Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 060458
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1058 PM MDT SUN JUL 5 2015

.UPDATE...
ISSUED AT 1050 PM MDT SUN JUL 5 2015

THE DISTURBANCE WAS PASSING EAST LATE SUNDAY EVENING. ISOLATED
SHOWERS ARE EXPECTED THROUGH TONIGHT ACROSS THE NORTHERN BORDER
AND ALSO IN SE UT AND FAR SW CO.

MONDAY...THE RIDGE IS FLATTENED INTO THE DESERT SW. A CLOSED LOW
OFF THE CALIFORNIA COAST PUSHES ONSHORE BY TUESDAY. THIS PATTERN
WILL BRING A DOWNTURN IN SHOWERS MONDAY BUT ANOTHER SURGE ON
TUESDAY. W-NW FLOW ALOFT WILL BRING IN SLIGHTLY DRIER AIR...WITH
PRECIP WATER VALUES BETWEEN 0.75 AND 1.0 INCH. THIS IS ONLY DRY IN
RELATION TO THE NEAR RECORD MOISTURE AMOUNTS WE HAD OVER THE
WEEKEND. ISOLATED MORNING SHOWERS AND STORMS WILL BECOME SCATTERED
MONDAY AFTERNOON FAVORING THE MOUNTAINS AND SOUTHERN VALLEYS
WHERE MOISTURE IS DEEPEST. TEMPERATURES WILL RECOVER CLOSER TO
NORMAL MONDAY AFTERNOON...STILL NICELY COOLER THAN THE HOT
CONDITIONS OF LAST WEEK.

MONDAY NIGHT...WEAK DISTURBANCES ARE RESOLVED DIFFERENTLY IN THE
MODELS BUT HINT AT WEAK FORCING THAT MAY KEEP A FEW STORMS GOING
THROUGH THE NIGHT. NO PORTION OF THE FORECAST AREA LOOKS FAVORED
FOR SHOWERS.

TUESDAY...AS THE LOW PUSHES TOWARDS THE CALIFORNIA COAST THE SW
RIDGE WEAKENS. FLOW TURNS TO WSW AND ALLOWS DEEPER MOISTURE TO
BEGIN TO RETURN. A MORE ORGANIZED DISTURBANCE LIFTS INTO SE UTAH
THROUGH THE AFTERNOON. STORM COVERAGE WILL INCREASE FROM SW TO NE
THROUGH THE DAY. DAYTIME TEMPERATURES TAKE ANOTHER DIP UNDER
CLOUDS AND SHOWERS.

&&

.SHORT TERM...(TONIGHT THROUGH MONDAY NIGHT)
ISSUED AT 306 PM MDT SUN JUL 5 2015

CLASSIC MONSOON PATTERN FEATURING HIGH PRESSURE OVER WEST TEXAS
AND LOW PRESSURE OFF THE CALIFORNIA COAST HAS BROUGHT DEEP
SUBTROPICAL MOISTURE TO THE FORECAST AREA. PRECIPITABLE WATER (PW)
AS MEASURED AT 12Z AT KGJT WAS 1.29 INCHES...OR NEARLY 2 TIMES
NORMAL. A SHORTWAVE TROUGH MOVING NORTHEASTWARD ACROSS NORTHEAST
UTAH AND NORTHWEST COLORADO SUSTAINED CLOUDS AND LIGHT SHOWERS
OVER THE AREA DURING THE EARLY PART OF THE DAY. MEANWHILE...
THUNDERSTORMS BEGAN TO DEVELOP OVER SOUTHEAST UTAH WHERE CLOUDS ON
THE WESTERN EDGE OF THE MOISTURE PLUME HAD DIMINISHED.

EXPECT DIURNALLY DRIVEN STORMS WILL CONTINUE THROUGH SUNSET WITH
SLOW MOVEMENT AND MOIST SUB-CLOUD LAYER POINTS TO AREAS OF HEAVY
RAIN AND LOCALIZED FLOODING...ESPECIALLY OVER THE SOUTH WHERE
INSOLATION WAS FAVORED GIVEN LATEST SATELLITE TRENDS. MEANWHILE
...MODELS INDICATED THAT THE SHORTWAVE WILL BE OVER THE DIVIDE BY
00Z/MON. LIMITED INSOLATION DUE TO CLOUDS COMBINED WITH SUBSIDENCE
ON THE BACK SIDE OF THE TROUGH AXIS SHOULD INHIBIT STRENGTH AND
COVERAGE OF THUNDERSTORMS ACROSS THE NORTH THIS EVENING. DIURNAL
COOLING IN THE ABSENCE OF FORCING WILL CAUSE SHOWERS AND
THUNDERSTORMS TO DIMINISH LATER THIS EVENING FOR MOST AREAS.
HOWEVER...MODELS SUGGEST ANOTHER SHORTWAVE MOVING THROUGH THE
NORTHERN ROCKIES WILL BRUSH THE NORTHERN BORDER OF THE FORECAST
AREA LATE TONIGHT POSSIBLY SUSTAINING A FEW NOCTURNAL SHOWERS
THROUGH SUNRISE MONDAY.

