Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 270900
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
300 AM MDT SAT SEP 27 2014

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 255 AM MDT SAT SEP 27 2014

LATEST RADAR MOSAIC SHOWS PLENTY OF STORMS AND PRECIP OVER WRN &
CENTRAL UT THIS MORNING. A FEW RETURNS OVER EXTREME SERN UT HAVE
ALSO BEEN SEEN BUT NOTHING OF ANY CONSEQUENCE...YET. HRRR
INITIALIZED EXCEPTIONALLY WELL PICKING UP ON THIS PRECIP OVER UT
AND IF IT`S TO BE BELIEVED...SOME LIGHT PRECIP WILL START OVER ERN
UT BY DAYBREAK OR SHORTLY THEREAFTER WITH MORE WIDESPREAD PRECIP
FIRING FROM NOON ONWARDS. THIS ALSO FOLLOWS BOTH THE NAM AND GFS`S
THINKING SO FORECAST FOLLOWS WITH POPS INCREASING FROM WEST TO
EAST THROUGH THE DAY. AS FAR AS FLOODING PRODUCTS...WILL HOLD OFF
FOR NOW. QPF AMTS THROUGH THE DAY VARY FROM .1 TO .3 INCHES
THOUGH...OF COURSE...ANY CONVECTION COULD INCREASE THESE AMTS
DRASTICALLY IN A SHORT PERIOD OF TIME. WITH SUCH TEPID
AMTS...STRONG CONVECTION MAY CAUSE SOME FLOOD ADVISORIES TO BE
ISSUED BUT WIDESPREAD FLASH FLOODING DOESN`T LOOK LIKELY TO OCCUR
AT THIS TIME. LATEST HPC GUIDANCE ALSO PICKING UP ON THIS KEEPING
EXCESSIVE RAINFALL THREAT OVER WRN UT WITH NO MENTION OF THE
THREAT FOR OUR CWA THROUGH MONDAY MORNING.

OVERNIGHT...PRECIP WILL PICK UP IN INTENSITY FOR MOST OF THE CWA AS
BEST DYNAMICS MOVES OVERHEAD. IF CONVECTION OCCURRING OVER WRN UT
RIGHT NOW IS ANY INDICATION OF WHAT TO EXPECT TONIGHT...PLENTY OF
STORMS AND SHOWERS THAT HAVE FORMED IN THE AFTERNOON WILL CONTINUE
INTO THE OVERNIGHT AND MOVE AT A GOOD CLIP WITH A SPLIT OF SOAKING
RAIN WITH SOME EMBEDDED CONVECTION FOR INCREASED RAINFALL RATES.

TONIGHT INTO SUNDAY...THE CLOSED MID LATITUDE CYCLONE WILL MAKE
LITTLE PROGRESS DURING THIS PERIOD MAINLY STAYING OVER SOUTHERN
NEVADA BEFORE PUSHING TOWARDS THE UTAH STATE LINE LATE SUNDAY. AS
A RESULT THE WARM CONVEYOR BELT SEEN OVER WESTERN UTAH THIS
EVENING WILL ONLY BE MAKING SLOW PROGRESS THROUGH EASTERN UTAH AND
FAR WESTERN COLORADO THE NEXT 24 TO 48 HOURS. POPS ARE ALREADY
HIGH IN THIS REGION AND CONTINUED THIS TREND UPWARD. RAIN
CERTAINLY APPEARS IMMINENT OVER MUCH OF THIS REGION. THE EASTERN
FRINGE OF OUR CWA DOES NOT APPEAR AS FAVORABLE BEING AWAY FROM THE
UPPER LEVEL SUPPORT UNTIL LATER SUNDAY AND DID BACK OFF ON SOME
POPS INCLUDING SOME NORTH FACING VALLEYS AND THE GUNNISON BASIN.
ALSO WITH PWATS MOVING NEAR +2 STD DEVIATIONS ABOVE NORMAL...IT
IS NOT A QUESTION OF IF...BUT HOW MUCH RAIN. THE BULK OF THE
FORCING AND MOISTURE TRANSPORT WILL BE DURING THE OVERNIGHT
HOURS...WITH CLOUD DEBRIS AND PRECIPITATION LIMITING CONVECTIVE
POTENTIAL ON SUNDAY. MODERATE TO HEAVY RAIN WILL BE POSSIBLE WITH
WARM CLOUD DEPTHS FORECAST TO EXCEED 7000 FEET OUR LOWER DESERT
VALLEYS EARLY ON. HOWEVER CONFIDENCE IS STILL WAVERING ON FLASH
FLOOD POTENTIAL...THOUGH WASHES ARE LIKELY TO BE RUNNING IN SOME
AREAS. TEMPS TAKE A HIT BY 10 TO 15 DEGREES SUNDAY.

