Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 011755
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1155 AM MDT WED JUL 1 2015

.UPDATE...
ISSUED AT 1155 AM MDT WED JUL 1 2015

EMBEDDED SHORT WAVE IN LIGHT NW FLOW HAS PRODUCED A SMALL CLUSTER
OF SHOWERS WITH OCCASIONAL LIGHTNING OVER THE TAVAPUTS AND ROAN
PLATEAU. SHEAR PROFILE IS WEAK AND WILL BE DIFFICULT ENVIRONMENT TO
SUSTAIN DEEP ONGOING CELLS. HAVING SAID THAT...SOME STORMS WILL
ROLL OFF THE HIGH TERRAIN AND TRACK SOUTHEAST. GIVEN THE WEAK
SHEAR...CELLS WILL WEAKEN OR COLLAPSE AS THEY MOVE INTO VALLEY
AREAS. SO ANTICIPATE STORMS WILL BE THE GUSTY WIND VARIETY FOR
VALLEY LOCATIONS. ISOLATED HEAVY SHOWERS MAY OCCUR GIVEN THE
RELATIVELY MOIST SOUNDING (PWATS OF 0.90 ON THE MORNING
SOUNDING)...BUT THESE WILL BE MOSTLY RESERVED FOR THE HIGHER
ELEVATIONS (MOSTLY ABOVE 6K-7K FEET).

AS THE DISTURBANCE MOVES DOWNSTREAM...MANY STORMS WILL BE ENDING
LATE IN THE EVENING. THE EXCEPTION MAY BE THE SW COLORADO CORNER
WHERE ISOLATED STORMS MAY LINGER A BIT LONGER.

&&

.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 436 AM MDT WED JUL 1 2015

AS MENTIONED IN PREVIOUS DISCUSSIONS...THE PATTERN WILL UNDERGO A
SMALL SHIFT OVER THE NEXT 48 HOURS. THE HIGH CENTERED OVER WEST-
CENTRAL UTAH FOR THE PAST SEVERAL DAYS IS PROGGED TO SHIFT TO THE
WEST- NORTHWEST DURING THE DAY SETTLING OVER CENTRAL NEVADA BY
DAYS END. AS THIS OCCURS...A SHORTWAVE ROTATING THROUGH THE
NORTHERN QUADRANT OF THE HIGH WILL DRIFT ACROSS NORTHERN UTAH AND
OVER WESTERN COLORADO LATER IN THE DAY. A DECENT SLUG OF MOISTURE
MOVING AHEAD OF THE DISTURBANCE WILL BRING PRECIPITABLE WATER
VALUES (PW) NEAR 1 INCH. THE COMBINATION OF INCREASED MOISTURE
...MID-LEVEL FORCING...AND DAYTIME HEATING WILL BRING INCREASED
SHOWER AND THUNDERSTORM COVERAGE TO THE REGION. GIVEN PW VALUES...
EXPECT STORMS WILL PRODUCE HEAVY RAIN AND THE POSSIBILITY OF
LOCALIZED FLOODING. INCREASED CLOUDS AND SHOWERS WILL BRING A
SMALL MEASURE OF RELIEF FROM THE HEAT WITH AFTERNOON HIGHS A FEW
DEGREES COOLER (RELATIVE TERM) THAN OVER THE PAST TWO WEEKS.

STORMS WILL DIMINISH DURING THE EVENING...MORE RAPIDLY ACROSS THE
NORTH AS DRIER AIR FILTERS INTO THE AREA FROM THE NORTHWEST...
GRADUALLY SPREADING INTO THE SOUTH BY MORNING. SHOWERS AND
THUNDERSTORMS WILL REDEVELOP THURSDAY AFTERNOON THOUGH COVERAGE
WILL BE GREATLY REDUCED AS PW VALUES DIP TO NEAR 0.6 OF AND INCH
ON AVERAGE OVER THE AREA. THIS ACTIVITY WILL BE LARGELY CONFINED
TO THE CONTINENTAL DIVIDE. AFTERNOON HIGHS WILL REMAIN ABOVE
NORMAL BUT NOT QUITE AS HOT AS IN RECENT DAYS.

.LONG TERM...(THURSDAY NIGHT THROUGH TUESDAY)
ISSUED AT 436 AM MDT WED JUL 1 2015

THURSDAY NIGHT THROUGH SATURDAY...THE MIDRANGE MODELS SHOW DRIER
AIR SPREADING ACROSS THE AREA FROM NW TO SE...THOUGH MOISTURE WILL
LINGER OVER SW CO AND ALONG THE CONTINENTAL DIVIDE FOR SCATTERED
AFTERNOON AND EVENING CONVECTIVE DEVELOPMENT.

SUNDAY THROUGH TUESDAY...SUNDAY SHOULD SEE THE BEGINNING OF A CHANGE
TO WHAT LOOKS LIKE...I DARE SAY...A MONSOON PATTERN. BY SUNDAY
MORNING THE GFS SHOWS HIGH PRESSURE INTRUDING INTO THE WESTERN
GULF OF MEXICO AS THE GREAT BASIN HIGH CENTER MOVES TO THE FOUR
CORNERS. MOISTURE BEGINS TO FLOW NORTH OVER NORTHWESTERN MEXICO
AND INTO AZ AND SRN NEW MEXICO. A DISTINCT PLUME IS PROJECTED TO
STRETCH NORTH OVER AZ INTO UT BY MONDAY MORNING. SUNDAY NIGHT...IN
THE WESTERLIES OVER THE NORTHERN TIER STATES...A COLD FRONT WILL
PUSH INTO SOUTHERN WY AND PULL THE UT MOISTURE PLUME EAST OVER
EASTERN UT AND WESTERN CO MONDAY AFTERNOON. BY TUE THE MODELS SHOW
THIS MOISTURE BEING PULLED FURTHER EAST AND BENDING OVER
SOUTHEASTERN COLORADO. SO IT LOOKS WHAT MAY BE OUR FIRST MONSOONAL
PUSH WILL BE RELATIVELY BRIEF AND DRIER AIR STARTS FILTERING IN
FROM THE WEST TUE AFTERNOON.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1155 AM MDT WED JUL 1 2015

ALL TAF SITES WILL BE IN THE VICINITY OF -TSRA THIS AFTERNOON.
ERRATIC GUSTY WINDS (MOST GUSTS IN THE 25-35KT RANGE) WILL BE THE
MAIN THREAT ALTHOUGH ISOLATED +TSRA WILL BE POSSIBLE OVER THE
NRN/CENTRAL MOUNTAINS. THUNDERSTORM ACTIVITY WILL DIMINISH AROUND
SUNSET...BUT COULD LINGER BETWEEN 06Z-10Z OVER SOUTHWEST
COLORADO.

NO HAZARDOUS WEATHER IS EXPECTED BETWEEN 10Z-18Z LATE TONIGHT.

&&

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

$$

UPDATE...PF
SHORT TERM...NL
LONG TERM...CC
AVIATION...PF


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