Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 211627
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1027 AM MDT SUN SEP 21 2014

.UPDATE...
ISSUED AT 1027 AM MDT SUN SEP 21 2014

MODELS CONTINUE TO SHOW ANOTHER GOOD SURGE OF PRECIPITATION INTO
THE SOUTHWEST SAN JUANS...AND THE DURANGO AREA THIS EVENING AND
OVERNIGHT. AFTER ASSESSING THE FLOODING THAT TOOK PLACE IN THE
DURANGO AREA LAST NIGHT...HAVE DECIDED TO HOIST A FLASH FLOOD
WATCH FOR THE SOUTHWEST SAN JUANS TO THE NEW MEXICO BORDER...AND
FROM THE MANCOS RIDGE EASTWARD TO THE PAGOSA SPRINGS AREA. FEEL
THAT EVEN MODEST AMOUNTS OF RAINFALL COULD CAUSE PROBLEMS IN
AREAS WHERE FLOODING HAS ALREADY OCCURRED...OR WHERE SOILS ARE
SATURATED.

OTHERWISE...HAVE MADE A FEW MODIFICATIONS TO TODAYS FORECAST TO
ADD SOME SPACIAL DETAILS. THE MAIN BAND OF PRECIPITATION HAS
MOVED OVER THE NORTHERN HALF...AND WILL CONTINUE TO TRACK
NORTHWARD. THE NORTH SHOULD SEE THE BETTER COVERAGE OF SHOWERS
AND THUNDERSTORMS THIS AFTERNOON. LOOKS LIKE THE SOUTH WILL
CONTINUE TO SEE A BREAK OF SORTS UNTIL LATE THIS AFTERNOON...
WITH THE HEAVIEST PRECIPITATION DEVELOPING AROUND MIDNIGHT.

&&

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 356 AM MDT SUN SEP 21 2014

CLOSED LOW OVER CALIFORNIA WILL MOVE EAST INTO NEVADA AND ALLOW
MOIST SOUTHWEST FLOW TO SPREAD OVER THE AREA. MODEL FORECASTED
PRECIPITABLE WATER VALUES WILL CLIMB TO 1.1 INCHES OVER THE
FORECAST AREA TODAY. MODELS ARE SHOWING A WEAK WAVE MOVING THROUGH
SOUTHERN SECTIONS THIS MORNING WITH LIGHT TO MODERATE RAIN
OCCURRING SOUTH OF HIGHWAY 50. HEAVIER PRECIPITATION WITH
ASSOCIATED FLOODING HAS BEEN REPORTED IN THE DURANGO AREA WITH
RADAR UNDERESTIMATING PRECIPITATION AMOUNTS AT THIS RANGE. EXPECT
THIS BAND OF PRECIPITATION TO MOVE NORTHEAST THROUGH THE MORNING
HOURS. GUSTY OUTFLOW WINDS TO 40 MPH CAN BE EXPECTED DURING THE
ONSET OF PRECIPITATION. MODELS ARE INDICATING A LULL IN THE
ACTIVITY LATER THIS MORNING BEFORE ANOTHER WEAK WAVE COMBINES WITH
AFTERNOON HEATING THIS AFTERNOON TO KICK OFF ANOTHER ROUND OF
CONVECTION. EXPECT SHOWER AND THUNDERSTORM ACTIVITY TO BECOME MORE
WIDESPREAD LATER THIS AFTERNOON WITH SOME LOCALLY HEAVY RAIN AND
SMALL HAIL POSSIBLE WITH THE STRONGER STORMS.