PASSAGE OF THE NORTHERN TROUGH WILL CAUSE FLOW TO SHIFT TO THE
WEST...TEMPORARILY ENDING THE INFLUX OF MOISTURE FROM THE MEXICAN
PLATEAU. AS A RESULT...MODELS SUGGEST PW VALUES WILL DIP TO NEAR
0.80 OF AN INCH ON AVERAGE. THIS LEVEL OF MOISTURE IS NOT
INCONSEQUENTIAL AND IS MORE THAN SUFFICIENT TO GENERATE SCATTERED
TO NUMEROUS SHOWERS AND THUNDERSTORMS OVER THE MOUNTAINS WITH A
FEW STORMS MOVING OVER THE ADJACENT VALLEYS. STEERING FLOW WILL
CONTINUE TO BE WEAK AND RESULTANT SLOW MOVING STORMS MAY BRING
LOCALIZED FLASH FLOODING. TO VARYING DEGREES...MODELS INDICATED A
WEAK SHORTWAVE MOVING OVERHEAD MONDAY NIGHT MAY SUSTAIN SHOWERS
AND EMBEDDED THUNDERSTORMS WELL INTO THE NIGHT.

CLOUDS AND SHOWER ACTIVITY ARE EXPECTED TO CONTINUE TO MODERATE
HIGH TEMPERATURES MONDAY WHILE HAVING AN OPPOSITE AFFECT ON
OVERNIGHT LOWS.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 306 PM MDT SUN JUL 5 2015

ZONAL FLOW WILL CONTINUE INTO TUESDAY WITH PW VALUES REMAINING
NEAR 0.75 OF AN INCH AS THE LOW REMAINS OFF THE CALIFORNIA COAST.
DIURNAL WARMING WILL FUEL ANOTHER ROUND OF SHOWERS AND
THUNDERSTORMS DURING THE AFTERNOON/EVENING TIME PERIOD. MODELS
HINT AT ANOTHER EASTWARD PROPAGATING SHORTWAVE TROUGH MOVING OVER
THE AREA TUESDAY NIGHT WHICH COULD SUSTAIN SHOWERS AND EMBEDDED
THUNDERSTORMS LATE INTO THE NIGHT.

FLOW VEERS BACK TO THE SOUTHWEST ON WEDNESDAY AS THE EASTERN
PACIFIC LOW PUSHES ASHORE OVER THE CENTRAL CALIFORNIA COAST LATE
IN THE DAY. MODELS HOLD THE LOW QUASI-STATIONARY THROUGH THURSDAY.
MOISTURE CHANGES LITTLE DURING THIS PERIOD SO EXPECT ANOTHER
ROUND OF DIURNALLY DRIVEN SHOWERS AND THUNDERSTORMS BOTH WEDNESDAY
AND THURSDAY.

STORMS LIKELY TO BE MORE ENERGETIC...ESPECIALLY ACROSS THE SOUTH...
ON FRIDAY AS A 50-60 KT JET ROUNDS THE BASE OF THE PACIFIC LOW AND
NOSES OVER THE FOUR CORNERS REGION. STEERING FLOW PICKS UP WHICH
WILL MOVE STORMS ALONG A BETTER CLIP WHICH...WHEN COMBINED WITH PW
VALUES FALLING BELOW 0.6 OF AN INCH...REDUCES THE THREAT OF FLASH
FLOODING. MODELS IN AGREEMENT WITH DRYING CONTINUING INTO THE
WEEKEND AS THE MOISTURE PLUME IS SHIFTED EASTWARD AHEAD OF THE
LOW. REGARDLESS...EXPECT A FEW STORMS TO FIRE EACH AFTERNOON AS PW
VALUES HOVER NEAR 0.40 TO 0.50 OF AN INCH.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY MIDNIGHT)
ISSUED AT 1050 PM MDT SUN JUL 5 2015

SCATTERED SHOWERS AND ISOLATED STORMS CONTINUE TONIGHT NEAR THE
WYOMING BORDER AND ALSO IN SE UT AND FAR SW CO. THROUGH 12Z...KCNY
KTEX KDRO MAY SEE -SHRA/-TSRA WITH CIGS BLO 070 AND ERRATIC GUSTS
TO 30 MPH. ANOTHER ROUND OF THUNDERSTORMS DEVELOPS AFTER 18Z
MONDAY...WITH LOCALLY HEAVY RAIN AND GUSTY WINDS TO POTENTIALLY
IMPACT TAF SITES ESPECIALLY KTEX AND KDRO. MOUNTAINS WILL BE
OBSCURED AT TIMES.


&&

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

$$

UPDATE...JOE
SHORT TERM...NL
LONG TERM...NL
AVIATION...JOE



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