Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 121050
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
450 AM MDT SAT APR 12 2014

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 400 AM MDT SAT APR 12 2014

500MB TROUGH AXIS CURRENTLY OVER CALIFORNIA WILL BE PROPELLED EAST
TODAY BY A SECOND UPPER LEVEL TROUGH ORIGINATING FROM BRITISH
COLUMBIA PULLING PACIFIC MOISTURE SOUTHEAST. MID LEVEL CLOUDS WILL
BEGIN TO INCREASE THIS MORNING AND SCATTERED SHOWERS/ISOLATED
TSTORMS ARE EXPECTED TO BEGIN DEVELOPING BY NOON. EXPECTING TSTORM
DEVELOPMENT TO BE VERY ISOLATED TODAY SINCE THERE IS NO LARGE TEMP
GRADIENT FROM THE SFC TO UPPER LEVELS. A VORT MAX EMBEDDED IN
SOUTHWESTERLY FLOW OF THE UPPER LEVEL TROUGH IS MOVING INTO THE FOUR
CORNERS THIS MORNING ACCOMPANIED BY CLOUDS AND A FEW SPRINKLES WHICH
WILL BUILD INTO SCATTERED SHOWERS ACROSS THE MOUNTAINS AS DAYTIME
HEATING OCCURS. WITH CLOUD THICKNESS FAIRLY THIN THIS
MORNING...SHOWER DEVELOPMENT IS EXPECTED TO BE EFFICIENT TODAY OVER
THE MOUNTAINS BUT FOR THE MOST PART STAY OUT OF THE VALLEYS UNTIL
LATER TODAY THOUGH THE POSSIBILITY IS STILL THERE.

SHOWERS ARE EXPECTED TO TAPER OFF SLIGHTLY TONIGHT BEFORE RAMPING UP
AGAIN EARLY SUNDAY MORNING WITH A PRETTY IMPRESSIVE SHORTWAVE/UPPER
LEVEL TROUGH MOVING INTO THE GREAT BASIN. PWAT VALUES INCREASE TO
0.50 INCH IN SOME AREAS SUNDAY MORNING WHICH IS RATHER HIGH FOR THIS
TIME OF YEAR. SNOW LEVEL IS EXPECTED TO BEGIN AROUND 9000 FEET
SATURDAY NIGHT AND DROP TO NEAR VALLEY LEVEL AROUND SUNSET ON
SUNDAY. MODELS SHOW LOW PRESSURE CENTER FROM SFC TO UPPER LEVELS
WHICH IS INDICATIVE OF A WELL ORGANIZED SYSTEM. THAT BEING
SAID...THIS SYSTEM WILL MOVE THROUGH PRETTY QUICKLY THROUGHOUT THE
DAY SUNDAY. UPGRADED WINTER STORM WATCHES TO WINTER WX ADVISORIES
AS MOST LOCATIONS ABOVE THE SNOW LINE SHOULD STAY IN THE 6 TO 10
INCH RANGE WITH THE FAST MOVING NATURE OF SYSTEM AND PRETTY LOW
WATER TO SNOW RATIOS DURING THE MAJORITY OF THIS EVENT. COULD BE
AN ISOLATED 12+ INCH READING BUT WITH CONVECTIVELY DRIVEN SNOWFALL
INTENSITY...THIS WILL BE TOUGH TO PINPOINT. ADDED SAN JUANS TO
ADVISORIES WITH CENTER OF LOW PRESSURE HEADING OVERHEAD THAT AREA
AND GOOD MOISTURE TO AFFECT PASSES.

KEPT CO VALLEY ZONES OUT OF ADVISORIES FOR NOW BUT MAY NEED TO BE
LOOKED AT AGAIN TODAY TO SEE WHERE 12Z MODELS PROG FRONTAL FORCING.
VALLEYS WILL DEFINITELY START PRECIPITATING AS RAIN AND AM EXPECTING
MOST OF THE PRECIP TO FALL AS RAIN IN THE VALLEYS. BY THE TIME COLD
AIR SURGES INTO THE AREA...DRIER AIR WILL ALSO BE ENTRAINING INTO
THE REGION.

