Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 262301
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
501 PM MDT SUN OCT 26 2014

.UPDATE...
ISSUED AT 448 PM MDT SUN OCT 26 2014

AS THE LEFT EXIT REGION OF A JET STREAK BEGIN TO RIDE OVER CENTRAL
AND NORTHWEST COLORADO CONVECTION KICKED INTO GEAR. ISOLATED
THUNDERSTORMS WILL INCREASE OVER NORTHEAST UT AND NORTHWEST CO
THIS EVENING...WITH THE HIGHER AND LOWER ELEVATIONS BEING
AFFECTED. HAVE INCREASED THE CHANGE OF RAIN IN THE POP GRIDS AND
UPDATED THE ZFP.

&&

.SHORT TERM...(TONIGHT THROUGH MONDAY NIGHT)
ISSUED AT 244 PM MDT SUN OCT 26 2014

THE FIRST BATCH OF MOISTURE MOVED OVER WESTERN COLORADO UNEVENTFULLY
THIS MORNING BUT HOPEFULLY HAS PRIMED TO PUMP FOR THE MAIN SYSTEM
ARRIVING THIS EVENING. PREFRONTAL SOUTHWEST WINDS HAS LED TO GOOD
MIXING AND TEMPERATURES SPIKED ABOVE THOSE EXPECTED EARLIER. ALL
THIS TALK OF WARM WEATHER WILL UNFORTUNATELY BE IN THE PAST AS A
COLD FRONT CURRENTLY ANALYZED OVER NORTHWEST UTAH SLAMS THROUGH
OUR CWA THIS EVENING AND OVERNIGHT. SHOWERS AND AN ISOLATED
THUNDERSTORM WILL BE POSSIBLE AHEAD OF AND WITH FROPA THIS
EVENING...WITH THE CONVECTION BOOSTING QPF AMOUNTS AND LOWERING
SNOW LEVELS. RADAR RETURNS ARE NOT ROBUST ATTM BUT DO SIGNAL THE
CONDITIONAL INSTABILITY READY TO BE RELEASED. THIS SHOULD OCCUR AS
THE UPPER LEVEL FORCING INCREASES AHEAD OF A NORTHERN ROCKIES
SYSTEM PASSES BY AND ENHANCED BY A JET MAX SCOOTING ACROSS
NORTHWEST COLORADO THIS EVENING. THE DIRECT CIRCULATION OF THIS
JET WILL BE FAVORABLE FOR MID LEVEL FRONTOGENESIS ENHANCE LIFT
ALONG WITH LOW LEVEL FORCING FROM THE COLD FRONT. ALL THIS SOUNDS
GOOD FOR DECENT QPF AS PWAT IS RUNNING JUST ABOVE NORMAL...HOWEVER
CONFIDENCE IS LOWER TOWARDS PTYPE EARLY IN THE EVOLUTION THIS
EVENING. THE FRONT WILL BRING COOLER AIR TO THE NORTH AND LARGE
SCALE LIFT IS THOUGH A SATURATED DENDRITIC LAYER. AM BANKING ON
THIS AND CONVECTION HELPING TO LOWER SNOW LEVEL DURING PRIME TIME.
ANOTHER MID LEVEL FRONT ALSO PASSES THROUGH DURING THE EARLY
MORNING HOURS AND WILL BE LOWERING H7 TEMPS AND SHOULD HELP SNOW
ACCUMULATE. MOST OF THE ACCUMULATION WILL BE OVER THE PEAKS BUT
WITH SUCH A HUGE CHANGE FROM FALL TO WINTER IN THE HIGH COUNTRY
DECIDED TO HOIST AN ADVISORY OVER THE NORTHERN MOUNTAINS AND
PASSES. THE ROADWAYS MAY STAY WET FOR A WHILE BUT THE SECOND SHOT
OF COLDER AIR IS LIKELY TO BRING ICY CONDITIONS BY SUNRISE.
ACCUMULATIONS OF 2 INCHES OR LESS EXPECTED ACROSS THE MOUNTAIN
VALLEYS ALONG AND NORTH OF I-70. THE ELKS AND SAN JUANS WILL SEE A
BIT OF SNOW WITH THE FROPA BUT LARGE SCALE FORCING IS LACKING TO
THE SOUTH.

