Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 210300 CCA
AFDGJT

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
900 PM MDT SUN JUL 20 2014

.UPDATE...
ISSUED AT 900 PM MDT SUN JUL 20 2014

AREAL COVERAGE OF SHOWERS AND THUNDERSTORMS SHRINKING QUICKLY
THIS EVENING. MID LEVEL MOISTURE AND SHEAR WAS OKAY FOR LONGER
LIVED PULSE STORMS...BUT SUB CLOUD ENVIRONMENT REMAINED RELATIVELY
DRY AND CELLS STRUGGLED TO SUSTAIN ANY LASTING IMPACT. WITH THE
LOSS OF SURFACE HEATING...STORMS ARE BASICALLY DONE FOR THE NIGHT
EXCEPT FOR ISOLATED ACTIVITY OVER MOFFAT COUNTY.

&&

.SHORT TERM...(TONIGHT THROUGH MONDAY NIGHT)
ISSUED AT 252 PM MDT SUN JUL 20 2014

SHOWERS GOT AN EARLY START ACROSS PORTIONS OF EASTERN UTAH AND
NORTHWEST COLORADO WHERE SHORTWAVE ENERGY AND STRETCHING
DEFORMATION COINCIDED. BY MIDDAY...THUNDERSTORMS HAD BEGUN TO FIRE
OVER THE WESTERN COLORADO MOUNTAINS IN RESPONSE TO DAYTIME
HEATING AND INCREASED MOISTURE. AN INFLUX OF SUBTROPICAL MOISTURE
ONGOING IN SOUTHWESTERLY FLOW AND SPC MESO ANALYSES INDICATED
PRECIPITABLE WATER APPROACHING AN INCH OVER SOUTHEAST UTAH AND
NOW APPROACHING 0.75 ACROSS MUCH OF THE REMAINDER OF THE AREA.
THOUGH MOISTURE HAS INCREASED...MARGINAL CAPE APPEARS TO HAVE
LIMITED STORM STRENGTH AND CELLS WERE MOVING FAST ENOUGH TO LIMIT
RAINFALL AMOUNTS. THAT SAID...CANNOT ENTIRELY RULE OUT LOCALIZED
EXCESSIVE RAINFALL LATER THIS AFTERNOON AND INTO THIS EVENING.

A DEEPENING TROUGH OVER THE PACIFIC NORTHWEST WILL CAUSE HIGH
PRESSURE TO EASE EASTWARD OVER THE NEXT 24 HOURS AND DRIER AIR
BEGINS TO INFILTRATE. DIURNAL COOLING COMBINED WITH MID-LEVEL
DRYING SHOULD BRING AN END TO MOIST CONVECTION OVERNIGHT THROUGH
MONDAY MORNING. BY MONDAY AFTERNOON PW VALUES EXPECTED TO FALL
BELOW 0.40 INCHES ACROSS ALL BUT PORTIONS OF SOUTHWEST COLORADO.
THEREFORE...ONLY MENTIONED THUNDERSTORM POTENTIAL OVER THE SAN
JUANS. MEANWHILE...STRONG WINDS ALOFT OVER THE NORTH WILL GENERATE
BREEZY CONDITIONS OVER NORTHWEST COLORADO AND PORTIONS OF
NORTHEAST UTAH MONDAY AFTERNOON AND EARLY MONDAY EVENING. EXPECT
STORMS WILL DIMINISH EARLY MONDAY EVENING AS DRYING TREND
CONTINUES.

