Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 220424
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1024 PM MDT SUN SEP 21 2014

.SHORT TERM...(TONIGHT THROUGH MONDAY NIGHT)
ISSUED AT 338 PM MDT SUN SEP 21 2014

THE SOUTHWEST LOW HAS LIFTED NORTHEAST ACROSS NV TODAY...AND WILL
MOVE INTO SOUTHWEST ID BY AROUND MIDNIGHT. AHEAD OF THE
LOW...THIS MORNING`S AREA OF SHOWERS HAVE MOVED OVER THE NORTHEAST
CORNER OF THE FORECAST AREA AND SHOULD BE EXITING TO THE NORTHEAST
IN THE NEXT HOUR OR SO. OF MORE INTEREST...ONE SHORTWAVE ROTATING
AROUND THE EAST SIDE OF THE LOW HAS PRODUCED AN ENERGETIC BAND OF
CONVECTION THAT HAS MOVED INTO SOUTHEAST/EAST-CENTRAL UTAH. FOR
UPPER LEVEL SUPPORT THE NOSE OF A SPEED ROTATED ACROSS SOUTHWEST
UTAH TODAY...AND POINTED RIGHT AT EAST CENTRAL UT THIS AFTERNOON.
THE SOUTH-NORTH ORIENTED CONVECTIVE BAND HAS BEEN MOVING EAST-
NORTHEAST AROUND 25 MPH...WITH INDIVIDUAL CELLS WITHIN THE BAND
TRACKING TO THE NORTH-NORTHEAST. SOME OF THESE STORMS HAVE
PRODUCED BRIEF HEAVY RAIN...SMALL HAIL AND WIND GUSTS IN EXCESS OF
45 MPH. THIS BAND WILL CONTINUE TO TRACK ACROSS THE AREA... AND
WILL MOVE INTO NORTHEAST UTAH...AND WEST-CENTRAL TO NORTHWEST
COLORADO THROUGH THE EARLY EVENING. DO NOT EXPECT THAT THESE
STORMS WILL CREATE MUCH IN THE WAY OF RUNOFF PROBLEMS DUE TO
THEIR SPEED...BUT ISOLATED WIND GUSTS MAY APPROACH 50 MPH.

THE NAM PEGGED THE HEAVIER SHOWERS OVER SOUTHWEST COLORADO LAST
NIGHT...WHERE FLOODING WAS REPORTED IN AND AROUND DURANGO. FOR
TONIGHT...SEVERAL RUNS OF THE NAM HAVE AGAIN CONSISTENTLY
INDICATED GOOD QPF WILL DEVELOP IN THE SAME AREA. THEREFORE
SHOWERS AND THUNDERSTORMS SHOULD INCREASE ALONG THE SOUTHERN
SLOPES OF THE SAN JUANS TO THE NEW MEXICO BORDER THIS
EVENING...AND CONTINUE OVERNIGHT. THE NAM SHOWS PWAT VALUES
AROUND 1.25 INCHES IN THE 4-CORNERS AT MIDNIGHT...WITH A
CONTINUED OROGRAPHICALLY FAVORED FLOW THROUGH THE NIGHT. SINCE
SOILS ARE ALREADY SATURATED IN THE THIS AREA...ADDITIONAL
FLOODING IS POSSIBLE. THEREFORE THE FLASH FLOOD WATCH FOR THAT
AREA IS STILL ON TRACK. OF NOTE...SNOW WAS REPORTED ABOVE AROUND
10-11K FT IN THE SAN JUANS THIS MORNING. THEREFORE THE HIGHER
COLORADO MOUNTAINS...AND UINTAS OF NORTHEAST UTAH SHOULD SEE A
DUSTING BY MORNING.

