGE
COMBINES WITH SYNOPTIC SCALE ASCENT AND DIVERGENCE ALOFT. THIS ALLOWS
FOR THE FORMATION OF SOME STRONG ORGANIZED CONVECTION. LOCALIZED
HEAVY RAINERS WILL OCCUR WITH THE POTENTIAL OF GENERATING ONE TO
TWO INCH RAINFALL RATES. TO COINCIDE WITH WPC GUIDANCE (SLIGHT
RISK OF EXCESSIVE RAINFALL OVER ARCHULETA AND HINSDALE COUNTY)...WILL
HOIST A FLASH FLOOD WATCH FOR THE FAR SWRN COLORADO VALLEYS AND
SAN JUAN MOUNTAINS.

&&

.SHORT TERM...(TONIGHT THROUGH TUESDAY NIGHT)
ISSUED AT 315 PM MDT MON AUG 25 2014

SOMEWHAT TRICKY FORECAST THIS AFTERNOON AS AN UPPER LEVEL JET
STREAK CONTINUES TO RIDE OVER THE FORECAST AREA. WATER VAPOR IMAGE
ALONG WITH 320K ISENTROPIC SFC CONTINUES TO SHOW MOISTURE
ADVECTING BOTH OFF THE PACIFIC COAST AND ALSO FROM HURRICANE
MARIE.  NORMALLY...WOULD EXPECT WIDESPREAD SHOWERS AND STORMS
UNDER THESE CONDITIONS BUT 12Z MODEL RUN HAS REALLY LOWERED
COVERAGE FROM 06Z RUN. ALSO...THE LATEST RADAR MOSAIC IS SHOWING
SOME CONVECTION ACROSS THE CWA BUT NOTHING REALLY TOO
IMPRESSIVE...YET.  THIS MORNINGS SHOWERS MOST LIKELY CREATED SOME
SUBSIDENCE THAT IS FINALLY NOW BEING OVERCOME BY DAYTIME HEATING
AND THE UPPER LEVEL SUPPORT. THE CONVECTION THAT HAS FORMED IS
MOVING AT A PRETTY GOOD CLIP SO HEAVY RAIN NOT TOO MUCH OF A
CONCERN AS OPPOSED TO SOME LARGE HAIL AND GUSTY OUTFLOW WINDS.
WITH ALL THIS IN MIND...DO EXPECT SOME CONVECTION BUT NOT UNTIL A
LITTLE LATER WITH SOME STRONG STORMS POSSIBLE.

THE BIG PICTURE CONTINUES TO SHOW AN AUTUMN-LIKE CLOSED LOW OVER
NRN NV WITH DECENT UPPER LEVEL SUPPORT DIGGING THE TROUGH
SOUTHWARD OVERNIGHT. AHEAD OF THE TROUGH...WEAK DISTURBANCES WILL
ALLOW SOME PRECIP TO CONTINUE THROUGH THE EARLY MORNING HOURS WITH
A DOWNTURN FROM ABOUT 6AM THROUGH NOON. AFTER THAT...A STRONG VORT
MAX WILL ARRIVE FROM THE SOUTHWEST WHILE PWATS REMAIN NEAR AN INCH
AIDING IN CONVECTIVE DEVELOPMENT WITH AREAS SOUTH LOOKING FAVORED
THOUGH ALL HIGHER TERRAIN WILL SEE A CHANCE FOR SOME SHOWERS AND
STORMS. THE PRECIP WILL CONTINUE INTO THE EVENING HOURS.

TEMPS WILL CONTINUE TO RUN SEVERAL DEGREES COOLER THAN NORMAL FOR
THIS TIME OF YEAR.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 315 PM MDT MON AUG 25 2014

WEDNESDAY THROUGH THURSDAY WILL BE UNSETTLED AS AN UPPER LOW
TRACKS SLOWLY ACROSS THE FORECAST AREA. WITH THE LOW CUTOFF FROM
THE POLAR JET THE SLOWER EC IS SOLUTION IS STILL FAVORED. THE LOW
MOVES INTO NE UTAH WEDNESDAY AFTERNOON...THEN OPENS AND SLOWLY
SLIDES SE OF THE FORECAST AREA BY THURSDAY. A DRY SLOT IS PROGGED
TO WORK INTO THE BASE OF THE LOW OVER SOUTHERN COLORADO ON
WEDNESDAY WITH DEEPER MOISTURE ORIGINATING FROM MARIE WRAPPING
AROUND INTO THE NORTHERN ZONES. THIS ENHANCEMENT RAKES THE
NORTHERN ZONES THROUGH WEDNESDAY NIGHT...THE CONTINENTAL DIVIDE ON
THURSDAY WITH A DRYING TREND FOR MUCH OF THE WESTERN CWA.
ASSOCIATED COLD CORE WEAKENS FORM -14C TO -11C AS IT PASSES OVER
THE CENTRAL- SOUTHERN CWA SO THE BEST MIX OF DEEP MOISTURE AND
INSTABILITY MAY BE OVER THE CENTRAL CWA. CLOUDS AND SHOWERS WILL
KEEP TEMPERATURES BELOW NORMAL. EASTERN SHOWERS ARE TIMED TO END
THURSDAY EVENING.

FRIDAY-SATURDAY HIGH PRESSURE CENTERED WEST OF SAN DIEGO ATTEMPTS
TO BUILD OVER THE REGION. BUT THE NEXT TROUGH FROM THE GULF OF
ALASKA DIGS INTO THE PACIFIC NW ON SATURDAY. THE GFS IS SLOWER TO
PROGRESS THIS TROUGH THROUGH THE NORTHERN ROCKIES WHILE THE EC
TIMES TROUGH PASSAGE ON MONDAY. EITHER SOLUTION STILL PRODUCES A
DRYING AND WARMING TREND.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1111 PM MDT MON AUG 25 2014

SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE ACROSS EASTERN
UTAH AND WESTERN COLORADO THROUGH 06Z TUESDAY. EXPECT LOCAL MVFR
CIGS AND VSBYS NEAR STRONGER STORMS WITH MOUNTAIN TOPS BECOMING
OBSCURED. LOCALLY HEAVY RAINFALL WILL OCCUR AS WELL...WITH
SOUTHWEST COLORADO BECOMING FAVORED AFTER 18Z.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...FLASH FLOOD WATCH FROM TUESDAY AFTERNOON THROUGH TUESDAY EVENING
     FOR COZ018-019-021>023.

UT...NONE.
&&

$$

UPDATE...PF
SHORT TERM...TGR
LONG TERM...JOE
AVIATION...JDC



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