Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 041718
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1118 AM MDT TUE AUG 4 2015

.UPDATE...
ISSUED AT 1110 AM MDT TUE AUG 4 2015

AT 11 AM VALLEY INVERSIONS WERE BREAKING ACROSS THE REGION WITH
W-NW WINDS BEGINNING TO GUST AT SOME LOCATIONS. GUSTS TO 25 MPH
WILL BE COMMON THIS AFTERNOON...A BIT STRONGER NEAR THE
CONTINENTAL DIVIDE. CONVECTIVE TEMPERATURE WILL BE REACHED BY
EARLY AFTERNOON. WITH THE RIDGE BUILDING IN FROM THE WEST TODAY
INSTABILITY WILL BE LIMITED. WITH NO APPARENT FORCING TODAY...
STORMS ARE EXPECTED TO END WITH SUNSET. UNDER CLEARING SKIES AND
LIGHT GRADIENT...TEMPERATURES TONIGHT WILL BE BELOW GUIDANCE AND
BELOW NORMAL.

&&

.SHORT TERM...(TODAY THROUGH WEDNESDAY)
ISSUED AT 433 AM MDT TUE AUG 4 2015

HIGH PRESSURE BUILDS OVER THE REGION TODAY RESULTING IN A DRAMATIC
CHANGE FROM THE RECENT COOL AND STORMY WEATHER. HOWEVER...A FEW
ISOLATED THUNDERSTORMS REMAIN POSSIBLE OVER THE HIGH TERRAIN THIS
AFTERNOON...BUT OTHERWISE CONDITIONS WILL BE DRY. HIGHS WILL
REBOUND TO NEAR NORMAL TODAY...RISING SLIGHTLY ABOVE NORMAL ON
WEDNESDAY. ALSO ON WEDNESDAY...A 500 MB TROUGH FEATURE BRUSHING
NORTHERN UTAH AND SOUTHWEST WYOMING WILL CAUSE THE PRESSURE
GRADIENT TO TIGHTEN YIELDING INCREASED WINDS DURING THE AFTERNOON.

.LONG TERM...(WEDNESDAY NIGHT THROUGH MONDAY)
ISSUED AT 433 AM MDT TUE AUG 4 2015

MODELS INDICATED THAT THE BREAK IN THE MONSOONAL PATTERN WILL
CONTINUE INTO THURSDAY. A LOW PRESSURE SYSTEM MOVING EASTWARD
ACROSS THE NORTHERN ROCKIES WILL FLATTEN THE RIDGE OVER THE AREA
BRINGING A DRY WESTERLY FLOW. HOWEVER...THERE IS A SMALL CHANCE
THAT THERE MAY BE SUFFICIENT MOISTURE TO FUEL A HANDFUL OF STORMS
OVER THE MOUNTAINS ALONG THE DIVIDE DURING THE AFTERNOON AND EARLY
EVENING.

THE NEXT MONSOONAL SURGE ARRIVES FRIDAY AS A LOW PRESSURE SYSTEM
OVER THE EASTERN PACIFIC MOVES ASHORE OVER CENTRAL CALIFORNIA. IN
RESPONSE...HIGH PRESSURE SHIFTS EASTWARD TO THE TEXAS PANHANDLE
ALLOWING SOUTHWEST WINDS TO CARRY MOISTURE FROM THE MEXICAN PLATEAU
ACROSS THE AREA. PRECIPITABLE WATER (PW) VALUES ARE INDICATED TO
RISE MARKEDLY...ESPECIALLY OVER SOUTHEAST UTAH WHERE PW WILL RISE
TO NEAR AN INCH BY DAYS END. THIS WILL RESULT IN AN INCREASE IN
SHOWER AND THUNDERSTORM COVERAGE...ESPECIALLY ACROSS THE SOUTHERN
MOUNTAINS.

MOISTURE DEPTH ACROSS THE FORECAST AREA WILL INCREASE SATURDAY AS
SOUTHWEST FLOW CONTINUES TO BRING MONSOON MOISTURE TO THE REGION.
A SHORTWAVE TROUGH EJECTED FROM THE WEST COAST LOW PRESSURE SYSTEM
WILL SWEEP NORTHEASTWARD ACROSS THE GREAT BASIN PROVIDING SOME
ADDITIONAL LIFT. CONSEQUENTLY...EXPECT AN INCREASE IN BOTH
INTENSITY AND COVERAGE OF THUNDERSTORMS SATURDAY AFTERNOON INTO
SATURDAY EVENING.

AS THE SHORTWAVE CONTINUES ACROSS THE NORTHERN ROCKIES...FLOW
REVERTS TO A DRIER ZONAL ORIENTATION WHICH WILL CAUSE STORMS TO
DECREASE SUNDAY AND MONDAY.

HIGHS WILL BE NEAR NORMAL IN ZONAL FLOW THURSDAY...TRENDING
DOWNWARD FRIDAY AND SATURDAY AS THE MONSOON REASSERTS ITSELF.
DRYING WILL BRING WARMING SUNDAY INTO MONDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY NOON)
ISSUED AT 1110 AM MDT TUE AUG 4 2015

EXPECT A FEW THUNDERSTORMS OVER THE HIGHER TERRAIN THROUGH 02Z.
THIS ACTIVITY IS UNLIKELY TO IMPACT AIRPORTS ACROSS THE REGION AND
VFR CONDITIONS ARE EXPECTED TO PREVAIL DURING THE NEXT 24 HOURS.


&&

.FIRE WEATHER...
ISSUED AT 433 AM MDT TUE AUG 4 2015

FIRE WEATHER CONCERNS ARE POSSIBLE WEDNESDAY IN EASTERN UTAH AND
NORTHWEST COLORADO WHERE FUELS ARE CRITICAL DUE TO INCREASED
WINDS FROM A PASSING WEATHER DISTURBANCE TO THE NORTH. RIGHT NOW
FORECAST MODELS SHOW BORDERLINE MINIMUM RELATIVE HUMIDITY VALUES
WEDNESDAY AFTERNOON...BUT WIND GUSTS GREATER THAN 25 MPH ARE WELL
SUPPORTED. WILL KEEP AN EYE OUT FOR POTENTIAL PROBLEMS WEDNESDAY.

&&

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

$$

UPDATE...JOE
SHORT TERM...JAM
LONG TERM...NL
AVIATION...NL/JOE
FIRE WEATHER...JAM



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