TONIGHT AND MONDAY...LARGE SCALE ASCENT INCREASES OVER OUR CWA
OVERNIGHT AS THE MAIN UPPER LOW SHIFTS NORTHEAST FROM THE GREAT
BASIN TO THE NORTHERN HIGH PLAINS. THE UPWARD MOTION CAN BE
ATTRIBUTED FROM A JET MAX ROUNDING THE BASE OF THE OF THE LOW AND AN
AREA OF DIFFLUENT FLOW ALOFT. PWAT REMAINS HIGH AND CONDITIONAL
INSTABILITY SHOULD BE INCREASING OVERNIGHT AS THE DYNAMIC TROP
LEVEL LOWERS WITH THE ARRIVAL OF THE JET. POPS SEEMED WELL HANDLED
AND IN LINE WITH THE LATEST GUIDANCE SO NO MAJOR CHANGES. DRYING
ASSOCIATED WITH SUBSIDENCE AND ADVECTION FROM THE SOUTHWEST WILL
BRING A DOWNTURN IN THE PRECIPITATION THROUGH THE DAY ON MONDAY.
CONVECTION STILL LIKELY TO POP IN THE AFTERNOON BUT BE LIMITED TO
THE TO THE EASTERN MOUNTAINS. TEMPERATURES COOL BEHIND THE WAVE IN
THE NORTHERLY FLOW BUT STILL END UP CLOSE TO NORMAL.

.LONG TERM...(MONDAY NIGHT THROUGH SATURDAY)
ISSUED AT 356 AM MDT SUN SEP 21 2014

MONDAY NIGHT AND TUESDAY...DRY NORTHWEST FLOW WILL DOMINATE THIS
PERIOD AS RIDGING BUILDS ACROSS THE WEST. TEMPERATURES WILL BE
WARMING AS A RESULT OF THE DRIER AIR AND HIGHS WILL BE PUSHING BACK
TO AROUND 5 DEGREES ABOVE NORMAL.

RIDGE OF HIGH PRESSURE OVER THE GREAT BASIN ON WEDNESDAY WILL
SHIFT EAST OVER THE GREAT LAKES REGION BY THE END OF THE WORKWEEK
AS A BROAD TROUGH IMPACTS THE PACIFIC NORTHWEST. EXPECT DRY AND
UNSEASONABLY WARM CONDITIONS WEDNESDAY THROUGH FRIDAY WITH
AFTERNOON TEMPERATURES RUNNING ABOUT 10 DEGREES ABOVE NORMAL. THE
LONG RANGE FORECAST FOR NEXT WEEKEND SHOWS A DEEP TROUGH MOVING
INTO THE GREAT BASIN WITH AN UNSETTLED WEATHER PATTERN EXPECTED
OVER THE FORECAST AREA. GFS CURRENTLY IS A BIT QUICKER AND MORE
NORTH WITH TRACK THAN THE SLOWER ECMWF SOLUTION. CONFIDENCE IS
CURRENTLY LOW ON EXACT TRACK AND TIMING OF THIS SYSTEM SO KEEP
TRACK OF SUBSEQUENT FORECASTS FOR FURTHER UPDATES.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 356 AM MDT SUN SEP 21 2014

SHOWERS AND THUNDERSTORMS WILL CONTINUE TO MOVE NORTH ACROSS SOUTHWEST
COLORADO AND SOUTHEAST UTAH THROUGH THE EARLY MORNING HOURS. GUSTY
OUTFLOW WINDS TO NEAR 40KT ARE POSSIBLE AT THE ONSET. SCATTERED
SHOWERS AND STORMS WILL DEVELOP BY 18Z SUNDAY WILL BECOME MORE
WIDESPREAD BY MID-AFTERNOON WITH SHOWERS PRODUCING VISIBILITIES
DOWN TO 4SM AND CEILINGS AT OR BLO 040 WELL INTO THE EARLY MORNING
HOURS ON MONDAY. MTN TOPS WILL BE OBSCURED AT TIMES AND ALL TAF
SITES CAN EXPECT BRIEF MVFR CIGS AND VSBY FROM 18Z SUNDAY TO 10Z
MONDAY.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...FLASH FLOOD WATCH FROM 6 PM MDT THIS EVENING THROUGH MONDAY
     MORNING FOR COZ019-022-023.

UT...NONE.
&&

$$

UPDATE...EH
SHORT TERM...MPM/15
LONG TERM...15/MPM
AVIATION...MPM



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