Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 281008
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
408 AM MDT MON JUL 28 2014

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 408 AM MDT MON JUL 28 2014

THE HIGH PRESSURE CENTER SHIFTED TO THE TEXAS PANHANDLE OVER THE
PAST TWENTY-FOUR HOURS ALLOWING MOIST SUBTROPICAL AIR TO FLOW
NORTHWARD ACROSS THE FORECAST AREA. AS A RESULT...DEWPOINT TEMPS
WERE UP MARKEDLY ACROSS SOUTHERN COLORADO AND SOUTHEAST UTAH WITH
READINGS IN THE MID TO UPPER 50S EARLY THIS MORNING. INCREASED
ATMOSPHERIC MOISTURE COMBINED WITH A PAIR OF VORTICITY CENTERS HAS
SUSTAINED PERSISTENT SHOWERS OVER SW COLORADO AND EAST-CENTRAL
UTAH. NAM80 INDICATED 3H LEVEL DIVERGENCE ALSO PLAYING A ROLE.

SHORT RANGE MODELS INDICATED THAT SHOWERS LIKELY TO CONTINUE
BEYOND SUNRISE AND GIVEN DEEP MOISTURE THIS SEEMED REASONABLE. AS
DAYTIME WARMING DESTABILIZES THE ATMOSPHERE SHOWERS AND
THUNDERSTORMS WILL INCREASE IN COVERAGE AND INTENSITY. BUFR
SOUNDINGS INDICATE MESO-BETA ELEMENTS WILL BE SLOW MOVING AND
WITH PW VALUES RISING TO BETWEEN 1.1 AND 1.25 INCHES SOUTH OF THE
I-70 CORRIDOR SEEMS REASONABLE TO EXPECT EXCESSIVE RAINFALL FROM
THE STRONGEST CELLS. CONSEQUENTLY...WILL CONTINUE THE FLASH FLOOD
WATCH FROM NOON TO MIDNIGHT. IN FACT...EXPANDED THE WATCH TO
INCLUDE THE GRAND VALLEY AND THE GRAND FLAT IN EASTERN UTAH GIVEN
18 DEGREE RISE IN DEWPOINT AT KCNY. MODELS PROJECT THE DEEP
MOISTURE OVER SOUTHEAST UTAH WILL INFILTRATE THE GRAND VALLEY
DURING THE DAY.

TEMPERATURES SHOULD DROP BELOW NORMAL THIS AFTERNOON DUE TO
INCREASED CLOUDS AND SHOWERS. MET GUIDANCE SEEMED A BIT OVERLY
COOL SO STAYED CLOSER TO MAV GUIDANCE.

SHOWER AND THUNDERSTORM ACTIVITY WILL CONTINUE INTO THE EVENING
HOURS BEFORE SLOWLY DIMINISHING OVERNIGHT. MOIST MONSOONAL FLOW
WITH PRECIPITABLE WATER VALUES NEAR 1.30 INCHES WILL CONTINUE ON
TUESDAY AS AN UPPER LEVEL LOW CIRCULATION ROTATES EAST OVER THE
AREA. THIS COMBINATION WILL LEAD TO THE POSSIBILITY OF HEAVY RAIN
AND FLASH FLOODING ACROSS THE ENTIRE FORECAST AREA. THE BEST
DYNAMICAL FORCING WILL BE OVER THE NORTHERN HALF OF THE
AREA...RESULTING IN THE POTENTIAL FOR STRONGER STORMS ACROSS THE
NORTH. HOWEVER...EXTENSIVE CLOUD COVER MAY LIMIT AFTERNOON HEATING
OVER MOST AREAS. STAY TUNED TO SUBSEQUENT FORECASTS FOR THE
POSSIBILITY OF A FLASH FLOOD WATCH FOR TUESDAY.

.LONG TERM...(TUESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 408 AM MDT MON JUL 28 2014

SHOWER ACTIVITY WILL DIMINISH FROM SOUTH TO NORTH BY TUESDAY NIGHT
WITH RESIDUAL SHOWER ACTIVITY CONTINUING OVER THE NORTHERN
SECTIONS OVERNIGHT. MODELS ARE ADVERTISING ANOTHER WEAKER UPPER
LEVEL SYSTEM MOVING OVER THE NORTHERN SECTION OF THE FORECAST AREA
WITH GOOD MOISTURE REMAINING OVER THE ENTIRE AREA ON WEDNESDAY.
EXPECT ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS WITH BEST
COVERAGE OVER THE NORTH AND THE MOUNTAINS.

HIGH PRESSURE SHIFTS WEST CUTTING OFF THE MONSOONAL SURGE ON
THURSDAY. STILL PLENTY OF RESIDUAL MOISTURE IN PLACE WHICH WILL
FUEL AFTERNOON/EVENING SHOWERS AND THUNDERSTORMS EACH DAY THROUGH
THE END OF THE WEEK AND INTO THE WEEKEND. THIS ACTIVITY IS LIKELY
TO KEEP TEMPERATURES AT OR A LITTLE BELOW NORMAL THROUGH THE
PERIOD.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 408 AM MDT MON JUL 28 2014

ISOLATED TO SCATTERED SHOWERS ARE EXPECTED TO PERSIST WITHIN AN
AREA BOUNDED BY KEEO...KPSO...KPGA...KPUC...AND BACK TO KEEO.
ISOLATED THUNDERSTORMS ARE ALSO POSSIBLE. THIS ACTIVITY WILL HAVE
LITTLE IMPACT ON FLIGHT OPERATIONS AND EXPECT VFR CONDITIONS WILL
PERSIST THROUGH AT LEAST 17Z. DEEP MONSOONAL MOISTURE WILL FUEL
SCATTERED TO NUMEROUS THUNDERSTORMS...ESPECIALLY SOUTH OF THE I-70
CORRIDOR. THERE IS A GOOD CHANCE THAT SOME STORMS WILL MOVE OVER
AREA TAF SITES FROM AROUND 20Z THROUGH 03Z/TUES. A MAJORITY OF
TODAY/S STORMS WILL BE CAPABLE OF GENERATING HEAVY RAIN WHICH WILL
LIKELY RESULT IN IFR VSBY AND MVFR CIGS. IN ADDITION...SOME STORMS
WILL BE CAPABLE OF GENERATING OUTFLOW WINDS OF 30 MPH OR MORE.
THERE WILL BE A DECREASE IN ACTIVITY AFTER 03Z BUT SHOWERS AND
A FEW THUNDERSTORMS WILL CONTINUE THROUGH THE REMAINDER OF THE
NIGHT. IMPACTS UPON AREA TAF SITES LESS LIKELY DURING THIS PERIOD
HOWEVER.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...FLASH FLOOD WATCH FROM NOON MDT TODAY THROUGH THIS EVENING FOR
     COZ009-011-012-014-017>023.

UT...FLASH FLOOD WATCH FROM NOON MDT TODAY THROUGH THIS EVENING FOR
     UTZ022-028-029.

&&

$$

SHORT TERM...NL/MPM
LONG TERM...MPM/NL
AVIATION...NL



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