Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 301706
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1106 AM MDT TUE SEP 30 2014

.UPDATE...
ISSUED AT 1048 AM MDT TUE SEP 30 2014

FORECAST LOOKS ON TRACK FOR THE MOST PART AS A COUPLE OF EMBEDDED
WAVES PASS OVER THE AREA TODAY. BOTH OF THESE DISTURBANCES WILL
AFFECT MAINLY THE NORTHERN HALF OF THE FORECAST AREA. THE FIRST
WAVE HAS RESULTED IN SOME SHOWERS OVER THE CENTRAL TO EAST I-70
CORRIDOR AND NORTHWARD THIS MORNING. THE LEADING EDGE OF THE NEXT
WAVE HAS MOVED INTO NORTHEAST UTAH IN THE LAST HOUR OR SO...AND
WILL BE A BIGGER PLAYER THIS AFTERNOON. THEREFORE EXPECT AN
INCREASE IN SHOWERS...WITH SOME THUNDERSTORMS DURING THE EARLY
AFTERNOON HOURS.

&&

.SHORT TERM...(TODAY THROUGH WEDNESDAY)
ISSUED AT 405 AM MDT TUE SEP 30 2014

BROAD CYCLONIC FLOW COVERS THE WRN STATES WITH AN EMBEDDED SHORT
WAVE MOVING ACROSS WRN COLORADO THIS AFTERNOON. THIS WILL TRIGGER
ANOTHER ROUND OF SHOWERS AND STORMS...MOSTLY ACROSS THE NORTH AS
THE AIR MASS IS DRIER ACROSS THE SOUTH. PRECIPITABLE WATER IS
LOWER TODAY...OR THE DEEP MOIST LAYER IS NOT AS PREVALENT. SHOWERS
AND STORMS WILL BE WEAKER THIS AFTERNOON. WITH DECENT GRADIENT
WESTERLY FLOW...RAP13 AND NAM MODELS SHOWING THAT SHOWERS WILL BE
CONCENTRATED OVER THE NRN HIGH COUNTRY. SHOWERS WILL BE LESS
NUMEROUS SOUTH OF THE I70 CORRIDOR.

TONIGHT ONE WEAK DISTURBANCE EXITS EAST BUT THE NEXT STRONGER
NORTHERN PACIFIC WAVE DIVES THROUGH THE NORTHERN GREAT BASIN
OVERNIGHT. MODELS HAVE CONSISTENTLY SHOW SOME FORCING ACROSS THE
NORTH OVERNIGHT FOR SHOWERS THROUGH THE NIGHT. INSTABILITY IS
LIMITED SO LIGHTNING WILL BE ISOLATED IF AT ALL. DRY CONDITIONS
ARE EXPECTED THROUGH THE NIGHT SOUTH OF THE I-70 CORRIDOR THOUGH
SHOWERS WILL BEGIN TO SPREAD SOUTH TOWARDS SUNRISE.

WEDNESDAY THERE IS STILL SOME SLIGHT TIMING DIFFERENCE IN THE
MODELS. THE POLAR FRONT JET STRETCHES ALONG THE CO-NM STATE LINE
WITH THE SURFACE FRONT INDICATING THE TROUGH WILL IMPACT NEARLY
ALL OF THE FORECAST AREA. THE COLD FRONT WORKS INTO NE UT-NW CO
EARLY IN THE MORNING AND WORKS QUICKLY SOUTH OF I-70 BY NOON AND
THROUGH THE SOUTH IN THE AFTERNOON. THE BEST COLD ADVECTION...
MOISTURE AND FORCING OVER NW COLORADO WILL PRODUCE THE HEAVIEST
SHOWERS THERE. THE COLD ADVECTION IS THE STRONGEST OF THE SEASON
SO FAR. A -20C COLD CORE OVER THE NORTH WILL LIKELY LOWER SNOW
LEVELS TO AROUND 8KFT IN THE AFTERNOON. THE DOWNSIDE OF THIS STORM
IS LIMITED INSTABILITY AND A LACK OF A GOOD MOISTURE TAP.

.LONG TERM...(WEDNESDAY NIGHT THROUGH MONDAY)
ISSUED AT 405 AM MDT TUE SEP 30 2014

COLD ADVECTION CONTINUES ACROSS THE CWA OVERNIGHT. FLOW VEERS TO
NNW FAVORING NORTH-FACING SLOPES WITH SNOW. THE FIRST WINTER
HIGHLIGHTS OF THE SEASON STILL LOOK POSSIBLE FOR THE NORTHERN AND
CENTRAL MTNS AND PERHAPS THE COLORADO NORTHERN HIGH VALLEYS WITH
THE FIRST SIGNIFICANT ACCUMULATIONS OF THE COOL SEASON. SNOW
LINGERS ALONG THE COLORADO SPINE INTO THURSDAY MORNING BUT SHOULD
END BY AROUND SUNRISE. FREEZING TEMPERATURES ARE POSSIBLE IN
THE NORTHERN VALLEYS...THE ROARING FORK VALLEY...AND PERHAPS EVEN
INTO DURANGO-PAGOSA.

THURSDAY WILL BE DRY BUT WITH DAYTIME TEMPERATURES 5-10 DEGREES
BELOW NORMAL. ANOTHER COLD NIGHT IS IN STORE THURSDAY NIGHT WITH
ALL BUT THE LOWEST VALLEYS THREATENED WITH FREEZING TEMPERATURES.

DRY WEATHER EXPECTED THROUGH THE PERIOD GIVEN HIGH PRESSURE
COVERING THE SWRN CONUS. MAIN WESTERLY JET STAYS WELL NORTH OF
COLORADO AND ALLOWS TEMPS TO REBOUND TO A FEW DEGREES ABOVE
CLIMATOLOGY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1106 AM MDT TUE SEP 30 2014

SHOWERS WILL INCREASE THIS AFTERNOON ALONG THE MIDDLE TO EAST I-70
CORRIDOR AND NORTHWARD THIS AFTERNOON...WITH SOME THUNDERSTORMS
DEVELOPING BY AFTER 19Z. AT TIMES MOUNTAINS WILL BE OBSCURED IN
LOW CLOUDS AND PRECIPITATION. IFR WILL DOMINATE AT AREA
AIRPORTS...BUT A PASSING -SHRA/-TSRA MAY IMPACT KRIL...KASE...
KHDN...KHDN...KSBS...KEGE. OVER THE SOUTH...A FEW -SHRA/-TSRA MAY
DEVELOP OVER THE HIGHER TERRAIN DURING THE AFTERNOON. CONDITIONS
WILL IMPROVE THIS EVENING. THEN SHOWERS AND THUNDERSTORMS WILL
AGAIN INCREASE FROM THE NORTHWEST AFTER 12Z WEDNESDAY AS THE NEXT
AND STRONGER COLD FRONT MOVES INTO THE AREA.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...NONE.
UT...NONE.
&&

$$

UPDATE...EH
SHORT TERM...PF/JOE
LONG TERM...JOE/PF
AVIATION...EH



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