Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 260534
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1134 PM MDT SAT JUL 25 2015

.UPDATE...
ISSUED AT 1130 PM MDT SAT JUL 25 2015

THE MONSOONAL MOISTURE STREAM REMAINED MOSTLY SOUTH AND EAST OF
THE FORECAST AREA ON SATURDAY. BUT AN INVERTED TROUGH IN SONORA
SUNDAY WILL HELP TO PULL THE MOISTURE STREAM BACK INTO THE FOUR
CORNERS THIS MORNING AND INTO THE CENTRAL ZONES THROUGH SUNDAY
AFTERNOON. PRECIP WATER VALUES CLIMB TO NEAR 1.1 INCH SOUTH OF
I-70. STORM MOTION WILL BE TO THE NE AT AROUND 20 MPH SO ONLY
LOCALIZED HEAVY SHOWERS ARE EXPECTED FAVORING THE SW SAN JUANS.
DRIER AIR REMAINS IN PLACE OVER THE NORTH RAISING FIRE WEATHER
CONDITIONS. ISOLATED HIGH-BASED STORMS MAY FORM NORTH OF I-70.
THESE STORMS IN AN INVERTED V ENVIRONMENT ARE EXPECTED TO PRODUCE
MORE GUSTY WIND AND LIGHTNING THAN RAIN.

SUNDAY NIGHT THE NE PACIFIC TROUGH WORKS INTO THE NORTHERN GREAT
BASIN. SW GRADIENT WINDS ALOFT CONTINUE TO INCREASE. THIS WILL
ERODE MOISTURE FROM WEST TO EAST THROUGH THE NIGHT BUT A FEW
STORMS CONTINUING PAST MIDNIGHT. MIN TEMPERATURES EXPECTED TO STAY
ON THE MILD SIDE OF NORMAL.

MONDAY THE TROUGH/S ASSOCIATED 90KT JET NOSES ACROSS NW UTAH THEN
LIFTS INTO WYOMING. AN ASSOCIATED DRY COOL FRONT PUSHES ACROSS NE
UT AND NW CO THROUGH THE AFTERNOON. SW 700-600MB GRADIENT WINDS
INCREASE TO 40KTS AHEAD OF THE FRONT. THIS SW FLOW IS ALSO QUITE
DRY SO ANY SHOWER OR STORM ACTIVITY WILL BE IN THE EASTERN MOST
MOUNTAINS.

&&

UPDATE ISSUED AT 813 PM MDT SAT JUL 25 2015

WINDS HAVE LESSENED ACROSS NORTHWEST COLORADO BELOW THE 25 MPH
THRESHOLD WITH FIRE WEATHER CONDITIONS NO LONGER EXPECTED SO HAVE
ALLOWED THE RED FLAG WARNING TO EXPIRE. ISOLATED SHOWERS WITH SOME
LIGHTNING STRIKES DEVELOPED LATER TODAY AROUND 4 PM OVER THE
EASTERN SAN JUANS WITH MOSTLY SUNNY SKIES ELSEWHERE. REST OF
FORECAST REMAINS ON TRACK WITH THE SHOWERS OVER THE SAN JUANS
EXPECTED TO DISSIPATE AFTER SUNSET. MOISTURE AND CLOUDS INCREASE
FROM THE SOUTH EARLY SUNDAY MORNING WITH SHOWERS AND STORMS
INCREASING SUNDAY AFTERNOON AND EVENING.

&&

.SHORT TERM...(TONIGHT THROUGH SUNDAY NIGHT)
ISSUED AT 312 PM MDT SAT JUL 25 2015

ATYPICAL JULY AFTERNOON IN A COUPLE OF WAYS...NO CONVECTIVE STORMS
AS OF 19Z. HRRR AND RAP INDICATE THAT A STORM OR TWO WILL POP OVER
THE SAN JUANS LATER THIS AFTERNOON AND PROMPTLY MOVE EAST.
CONVECTIVE ACTIVITY HAS DOMINATED THIS JULY...SO THE LACK OF
STORMS SEEMS OUT OF PLACE. ABUNDANT SUNSHINE PREVAILS TODAY BUT
HARDLY A SCORCHER. OUTSIDE OF MONUMENT VALLEY...NO TEMP SENSOR
HAVE REACHED 90F BY 1 PM. THE DRY SOUTHWEST FLOW WITH HIGH
PRESSURE CENTERED OVER THE SRN PLAINS HAS PROVIDED OUR FORECAST
AREA WITH A COMFORTABLE AND QUIET SUMMER DAY.