.LONG TERM...(SUNDAY NIGHT THROUGH FRIDAY)
ISSUED AT 255 AM MDT SAT SEP 27 2014

SUNDAY NIGHT INTO MONDAY...LARGE SCALE ASCENT SHIFTS ACROSS OUR
CWA DURING THIS PERIOD AS THE JET FINALLY ROUNDS THE BASE OF THE
TROF AND MOVES INTO THE PLAINS. THIS WILL INCREASE THE CONDITIONAL
INSTABILITY ALOFT AND WITH A MID LEVEL FRONT PASSING THROUGH
MONDAY...MODERATE TO HEAVY PRECIPITATION WILL BE POSSIBLE EVEN
THOUGH DRIER AIR WILL BE FILTERING IN. THE CONVECTIVE POTENTIAL
DEFINITELY HAS THE POTENTIAL TO LOWER SNOW LEVELS AND DO EXPECT
SOME WHITE TO BE SHOWING UP ABOVE 12000 FEET. HOWEVER AT THIS TIME
DO NOT FEEL PASSES OR TRAVEL WILL BE IMPACTED. TEMPERATURES REMAIN
COOL WITH THE PASSAGE OF THE TROUGH FOR MONDAY AND HIGHS LOOK TO
TOP OUT SOME 7 TO 12 DEGREES BELOW LATE SEPTEMBER NORMALS.

SOME LINGERING SHOWERS POSSIBLE OVER THE NRN CONTINENTAL DIVIDE
TUESDAY BUT BY AND LARGE...PRECIP WILL HAVE ENDED AS COOLER THAN
NORMAL TEMPERATURES PERSIST. A WEAK JET STREAK WILL ALLOW A LOW
AMPLITUDE TROUGH TO FORM AND MOVE OVER THE CWA CAUSING SOME RAIN
AND SNOW AT HIGH ELEVATIONS WED NIGHT INTO THURSDAY MORNING.
PREVIOUS MODEL RUNS DECREASED PRECIP EXTENT WITH THIS DISTURBANCE
WHILE THE 00Z AND 06Z SUBSTANTIALLY INCREASED IT. SNOW LEVELS AT
THIS TIME WILL BE AROUND 10K FEET SO SOME MINOR ACCUMULATIONS
POSSIBLE ABOVE THAT LEVEL. AFTER THAT...HIGH PRESSURE AND
ANTICYCLONIC FLOW SETS UP OVER THE AREA WITH NO PRECIP EXPECTED
WITH TEMPS REMAINING COOL.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 255 AM MDT SAT SEP 27 2014

SHOWERS AND STORMS WILL BE ON THE INCREASE TODAY FIRING OVER ERN
UTAH FIRST AND THEN INCREASING OVER THE REST OF THE CWA FROM 18Z
ONWARDS. FLT CATEGORIES WILL VARY FROM VFR TO IFR BECOMING MORE
MVFR/IFR FROM 21Z ONWARDS AND PERSISTING OVERNIGHT INTO SUNDAY
MORNING. SOME SMALL HAIL IS POSSIBLE TODAY THOUGH STRONG OUTFLOW
WINDS...POSSIBLY EXCEEDING 40MPH...WILL BE THE MAIN CONCERN NEAR
AND UNDER THE STRONGEST CONVECTION. MTNS WILL BE OBSCURED
ESPECIALLY OVERNIGHT. UNSETTLED WX WILL CONTINUE FOR THE NEXT 24
HOURS.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...NONE.
UT...NONE.

&&

$$

SHORT TERM...TGR/15
LONG TERM...15/TGR
AVIATION...TGR


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