Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 251733
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1133 AM MDT MON AUG 25 2014

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 400 AM MDT MON AUG 25 2014

ACTIVE PERIOD SETTING UP ONCE AGAIN AS ENERGY DIVING SOUTH ALONG
THE WEST COAST EVENTUALLY CLOSES OFF ANOTHER LOW OVER THE GREAT
BASIN. MOISTURE WILL BE RETURNING RATHER QUICKLY THROUGH THIS
PERIOD WITH SUBTROPICAL STREAM EVIDENT ON WATER VAPOR. BEST
MOISTURE TRANSPORT BRINGS THIS DEEPER STREAM ACROSS EASTERN UTAH
AND WESTERN COLORADO TODAY WITH FLOW EXPECTED TO BECOME A BIT MORE
SOUTHERLY AS THE LOW DROPS INTO THE GREAT BASIN. MORNING
CONVECTION TODAY WILL DIMINISH BY 9 AM...WITH BRIEF SUBSIDENT
PERIOD THROUGH EARLY THIS AFTERNOON BEFORE NEXT ROUND FIRES.
SEVERAL FACTORS COMING INTO PLAY TO KEEP THE DAY ACTIVE AS EXITING 60
KT JET GETS REPLACED BY APPROACHING 50 KTS JET STREAK. PRECIPITABLE
WATER VALUES INCREASE TO AROUND AN INCH OVER THE FOUR CORNERS WITH
THE DEEPER MOISTURE SPREADING NORTH AND EAST LATE TODAY. FORECAST
CAPE VALUES INDICATE BEST INSTABILITY UP NORTH TODAY...ALTHOUGH
OLD FRONTAL BOUNDARY AND QUICKER HEATING SHOULD FIRES STORMS ALONG
AND SOUTH OF THE FRONT...STALLED NEAR THE INTERSTATE 70
CORRIDOR...BY EARLY THIS AFTERNOON. POP FIELDS BUILT TO INDICATE
DIMINISHING MORNING ACTIVITY...FOLLOWED BY INCREASING SHOWERS AND
STORMS THROUGHOUT THE FORECAST AREA THIS AFTERNOON...WITH NORTHERN
ZONES FAVORED. POTENTIAL FOR A FEW STRONG TO POSSIBLY SEVERE
STORMS THIS AFTERNOON WITH DECENT WIND SHEAR AND DEEPER
INSTABILITY. MODEL GENERATED CAPE VALUES EXCEED 1500 J/KG ACROSS
PORTIONS OF NORTHEAST UTAH AND NORTHWEST COLORADO WITH LI VALUES
AROUND MINUS 6C. LARGE HAIL AND STRONG OUTFLOW WINDS COULD DEVELOP
AND WILL NEED TO BE MONITORED CLOSELY THIS AFTERNOON. TEMPERATURES
WILL BE RUNNING A FEW DEGREES WARMER ACROSS THE CENTRAL AND
SOUTHERN ZONES WITH PERSISTENCE READINGS EXPECTED FOR THE NORTH.

THE UPPER TROUGH CONTINUES TO DIG INTO NEVADA TONIGHT AND TUESDAY
EVENTUALLY FORMING A CLOSED MID-LEVEL LOW. MOISTURE IS DRAWN UP
FROM THE SOUTH AND SOUTHWEST AND INTO OUR FORECAST AREA AS IT DOES
SO...SO SKEWED THE HIGHER POPS TOWARD SE UT/SW CO INITIALLY. GFS
KEPT ITS FASTER TENDENCY BY MOVING THE UPPER LOW INTO WRN UT BY
LATE TUE WHILE THE 00Z NAM AND THE 12Z/24 EC HELD IT OVER NV.
LARGER SCALE LIFT AND FAVORABLE DIFLUENT FLOW AHEAD OF THE LOW
COUPLED WITH PRECIPITABLE WATER VALUES OF .80 TO 1.00 INCH SHOULD
PRODUCE SCATTERED TO NUMEROUS SHOWERS/THUNDERSTORMS TUESDAY
AFTERNOON.

.LONG TERM...(TUESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 400 AM MDT MON AUG 25 2014

THE CLOSED LOW SLOWLY MOVES ACROSS UT INTO CO TUESDAY NIGHT AND
WEDNESDAY FOR A CONTINUED CHANCE OF WET WEATHER. RATHER WEAK UPPER
JET MAX SLIDES ACROSS THE FOUR CORNERS. MOISTURE WRAPS BACK AROUND
THE COLD CORE LOW CENTER SITTING OVER NW CO (PER GFS) OR NE UT (PER
24/12Z ECMWF) BY WED AFTERNOON. ADJUSTED POPS TO FAVOR THE NORTH
HALF TO TWO-THIRDS OF THE FORECAST AREA. GFS AND ECMWF POINT TOWARD
SOME DRIER AIR WORKING INTO THE 4 CORNERS WITH THE JET PER 315K AND
320K THETA SURFACE RH. TEMPS COOLER.

UNSETTLED CONDITIONS NOW LOOK AS THOUGH THEY WILL PERSIST THROUGH
LATE THURSDAY AS THE UPPER LOW SLOWLY WORKS ACROSS COLORADO.
MOISTURE CONTINUES TO WRAP AROUND THE LOW WITH OROGRAPHIC
COMPONENT COMING INTO PLAY ACROSS THE WESTERN COLORADO MOUNTAINS.
EXPECT AT LEAST SCATTERED SHOWERS AND ISOLATED CONVECTION
THROUGH THIS PERIOD WITH TEMPERATURES RUNNING WELL BELOW NORMAL
FOR THIS TIME OF SEASON.

ONCE THE LOW MAKES THE JUMP OVER THE ROCKIES THURSDAY NIGHT...
CONDITIONS WILL DRY OUT WITH TEMPS WARMING AS WE MOVE INTO THE
WEEKEND.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1128 AM MDT MON AUG 25 2014

VISIBLE SATELLITE SHOWING SOME HIGH CLOUDS STREAMING OVER THE
SOUTHERN HALF OF THE CWA THIS MORNING WITH SOME CUMULUS BUILDING
OVER THE REMAINING HIGHER TERRAIN. AM EXPECTING CONVECTION TO GET
GOING HERE VERY SHORTLY WITH SHOWERS AND STORMS BECOMING COMMON.
MEDIUM CONFIDENCE THIS CONVECTION WILL AFFECT TAF SITES THIS AFTN
AND EVENING SO INCLUDED VCTS AND VCSH FOR MANY AERODROMES. UPPER
LEVEL WINDS WILL KEEP STORMS MOVING AT A GOOD PACE SO CONCERNS
TODAY WILL BE SOME HAIL AND GUSTY OUTFLOW WINDS. SOME SHOWERS AND
STORMS WILL PERSIST OVERNIGHT INTO TOMORROW WHEN MORE WIDESPREAD
PRECIP IS EXPECTED.

&&

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

$$

SHORT TERM...JDC/JAD
LONG TERM...JAD/JDC
AVIATION...TGR



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