Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 200303
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
903 PM MDT TUE MAY 19 2015

.UPDATE...
ISSUED AT 848 PM MDT TUE MAY 19 2015

SHOWERS AND ISOLATED THUNDERSTORMS CONTINUE TO SLOWLY MARCH
ENE THIS EVENING...WITH PUNCH OF DRIER AIR WORKING INTO THE
SOUTHERN ZONES. WILL CONTINUE TO UPDATE POPS GRIDS TO BRING THEM
MORE INTO LINE WITH CURRENT TRENDS. HRRR BRINGS ONE LAST WAVE OF
ENERGY OUT OF CENTRAL UTAH AND ACROSS OUR NORTHERN ZONES AFTER
MIDNIGHT...WHICH SHOULD CARRY A FEW LINGERING SHOWERS WITH IT.
AREAS SOUTH OF INTERSTATE 70 WILL BE DRYING OUT. EXPECT A CHILLY
NIGHT IN MOST AREAS WITH COMBINATION OF FALLING DEW POINT
TEMPS...CLEARING SKIES AND LIGHT WINDS.

&&

.SHORT TERM...(TONIGHT THROUGH WEDNESDAY NIGHT)
ISSUED AT 252 PM MDT TUE MAY 19 2015

THE LATEST PACIFIC STORM WAS CENTERED OVER THE SALT LAKE CITY AREA
EARLY THIS AFTERNOON. A WEAK SHORTWAVE ROTATING THROUGH THE BASE
OF THE ZONALLY ELONGATED LOW GOT THUNDERSTORMS OFF TO AN EARLY
START TODAY. SEVERAL STORMS GENERATED DIME-SIZED HAIL...THOUGH
WIND GUSTS WERE SUBSTANTIALLY WEAKER AS THE LOWER LEVELS OF THE
ATMOSPHERE HAVE MOISTENED THEREBY LIMITING DOWNDRAFT SPEED.
MEANWHILE...WEB CAM IMAGES FROM THE MOUNTAIN AREAS INDICATED SOME
SNOW HERE AND THERE BUT MOUNTAIN PASSES HAD ALL IMPROVED
SIGNIFICANTLY AS COMPARED TO THIS MORNING.

EXPECT SHOWERS AND THUNDERSTORMS WILL CONTINUE INTO THE EVENING
THOUGH THE LOSS OF DAYTIME HEATING COMBINED WITH THE EXIT OF THE
SHORTWAVE DESCRIBED PREVIOUSLY WILL CAUSE MOIST CONVECTION TO
DIMINISH SIGNIFICANTLY BY MIDNIGHT. MODELS INDICATED A FEW SHOWERS
MAY LINGER OVER THE HIGHER TERRAIN OF THE NORTH LATE TONIGHT IN AN
AREA OF WEAK OVERRUNNING...THOUGH ADDITIONAL SNOW ACCUMULATIONS
WILL BE LIGHT AND LOCALIZED. PARTIAL CLEARING WILL TRANSLATE INTO
COOLER OVERNIGHT LOWS WITH READINGS RUNNING ABOUT 5 DEGREES BELOW
NORMAL.

A RIDGE WILL BUILD OVER THE AREA ON WED AND PERSIST THROUGH WED
NIGHT. WHILE DRIER AIR WILL WORK IN FROM THE SOUTH...SOME MOISTURE
WILL LINGER MAINLY OVER THE NORTH AND MOUNTAINS. MODEL CROSS
SECTIONS INDICATE THAT AN OROGRAPHICALLY FAVORED WEST FLOW WILL
CONTINUE TO PRODUCE SHOWERS OVER THE NORTHERN MOUNTAINS EARLY IN
THE DAY...ESPECIALLY ALONG THE PARK...GORE AND FLATTOPS RANGES.
MOISTURE WILL DIMINISH LATE IN THE DAY THROUGH THE EVENING.
HOWEVER DAYTIME HEATING WILL HELP BOOST AFTERNOON CONVECTION...
AGAIN MAINLY OVER THE MOUNTAINS. BY LATE EVENING THUNDERSTORMS
SHOULD DIE OFF...WITH ONLY A FEW SHOWERS LINGERING BEYOND
MIDNIGHT.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 252 PM MDT TUE MAY 19 2015

THE NEXT LOW PRESSURE SYSTEM RELOADS ALONG THE CENTRAL CA COAST
ON THU. THEN SWINGS INLAND LATE THU NIGHT AND ACROSS THE DESERT
SOUTHWEST/SOUTHERN GREAT BASIN ON FRI/FRI NIGHT. THE RESULTING
SOUTH-SOUTHWEST FLOW WILL BRING ENOUGH MOISTURE FOR SOME DIURNALLY
DRIVEN SHOWERS AND THUNDERSTORMS EACH LATE DAY PERIOD. THE
MOUNTAINS WILL BE FAVORED. ALSO A LEADING DISTURBANCE WILL EJECT
FROM THE PARENT LOW...AND BRUSH THE FORECAST AREA THU EVENING.
THIS WILL PROVIDE A BOOST TO CONVECTION THROUGH THE EVENING...WITH
SHOWERS LINGERING OVERNIGHT.

THERE CONTINUES TO BE SOME DIFFERENCES AT TO THE TRACK OF THE
MAIN LOW PRESSURE TROUGH LATE FRI THROUGH SAT...WITH THE GFS
SLOWER AND FARTHER SOUTH. BUT IT APPEARS THAT A WET WEEKEND IS
AGAIN IN STORE FOR THE AREA. FOR SUNDAY AND BEYOND...THE ECMWF
INDICATES THAT ADDITIONAL AND CLOSELY TIMED LOW PRESSURE
DISTURBANCES WILL PASS OVER THE REGION. THE GFS SHOWS A DISTINCT
RIDGE EARLY IN THE WORK WEEK AFTER THE FIRST LOW EXITS TO THE
EAST...BUT WITH SOME DIURNALLY DRIVEN SHOWERS AND THUNDERSTORMS
EACH LATE DAY PERIOD. THEREFORE THE FORECAST WILL REMAIN UNSETTLED
THROUGH THE END OF THE PERIOD.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 848 PM MDT TUE MAY 19 2015

A FEW SHOWERS WILL LINGER OVER NORTHEAST UTAH AND NORTHWEST
COLORADO THROUGH 14Z...WITH LITTLE TO NO IMPACT EXPECTED AT
TERMINAL SITES. THE SHOWERS WILL OBSTRUCT MOUNTAIN TOPS AT
TIMES...WITH BRIEF MVFR CIGS EXPECTED IN THE VICINITY. ANOTHER
ROUND OF MOUNTAIN CONVECTION IS EXPECTED AFTER 18Z WITH BULK OF
THIS ACTIVITY REMAINING ANCHORED TO THE HIGHER TERRAIN.
OTHERWISE...VFR CONDITIONS ARE EXPECTED THROUGH LATE WEDNESDAY.

&&

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

$$

UPDATE...JDC
SHORT TERM...NL/EH
LONG TERM...EH
AVIATION...JDC



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