MOISTURE INCREASES FROM THE SOUTH EARLY SUNDAY MORNING RESULTING
IN CLOUD COVER INCREASING ACROSS SOUTHWEST COLORADO. SHOWERS ARE
EXPECTED TO BEGIN DEVELOPING BY NOON AND INCREASE IN COVERAGE AND
INTENSITY THROUGHOUT THE DAY SUNDAY AS 500 MB VORTICITY STREAMS
SOUTHWEST TO NORTHEAST ACROSS AN AREA FAIRLY SIMILAR TO YESTERDAY
BUT THE MOISTURE SHIELD REACHING FURTHER NORTH. THIS PLUME OF
MOISTURE LOOKS TO MOVE OFF TO THE EAST AND DISSIPATE ON SUNDAY
EVENING AS DRIER AIR PROTRUDES INTO WESTERN COLORADO FROM THE
GREAT BASIN. NORTHWEST COLORADO AND NORTHEAST UTAH WILL REMAIN DRY
AND BREEZY WITH THE ACTIVITY TO THE SOUTH AND A 60 KT JET
OVERHEAD.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 312 PM MDT SAT JUL 25 2015

A BURLY PACIFIC NORTHWEST TROUGH WILL PUSH EAST ACROSS THE
INTERMOUNTAIN WEST BEGINNING ON MONDAY AND BRUSH ALONG THE
WY/UT/CO BORDER MONDAY EVENING INTO TUESDAY. WINDS AHEAD OF THE
TROUGH ON MONDAY WILL BE ENHANCED WITH VERY GUSTY WINDS ALONG THE
NORTHERN UT/CO BOUNDARIES THANKS TO THE INCREASE PRESSURE GRADIENT
AND A 60 KT JET ALOFT. ASSUMING RELATIVE HUMIDITY VALUES CAN DRY
OUT ENOUGH IN THE AFTERNOON AS FORECAST MODELS HAVE BEEN SHOWING
FOR DAYS...WINDY AND DRY CONDITIONS DO LOOK PROBABLE IN NE UTAH
AND NW COLORADO. MOISTURE ON MONDAY WILL HUG THE SAN JUANS AND
SOUTHERN COLORADO DIVIDE MOUNTAINS SO SHOWERS AND A FEW ISOLATED
TSTORMS ARE POSSIBLE IN THESE AREAS.

THE NAM IS BRINGING A SOLID ELONGATED VORT MAX TO THE WY/UT/CO
BORDER ON TUESDAY LINED UP WITH THE ULJ WHILE THE GFS AND EC ARE
KEEPING THIS ENERGY A BIT FURTHER NORTH. THIS ENERGY STAYS IN
WYOMING BUT MAY KEEP CONDITIONS BREEZY ALONG THE WY/UT/CO BORDER.
500 MB HIGH PRESSURE BEGINS TO BACK TO THE WEST OVER THE FOUR
CORNERS LATER IN THE DAY ON TUESDAY. THIS HIGH PRESSURE WILL BE
CENTERED OVER THE SOUTHWEST AND GREAT BASIN BY THURSDAY AND
THROUGH SATURDAY. 700 MB ISOBARS SHOW CENTER OF HIGH PRESSURE AT
THAT LEVEL OVER WESTERN KS...WESTERN OK...AND THE PANHANDLE OF TX
WHICH WOULD STREAM MOISTURE INTO THE FOUR CORNERS FROM THE GULF.
SIGNAL LOOKS SLIGHTLY MONSOONAL AT THE END OF NEXT WEEK AS THIS
HIGH PRESSURE PATTERN SETS UP.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1051 PM MDT SAT JUL 25 2015

VFR CONDITIONS WILL PREVAIL AT THE AREA FORECAST TERMINALS THE
NEXT 24 HOURS. THE MORE NOTICEABLE CHANGE WILL BE INCREASING MID
AND HIGH LEVEL CLOUDINESS AND IN INCREASED COVERAGE OF SHOWER AND
THUNDERSTORM ACTIVITY SUNDAY AFTERNOON. THE MAIN THREAT FROM THESE
SHOWERS/STORMS WILL BE ERRATIC AND GUSTY OUTFLOW WINDS IMPACTING
FLIGHT OPERATIONS. LOWERED FLIGHT CRITERIA PROBABILITY IS QUITE
LOW ATTM BUT PASSING STORMS MY IMPACT ILS BREAK POINTS AT
KEGE...KASE AND KRIL TEMPORARILY AFTER 26/20Z.


&&

.FIRE WEATHER...
ISSUED AT 1130 PM MDT SAT JUL 25 2015

THE FIRE WEATHER WATCH FOR COLORADO ZONE 200 FOR SUNDAY HAS BEEN
UPGRADED TO A RED FLAG WARNING DUE TO LOW AFTERNOON HUMIDITY...
GUSTY WINDS...AND HAINES INDEX OF 6. ISOLATED AFTERNOON
THUNDERSTORMS ARE POSSIBLE THAT WOULD PRODUCE GUSTY OUTFLOW WINDS
AND LIGHTNING BUT LITTLE RAIN. WINDS ARE EXPECTED TO DIMINISH
AFTER 8 PM.

ALSO THE WATCH FOR MONDAY FOR FIRE ZONES 200 201 202 AND 203
REMAINS IN EFFECT WITH INCREASING CONFIDENCE FOR STRONG SOUTHWEST
WINDS AND LOW RH FOR MONDAY AS A DRY COLD FRONT PUSHES ACROSS
NORTHWEST COLORADO. WILL LET THE SUNDAY DAY SHIFT LOOK AT THIS
PERIOD IN DETAIL AND MAKE THE WARNING DECISION.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...FIRE WEATHER WATCH FROM MONDAY MORNING THROUGH MONDAY EVENING
     FOR COZ200>203.

     RED FLAG WARNING FROM 1 PM TO 8 PM MDT SUNDAY FOR COZ200.

UT...NONE.
&&

$$

UPDATE...JOE
SHORT TERM...PF/JAM
LONG TERM...JAM
AVIATION...15
FIRE WEATHER...JOE



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