Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 101320
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
720 AM MDT WED SEP 10 2014

.UPDATE...
ISSUED AT 715 AM MDT WED SEP 10 2014

PLENTY OF DENSE FOG ALONG I-70 FROM FRUITA THIS MORNING AND ALSO
IN GRAND JUNCTION. WHILE THE LAYER IS PRETTY SHALLOW...VISIBILITIES
ARE AT OR LESS THAN A 1/4 MILE FOR MUCH OF THE GRAND VALLEY. WENT
WITH A DENSE FOG ADVISORY THROUGH 10AM TO ACCOUNT FOR THIS. ONCE
THE FOG BURNS OFF...EXPECT A DRY DAY WITH PLENTY OF SUN AND
SEASONAL TEMPS.

&&

.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 409 AM MDT WED SEP 10 2014

SHORT WAVE CROSSES THE DIVIDE BEFORE DAYBREAK WITH SOME CONTINUING
SHOWERS OVER THE CENTRAL MOUNTAINS. MOST OF THE SHOWERS WILL HAVE
ENDED BY SUNRISE. RELATIVE HUMIDITY IS NEAR 100 PERCENT AT MANY
SPOTS WITH SOME VALLEY STRATUS. BELIEVE THERE IS ENOUGH MIXING
THAT STRATUS WILL NOT BECOME WIDESPREAD.

MUCH DRIER AIR MASS AS PRECIPITABLE WATER TREND SHARPLY LOWER AS
THE DAY PROGRESSES. HOWEVER IN THE WAKE OF THE TROUGH...SHALLOW
POTENTIAL INSTABILITY REMAINS. ADD MORE SUNSHINE TODAY WILL
RESULT IN SOME LOW CLOUD TOP POPCORN LIKE SHOWERS THAT HUG THE
WRN COLORADO HIGH TERRAIN. THESE SHOWERS WILL STRUGGLE TO SUSTAIN
THEMSELVES GIVEN THE LOWERING PWAT VALUES...SO MINIMAL AREAL
COVERAGE AND ANY OROGRAPHIC SHOWERS WILL BE SHORT LIVED.

TONIGHT AND THURSDAY...STRONG LOW PRESSURE OVER HUDSON BAY AND A
RIDGE AMPLIFYING ACROSS NORTHWEST CANADA WILL FORCE ANOTHER TROUGH
ACROSS THE ROCKIES AND PLAINS TO OUR NORTH THIS PERIOD. UPPER LEVEL
ASCENT WILL BRUSH OUR NORTHERN CWA ON THURSDAY AS THE JET ROUNDS THE
BASE OF TROUGH THEN REFORMS ON THE DOWNSTREAM SIDE. THE SOURCE
REGION OF THIS TROUGH IS INTERIOR CANADA AND THE AIRMASS SLIDING
SOUTHWARD IN THE WAKE OF THE JET MAX PASSAGE WILL BE FAIRLY COOL.
THE BULK OF THE MOISTURE IS ALSO SHALLOW AND WILL NOT BE MAKING THE
TRIP OVER THE HIGHER TERRAIN...INSTEAD SLIDE DOWN THE HIGH PLAINS.
THEREFORE A DRY FORECAST REMAINS IN PLACE ACROSS OUR CWA. MODELS ARE
IN GOOD AGREEMENT IN PUSHING A DRY COLD FRONT ACROSS OUR NORTHERN
BORDER THURSDAY AFTERNOON...LATE ENOUGH THAT HIGH TEMPERATURES
SHOULD NOT BE AFFECTED. GOOD MIXING IN THE PREFRONTAL ENVIRONMENT
WILL LEAD TO A DECENT WARMUP THURSDAY AND DID TREND HIGHS UPWARD A
BIT.

.LONG TERM...(THURSDAY NIGHT THROUGH TUESDAY)
ISSUED AT 409 AM MDT WED SEP 10 2014

THURSDAY NIGHT INTO FRIDAY...THE FRONT SHOULD MAKE SOUTHERN
PROGRESS ACROSS AND OUT OF OUR CWA THURSDAY NIGHT...WEAKENING AS
IT DOES SO. COOLER AIR FILTERING IN BEHIND THE FRONT WILL LEAD TO
LOWS QUITE A BIT CHILLIER THAN WEEKS PAST. GUIDANCE IS SUGGESTING
THAT NEAR FREEZING TEMPERATURES WILL BE POSSIBLE ALONG THE YAMPA
RIVER BASIN BY MORNING AND COULD LEAD TO SOME PATCHY FROST AS
SKIES APPEAR MAINLY CLEAR. AT THIS TIME A SEASON ENDING FREEZE UP
NORTH APPEARS UNLIKELY. THE NORTHERN HALF OF THE CWA SHOULD SEE
HIGHS IN FRIDAY DIP BY ABOUT 5 DEGREES BEHIND THE FRONT...BUT NOT
AS NOTICEABLE DOWN SOUTH AS THE AIRMASS MODIFIES.

WEST NORTHWEST FLOW LASTS THROUGH SATURDAY...BUT THE SUNDAY AND
MONDAY TIME PERIOD WILL BE MARKED BY AN AMPLIFYING RIDGE OVER THE
WEST COAST STATES. BY TUESDAY THE STRONG RIDGE WILL BE POSITIONED
OVER THE ROCKY MOUNTAIN STATES. WITH AMPLE SUNSHINE AND RISING
HEIGHT LEVELS...EXPECT A WARMING TREND THAT SEND TEMPS TO ABOVE
CLIMOTOLOGY EARLY NEXT WEEK. THE MONSOON SEASON IS COMING TO AN
END AND MOST LIKELY WILL NOT BE A FACTOR THROUGH THE EXTENDED
PERIOD. HOWEVER STEEP AFTERNOON LAPSE RATES AND CONVECTIVE
POTENTIAL DO SUPPORT A CHANCE OF AFTERNOON THUNDERSTORMS OVER THE
SAN JUAN MOUNTAINS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 458 AM MDT WED SEP 10 2014

SCT -SHRA OVER THE WEST CENTRAL MOUNTAINS NEAR THE DIVIDE WILL BE
ENDING AROUND 15Z THIS MORNING. HOWEVER ISOLD -SHRA MAY STILL
OCCUR THROUGH THE AFTERNOON OVER THE HIGH COUNTRY.

SOME STRATUS HAS FORMED EARLY THIS MORNING FOR LOCALIZED CIGS AOB
BKN010. STRATUS IS NOT WIDESPREAD AND WILL DISSIPATE BY 15Z THIS
MORNING. AFTER 15Z...VFR WILL BE PREVAILING FOR THE ENTIRE REGION.

NO AVIATION HAZARDS ARE EXPECTED TONIGHT WITH SKC CONDITIONS.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...DENSE FOG ADVISORY UNTIL 10 AM MDT THIS MORNING FOR COZ006.

UT...NONE.
&&

$$

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



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