.LONG TERM...(SUNDAY NIGHT THROUGH FRIDAY)
ISSUED AT 400 AM MDT SAT APR 12 2014

THE SHORT AND MIDRANGE MODELS HAVE BEEN CONSISTENT FOR THE PAST
TWO NIGHT FROM RUN TO RUN AND BETWEEN EACH MODEL SOLUTION
CONCERNING THIS WEEKENDS STORM AND THE BEGINNING OF NEXT WEEK.
SUNDAY EVENING WILL SEE THE STRONG TROUGH MENTIONED ABOVE MOVING
STEADILY FROM NORTH TO SOUTH THROUGH THE FORECAST AREA. THE NAM12
AND GFS ARE ABOUT 3-6 HOURS FASTER IN MOVING THE TROUGH THROUGH...
WITH THE MAIN TROUGHLINE MOVING OUT OF THE AREA TO THE SOUTHEAST
BETWEEN 06 AND 09Z SUN NGT/YON MORNING. THE ECMWF DOESN`T HAVE
THE TROUGH IN THAT POSITION UNTIL ABOUT 12Z. THROUGHOUT THE SUNDAY
NIGHT THE FLOW AT MOUNTAINTOP LEVEL WILL BE NORTHWESTERLY AND
BECOMING MORE NORTHERLY. THIS WIND DIRECTION IS A GOOD OROGRAPHIC
SNOWFALL DIRECTION FOR ONLY A FEW ZONES AND AREAS...THE NORTHERN
FLATTOPS...PORTIONS OF THE CENTRAL MOUNTAINS AND THE NORTHWEST SAN
JUAN MOUNTAINS INCLUDING THE GORGE FROM SOUTH OF MONTROSE TO
OURAY. THE WINTER WEATHER ADVY WILL BE IN EFFECT UNTIL 3 AM MDT AS
A RESULT...AND POPS WERE BOOSTED IN THE APPROPRIATE ZONES.

EACH MODELS SHOWS A DRY MONDAY AND TUESDAY...WITH NORTHWEST FLOW
DOMINATING. FOLLOWING THIS THERE IS GREAT DISCONTINUITY IN THE
SOLUTIONS FOR THE NEXT STORM SYSTEM. THE GFS BRINGS ANOTHER
DIGGING PACNW TROUGH THROUGH THE AREA WED NGT AND THU...WHILE THE
ECMWF BRINGS THROUGH A MUCH LESS DEVELOPED FEATURE IN THE FORM OF
TWO WEAKER SHORTWAVES WITH LESS MOISTURE AND DYNAMICS

FRIDAY APPEAR WILL BE AN IN-BETWEEN DAY AS EACH MODEL CONTINUES
WILL A SOMEWHAT ZONAL FLOW WITH WEAK EMBEDDED SHORTWAVES AS
ANOTHER LOW STRENGTHENS WELL OVER THE WEST COAST.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 400 AM MDT SAT APR 12 2014

LAYERED MIDDLE AND HIGH CLOUD WILL SPREAD ACROSS THE FORECAST
AREA TODAY. ISOLD TO SCTD SHOWERS AND A FEW THUNDERSTORMS ARE
EXPECTED THIS AFTERNOON AND EVENING...WITH A 10 TO 20 CHANGE OF A
THUNDERSTORM IN THE VICINITY OF ALL AIRPORTS AND TAF SITES. THE
SHOWERS AND TSTMS WILL OCCASIONALLY OBSCURE THE MOUNTAINS AND HIGH
PASSES. A STRONGER STORM WILL EFFECT THE AREA TONIGHT...BRINGING
WIDESPREAD SNOWFALL TO ALL THE MOUNTAINS AND FREQUENTLY OBSCURED
MOUNTAINS AND PASSES AFTER 06Z. MVFR CONDITIONS IN SHOWERS AND
LOWER CLOUDS ARE MOST POSSIBLE OVER KCAG...KHDN...KSBS...
KASE...AND KEGE

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER WEATHER ADVISORY FROM 6 AM SUNDAY TO 3 AM MDT MONDAY FOR
     COZ004-009-010-012-013-018-019.

UT...NONE.
&&

$$

SHORT TERM...JAM
LONG TERM...CC
AVIATION...CC



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