BY EARLY MONDAY THE CENTER OF THE LOW WILL SHIFT INTO WESTERN WY
WITH THE TROUGH AXIS TRACKING ACROSS THE FORECAST AREA THROUGH
THE DAY. THIS WILL RESULT IN A DRIER WEST FLOW...WITH SHOWERS
DECREASING FROM THE WEST TO EAST. THE NORTH WILL SEE THE BETTER
LARGE SCALE SUPPORT AS THAT AREA IS IN BETTER PROXIMITY TO THE
UPPER LOW. SO ACTIVITY SHOULD LINGER THERE LONGEST. ONCE THE
TROUGH AXIS MOVES TO OUR EAST...AND DAYTIME HEATING SUBSIDES ANY
LINGERING ACTIVITY WILL QUICKLY DIMINISH. HOWEVER EXPECT SOME
SHOWERS TO LINGER ALONG THE NORTHERN DIVIDE THROUGH THE LATE
EVENING.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 338 PM MDT SUN SEP 21 2014

HIGH PRESSURE AMPLIFIES OVER THE GREAT BASIN ON TUESDAY AND
PROGRESSES OVERHEAD WEDNESDAY INTO THURSDAY. DAYTIME TEMPERATURES
WILL CLIMB FIVE OR MORE DEGREES ABOVE NORMAL WHILE OVERNIGHT LOWS
WILL BE NEAR NORMAL. NORTHWEST GRADIENT WINDS TUESDAY WILL BECOME
MOSTLY TERRAIN DRIVEN WEDNESDAY AND THURSDAY. A WEAK SURGE OF
MOISTURE ASSOCIATED WITH A BACKDOOR COOL FRONT MAY PRODUCE SOME
THUNDERSTORMS AND SHOWERS IN THE EASTERN PORTION OF THE SAN JUANS
LATE THURSDAY.

OTHERWISE THE NEXT PACIFIC TROUGH SPLITS ALONG THE WEST COAST
FRIDAY IN THE GFS OR SATURDAY IN THE EC. BOTH MODELS CLOSE THIS
LOW OVER THE DESERT SW WITH THE GFS CONSISTENTLY PRODUCING A
FASTER PROGRESSION INLAND. BOTH MODELS PULL DEEP MOISTURE INTO
THE REGION NEXT WEEKEND...STARTING FRIDAY IN THE GFS AND SATURDAY
IN THE EC. THIS STORM IS FORECAST TO HAVE A STRONGER COLD CORE
THAN WE HAVE SEEN SO FAR THIS SEASON. 700MB TEMPERATURES DROP TO
-2C WOULD THREATEN SNOWFALL DOWN TO AROUND 8000 FEET. BUT ALL
STORM DETAILS HAVE LOW CONFIDENCE THIS FAR OUT.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1024 PM MDT SUN SEP 21 2014

A STRONG CLOSED LOW PRESSURE SYSTEM CENTERED OVER NEVADA WILL
CONTINUE TO DRAW SUBTROPICAL MOISTURE OVER THE REGION TONIGHT. AS
A RESULT...EXPECT SHOWERS AND THUNDERSTORMS TO REMAIN WIDESPREAD
OCCASIONALLY IMPACTING TAF SITES THROUGHOUT THE REGION. MVFR CIGS
AND VSBY...AND IN SOME CASES...BRIEF IFR CONDITIONS ARE POSSIBLE
IN HEAVY RAIN. MOUNTAINS WILL BE OBSCURED AT TIMES AND GUSTY AND
UNPREDICTABLE OUTFLOW WINDS TO 45 MPH WILL EMANATE FROM THE
STRONGER CELLS. AS THE LOW LIFTS OVER WYOMING ON MONDAY...DRIER
AIR WILL BEGIN TO FILTER INTO THE REGION CAUSING SHOWER AND STORM
ACTIVITY TO BECOME MORE SCATTERED IN COVERAGE BEFORE DIMINISHING
DURING THE EVENING.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...FLASH FLOOD WATCH UNTIL 9 AM MDT MONDAY FOR COZ019-022-023.

UT...NONE.

&&

$$

SHORT TERM...EH
LONG TERM...JOE
AVIATION...NL



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