THERE IS A TRAILING WAVE AND SHOT OF INSTABILITY IN THE MID TO LATE
MORNING HOURS WHICH MAY BRING ANOTHER SHOT OF LIGHT SNOW BUT
CONFIDENCE NOT TO HIGH ON THIS SO ADVISORIES END BY 9 AM OR SOONER.
THE BIG SHOCK WILL BE THE COLD AIR SPILLING IN BEHIND THE FRONT.
TEMPERATURES TO OUR NORTH ARE IN THE 40S AND 50S AND WITH SOME
MODIFICATIONS HIGHS ON MONDAY LOOK AROUND 15 TO 20 DEGREES COLDER
THAN TODAY. THIS SETS THE STAGE FOR A COLD NIGHT GOING INTO SUNRISE
TUESDAY. GUIDANCE STILL TRENDING A BIT LOWER IN THE MET AND RANGES
FROM 26 TO 32 AT GJT. THE ONLY CONCERN ATTM IS ANOTHER PASSING WAVE
IN THE NORTHWEST FLOW IS BRINGING A BATCH OF HIGH LEVEL CLOUDINESS
INTO WESTERN COLORADO AND EASTERN UTAH AFTER MIDNIGHT.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 244 PM MDT SUN OCT 26 2014

THE REMAINDER OF THE WORK WILL BE DRY WITH MODERATING
TEMPERATURES. UPPER LEVEL NORTHWEST FLOW WILL DOMINATE OVER THE
REGION TUESDAY THROUGH THURSDAY IN ADVANCE OF AN AMPLIFYING UPPER
LEVEL RIDGE. WILL HAVE VARYING AMOUNTS OF HIGH LEVEL CLOUDS
THROUGH THIS PERIOD AND TEMPERATURES WILL WARM 3 TO 5 DEGREES EACH
DAY...GETTING BACK TO AROUND 10 DEGREES ABOVE SEASONAL NORMS BY
THURSDAY. LONG RANGE MODELS IN AGREEMENT WITH SHARP UPPER LEVEL
RIDGE AXIS OVER THE ROCKIES THURSDAY NIGHT...THEN SLIDING EAST
FRIDAY AS A STRONG TROUGH APPROACHES THE WEST COAST. WE TRANSITION
TO SOUTHWESTERLY FLOW FRIDAY AND THIS WILL BE THE WARMEST DAY OF
THE WEEK BEFORE IMPACTS OF THE APPROACHING TROUGH AFFECT US OVER
THE WEEKEND. HIGH TEMPS ON FRIDAY COULD APPROACH RECORD LEVELS.

UPPER LEVEL DIFFLUENT FLOW DEVELOPS OVER ERN UT AND WRN CO BY
SATURDAY ALONG WITH INCREASING MOISTURE. WILL SEE CHANCE OF
SHOWERS INCREASING THROUGH THE DAY AND PEAK SATURDAY NIGHT INTO
SUNDAY MORNING IF THE CURRENT TIMING HOLDS...WITH RESIDUAL
OROGRAPHIC SHOWERS CONTINUING THROUGH SUNDAY OVER THE HIGHER
TERRAIN AND NEAR THE DIVIDE. AT THIS TIME MODELS TAKE THE CORE
UPPER LEVEL FORCING AND COLDEST AIR FROM NRN UT INTO WYOMING WITH
A WEAKER LOBE OF FORCING SPLITTING OFF AND GOING OVER SRN CO
SUNDAY. SO WHILE THE WEEKEND LOOKS UNSETTLED...IT IS LOOKING LIKE
ONLY MINOR IMPACTS OF WIND/SNOW FOR THE HIGHER ELEVATIONS AND ONLY
LIGHT RAIN POSSIBLE AT THE LOWER ELEVATIONS. TEMPS WILL FALL BACK
TO NEAR OR SLIGHTLY BELOW NORMAL FOR SUNDAY INTO MONDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)
ISSUED AT 448 PM MDT SUN OCT 26 2014

VFR CONDITIONS WILL PERSIST AT ALL TAF SITES SOUTH OF A LINE FROM
ABOUT GREEN RIVER TO GUNNISON. SCATTERED SHOWERS AND A FEW
THUNDERSTORMS WILL AFFECT NORTHEAST UT AND NORTHWEST CO NORTH OF
THAT LINE...CAUSED BY A COLD FRONT MOVING OVER THE AREA. MOUNTAIN
OBSCURATION WILL INCREASE NORTH OF THE GREEN RIVER TO GUNNISON
LINE AND KASE WILL EXPERIENCE RAIN AND SNOW SHOWERS...THOUGH
CONDITIONS SHOULD REMAIN VFR.

AFTER ABOUT 06Z LOWER CIGS AND SNOW SHOWERS APPEAR POSSIBLE AT
KASE AND KTEX AS THIS FRONT MOVES THROUGH AFTER ABOUT 09Z AND
WINDS SHIFT TO THE NORTH. MOUNTAIN MECHANICAL TURBULENCE IS
EXPECTED THROUGH THE FORECAST PERIOD WITH STRONGER WINDS ALOFT
AND INVERSION LAYERS NEAR MOUNTAIN TOP LEVEL. CONDITIONS WILL
IMPROVE AFTER 18Z MONDAY.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 9 AM MDT
     MONDAY FOR COZ004-010-013.

UT...NONE.
&&

$$

UPDATE...CC
SHORT TERM...15
LONG TERM...BEN
AVIATION...CC



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