Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 261640
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1040 AM MDT WED AUG 26 2015

.UPDATE...
ISSUED AT 1040 AM MDT WED AUG 26 2015

NO SURPRISES IN THE MORNING MODEL RUN. MOISTURE CONTINUES TO SURGE
THROUGH UTAH AND FAR SW COLORADO. TWO DISTURBANCES TO IMPACT THE
FORECAST AREA. THE FIRST LIFTS THROUGH EASTERN UTAH AND FAR
WESTERN COLORADO THROUGH THE MORNING AND EARLY AFTERNOON.
WIDESPREAD CLOUD COVER AND MARGINAL INSTABILITY WILL LIMIT
RAINFALL AMOUNTS WITH THIS WAVE. THE MORNING MODELS STILL
EMPHASIZE SE UTAH WITH HEAVIER RAINFALL AMOUNTS TODAY. SOME AREA
OF PARTIAL CLEARING WAS MOVING INTO SE UTAH THIS MORNING WHICH
SHOULD HELP DESTABILIZE THIS EARLY AFTERNOON. FLOW WILL VEER FROM
S TO SW. STORM MOTION OF SW25KTS WILL LIMIT RAINFALL AMOUNTS FROM
ANY ONE STORM.

SECOND OPEN DISTURBANCE OVER SW UTAH WORKS NE ACROSS THE FORECAST
AREA THIS EVENING. THIS FORCING WILL FAVOR NE UTAH AND SOUTHWARD
ALONG THE UT-CO BORDER. THIS IS THE BEST CHANCE FOR HEAVIER
SHOWERS WITH PRECIP WATER VALUES AT 1.5 INCHES IN EASTERN UTAH AND
FAR WESTERN COLORADO. WET BULB ZERO LEVEL AT 15KFT DOES NOT RULE
OUT SMALL HAIL WITH THE STRONGER STORMS. BEST FORCING WORKS INTO
THE PARK AND ELKHEAD MTNS AFTER MIDNIGHT. FLOW VEERS TO W AND
ADVECTS SOME DRIER AIR FOR THE WESTERN FORECAST AREA.

&&

.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 335 AM MDT WED AUG 26 2015

A VIGOROUS SHORTWAVE WILL MOVE NORTHEAST OUT OF ARIZONA TODAY.
MOISTURE IS QUITE ABUNDANT WITH THIS SYSTEM...WITH PRECIPITABLE
WATER VALUES OVER AN INCH BY THIS AFTERNOON OVER THE WESTERN TWO-
THIRDS OF THE FORECAST AREA.  THE BEST FOCUS FOR PRECIPITATION
DURING THE MORNING HOURS WILL BE OVER UTAH AND SLOWLY SPREAD NORTH
OVER THE REMAINDER OF THE FORECAST AREA DURING THE AFTERNOON AND
EVENING HOURS. IN SPITE OF FAIRLY GOOD UPPER-LEVEL SUPPORT WITH THIS
WAVE...EXPECT EXTENSIVE CLOUD COVER TO INHIBIT OPTIMAL HEATING AND
INSTABILITY DURING THE DAY. IN ADDITION...STORM MOVEMENT SHOULD BE
FAIRLY ADEQUATE. THEREFORE...HAVE DECIDED AGAINST ANY HIGHLIGHTS AT
THIS TIME...BUT WOULD NOT RULE OUT THE POSSIBILITY OF LOCALLY HEAVY
RAIN AND SMALL HAIL IN THE STRONGER STORMS. MODELS SHOW A FAIRLY
WIDESPREAD PRECIPITATION SWATH PUSHING EAST ACROSS THE FORECAST AREA
OVERNIGHT. THE BEST FOCUS WILL BE DURING THE EVENING HOURS WITH
PRECIPITATION SLOWLY DIMINISHING FROM WEST TO EAST THROUGH THURSDAY
MORNING. EXPECT DRYING CONDITIONS BY THURSDAY AFTERNOON WITH
RESIDUAL MOISTURE AND AFTERNOON HEATING ALLOW CHANCE
SHOWERS/THUNDERSTORMS OVER HIGHER TERRAIN. EXPECT MUCH COOLER
TEMPERATURES THROUGH THE SHORT TERM PERIOD WITH SEASONABLY COOL
TEMPERATURES EXPECTED.

.LONG TERM...(THURSDAY NIGHT THROUGH TUESDAY)
ISSUED AT 335 AM MDT WED AUG 26 2015

RIDGE AMPLIFIES OVER UTAH BEHIND DEPARTING SHORT WAVE...AND THIS
WILL HAVE STABILIZING INFLUENCE ON THE AIR MASS THURSDAY NIGHT
INTO FRIDAY. DIURNALLY DRIVEN CONVECTION WILL STILL FORM OVER THE
HIGH COUNTRY FOR A FEW SHOWERS/STORMS...BUT MUCH OF THE FORECAST
AREA WILL BE MOSTLY SUNNY AND DRY.

SATURDAY THROUGH TUESDAY...PACIFIC ENERGY WILL BE SEASONABLY
STRONG ACROSS THE PACIFIC NORTHWEST/NRN ROCKIES REGION. HIGH
PRESSURE TAKES ON A POSITIVE TILT ORIENTATION FROM THE DESERT
SOUTHWEST TO THE CENTRAL PLAINS. THIS KEEPS A WEAK MONSOONAL TAP
INTO SW COLORADO THROUGH THE LONG TERM PERIOD. SHOWERS/STORMS WILL
BE DAILY OCCURRENCE OVER THE SAN JUAN MOUNTAINS...EXTENDING
NORTHWARD TO THE ELKS AND ALONG THE COLORADO SPINE.

SATURDAY COULD BE THE WARMEST DAY OF THE LONG TERM PERIOD...THEN
SLIGHT COOLING OCCURS WHEN THE RIDGE GETS PUSHED EASTWARD.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY NOON)
ISSUED AT 1040 AM MDT WED AUG 26 2015

EXPECT DETERIORATING CONDITIONS QUICKLY THIS EARLY AFTERNOON AS
-TSRA/-SHRA EXPAND ACROSS ERN UTAH AND SWRN COLORADO. SCATTERED
-TSRA/-SHRA EXPANDS AND BECOMES NUMEROUS BY 21Z THIS AFTERNOON AND
CONTINUING THROUGH 06Z WEDNESDAY EVENING. CIGS BELOW ILS
BREAKPOINT WILL BE COMMON FOR SKI COUNTRY TAF SITES. IN
ADDITION...LOCAL VIS AOB 3SM +TSRAGS WILL BE POSSIBLE (MOSTLY
SOUTH OF I70). SHOWERS/STORMS WILL SLOWLY DISSIPATE AFTER 06Z THIS
EVENING EXCEPT FOR NW CO AIRPORTS INCLUDING KCAG KHDN KSBS. SCT
-TSRA WITH MTNS OCNLY OBSCURED CONTINUE EAST OF A LINE FROM KVEL
SSE TO KDRO.


&&

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

$$

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



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