TEMPERATURES WILL BE A BIT ABOVE NORMAL MONDAY AFTERNOON WITH
OVERNIGHT LOWS NEAR SEASONAL NORMS.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 252 PM MDT SUN JUL 20 2014

HIGH PRESSURE CENTERED OVER SOUTHEAST COLORADO ON TUESDAY WILL
SLOWLY DRIFT WEST TO A POSITION NEAR THE FOUR-CORNERS REGION BY
LATE THURSDAY. SOME MOISTURE WILL PUSH NORTH INTO THE FORECAST
AREA BY LATE TUESDAY BRINGING A SLIGHT CHANCE OF LATE DAY SHOWERS
AND THUNDERSTORMS...MAINLY OVER THE HIGHER TERRAIN. SEVERAL WEAK
WAVES WILL PUSH NORTHEAST IN THE FLOW ON BOTH WEDNESDAY AND
THURSDAY BRINGING AN UPTICK IN MOISTURE AND RESULTANT SHOWERS AND
THUNDERSTORMS.

THE RIDGE OF HIGH PRESSURE WILL CONTINUE TO DRIFT WEST INTO
THE SOUTHWESTERN STATES AND FLATTEN THROUGH THE WEEKEND. AS THE
FLOW BECOMES WESTERLY/NORTHWESTERLY...DRIER WEATHER WILL MOVE
ACROSS THE AREA WITH ONLY A SLIGHT CHANCE OF LATE-DAY STORMS OVER
THE MOUNTAINS DURING THE WEEKEND. EXPECT TEMPERATURES TO REMAIN
SEASONABLY WARM THROUGH THE PERIOD.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)
ISSUED AT 900 PM MDT SUN JUL 20 2014

ISOLATED -SHRA/-TSRA WILL BE FINISHED BETWEEN 03Z-06Z THIS
EVENING. QUIET CONDITIONS OVERNIGHT AND MONDAY MORNING...BUT A FEW
-SHRA/-TSRA WILL FORM AFTER 18Z MONDAY. ISOLATED CONVECTIVE STORMS
WILL BE EAST OF A LINE FROM KCAG-KRIL-LTEX-KDRO. MOSTLY CLEAR
CONDITIONS ARE EXPECTED WEST OF THIS LINE.

LOCAL SURFACE GUSTS TO 25 KTS WILL BE POSSIBLE OVER NW COLORADO
MONDAY AFTERNOON.

&&

.FIRE WEATHER...
ISSUED AT 252 PM MDT SUN JUL 20 2014

PRESSURE GRADIENT ALOFT EXPECTED TO INCREASE MONDAY ACROSS THE
NORTHERN PORTION OF THE FORECAST AREA. CONCURRENTLY...DRIER AIR
WILL MOVE OVERHEAD AS THE MONSOONAL MOISTURE TAP IS PUSHED TO THE
EAST. DEEP MIXING WILL DRIVE SURFACE WINDS TO 15 TO 20 KTS
SUSTAINED WITH OCCASIONAL GUSTS TO 30 KTS. DAYTIME WARMING
COMBINED WITH AN INFLUX OF DRYING WILL CAUSE RELATIVE HUMIDITIES
TO FALL TO BETWEEN 10 TO 15 PERCENT MONDAY AFTERNOON AND EARLY IN
THE EVENING. THE COMBINATION OF LOW RH...STRONG SOUTHWEST WINDS
...AND DRY FUELS WILL LEAD TO CRITICAL FIRE WEATHER CONDITIONS
FOR PORTIONS OF NORTHWEST COLORADO AND NORTHEAST UTAH. CONFIDENCE
SUFFICIENT TO UPGRADE WATCH TO A RED FLAG WARNING FOR CO FIRE ZONE
200 FROM NOON TO 8 PM MONDAY. IN ADDITION...WILL EXPAND WARNING
AREA TO INCLUDE CO FIRE ZONE 202 AND UT FIRE WEATHER ZONES
483...484...AND 487.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...RED FLAG WARNING FROM NOON TO 8 PM MDT MONDAY FOR COZ200-202.

UT...RED FLAG WARNING FROM NOON TO 8 PM MDT MONDAY FOR UTZ483-484-487.

&&

$$

UPDATE...PF
SHORT TERM...NL
LONG TERM...MPM
AVIATION...PF
FIRE WEATHER...NL



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