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000
FXUS65 KGJT 011651
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
951 AM MST SUN DEC 1 2013

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 316 AM MST SUN DEC 1 2013

THESE ARE THE PERIODS BEFORE THE STORM BUT WITH A VARIETY OF
WEATHER TO KEEP THE FORECAST COMPLICATED. WIDESPREAD STRATUS AND
PATCHY VALLEY FOG CONTINUES THIS MORNING OVER ALL BUT THE EASTERN-
MOST VALLEYS. NORTH...A PASSING WEAK WAVE OVERNIGHT HAS HAD NO
EFFECT ON THE LOW CLOUD CEILINGS OVER THE NORTHERN VALLEYS BUT
EXPECT SOME EROSION MAINLY IN NW CO AS NW GRADIENT WINDS INCREASE
AT MTN TOP LEVEL. SOUTH...CIRRUS ALONG THE AZ-NM BORDER HAS NOT
DISRUPTED VALLEY FOG THERE. DENSE FOG IS EXPECTED TO REMAIN
LOCALIZED. SOME EROSION OF THE VALLEY FOG FROM EAST TO WEST
EXPECTED THROUGH THE AFTERNOON. BUT EASTERN UTAH AND FAR WESTERN
CO VALLEYS WILL GET NO RELIEF. AFTERNOON HIGH TEMPS KEPT WELL
BELOW GUIDANCE IN THESE AREAS. MOST OF THE VALLEY LOW CLOUDS AND
FOG ARE EXPECTED TO ERODE MONDAY AFTERNOON AS WINDS ALOFT CONTINUE
TO STRENGTHEN.

LIGHT SNOW REMAINS POSSIBLE ACROSS THE NORTHERN-MOST MTNS TODAY
THROUGH MONDAY. AUTOMATED TOWERS RECORDED NO ACCUMULATION TONIGHT
WITH THE PASSING WAVE. WEAK WARM ADVECTION WILL LIMIT SNOWFALL
TODAY...BUT OROGRAPHIC SNOW REMAINS POSSIBLE MAINLY IN THE
ELKHEADS AND ZIRKELS.

ABOVE THE VALLEY INVERSIONS...NW WINDS ALOFT INCREASE TODAY AND
REMAIN WINDY THROUGH MONDAY. THE 700-600MB LAYER INCREASES TO
40KTS NORTH...30KTS SOUTH THIS AFTERNOON THROUGH MONDAY.

.LONG TERM...(MONDAY NIGHT THROUGH SATURDAY)
ISSUED AT 316 AM MST SUN DEC 1 2013

FORECAST THINKING REMAINS THE SAME THOUGH MODEL INCONSISTENCIES
CONTINUE...SOMEWHAT. MONDAY NIGHT...SOME LIGHT SNOWSHOWERS ARE
POSSIBLE OVER THE ELKHEADS AND PARK RANGES BUT WITH WINDS BECOMING
MORE WESTERLY...FAVORABLE OROGRAPHICS WILL WANE. AS THIS
OCCURS...THE LOW PRESSURE RESPONSIBLE FOR THE COMING DRASTIC
CHANGE IN WEATHER WILL BE OVER MONTANA...ROUGHLY...DEPENDING ON
WHICH MODELS ARE TO BE BELIEVED WHILE THE ASSOD SFC COLD FRONT
WILL BE TO OUR NW IN SRN ID/NRN UT. THE PRESSURE GRADIENT WILL
HAVE TIGHTENED CONSIDERABLY BY THIS TIME SO EXPECT WINDS TO BE ON
THE INCREASE. PREVIOUS MODEL RUNS PUT THE FRONT MOVING THROUGH THE
AREA TUESDAY NIGHT INTO WEDNESDAY MORNING SO OF COURSE NOW THE
MODELS HAVE SPED UP SOME WITH FRONT STARTING TO MOVE THROUGH
TUESDAY MORNING AND DROPPING SOUTH THROUGH THE DAY.
OBVIOUSLY...MODELS CONTINUE TO HAVE SOME TROUBLES WITH THIS
SYSTEM.

INTERESTINGLY...THE LATEST EC AND GFS RUNS ARE IN BETTER AGREEMENT
AND IF THEIR SOLNS COMES TO PASS...A WIDESPREAD SNOW EVENT WILL BE
THE OUTCOME. BOTH MODELS NOW SHOW THE AREA OF LOW PRESSURE QUICKLY
MOVING TO THE NE TUESDAY AFTERNOON AND EVENING WHILE A STRONG
UPPER LEVEL JET CARVES OUT A DEEP TROUGH OVER THE INTERMOUNTAIN
WEST. BOTH THE GFS AND EC NOW INDICATE THE FRONT STALLING OUT OVER
UT AND CO WHILE THE JET STREAM REMAINS OVERHEAD PROVIDING PLENTY
OF LIFT. IN FACT...DURING THE DAY WEDNESDAY THE JET IS FORECAST TO
STRENGTHEN WHICH WILL ONLY INCREASE THE AMOUNT OF LARGE SCALE LIFT
BRINGING MORE PRECIP TO THE FORECAST AREA. RIGHT NOW...LATEST
MODELS SHOWING HEAVIER PRECIP STARTING TUESDAY EVENING AND
CONTINUING THROUGH WEDNESDAY NIGHT. SOME RAIN IS POSSIBLE AT THE
START OF THIS EVENT BUT MUCH COLDER TEMPERATURES WILL ACCOMPANY
THE FRONT ALLOWING SNOW TO PREVAIL. HOPEFULLY MODELS WILL CONTINUE
TO REMAIN IN AGREEMENT SO WE CAN FINALLY NAIL DOWN THE SPECIFICS
INCLUDING SNOW AMOUNTS AND FROPA. TOYED WITH IDEA FOR SOME WINTER
STORM WATCHES BUT WILL HOLD OFF TO SEE IF THIS MODEL TREND
CONTINUES.

MOST PRECIP WILL END BY THURSDAY EVENING THROUGH SOME MTN SHOWERS
WILL PROBABLY CONTINUE. THE BIG STORY NOW BECOMES THE ARCTIC AIR
THAT WILL START SPREADING ACROSS THE AREA. BY THURSDAY...TEMPS
WILL BE RUNNING ANYWHERE FROM 15 TO 20 DEGREES BELOW NORMAL WITH
OVERNIGHT LOWS REACHING SUB-ZERO VALUES FOR NORTHERN VALLEYS AND
SINGLE DIGITS FOR THE CENTRAL AND SRN VALLEYS. THE COLD TEMPS WILL
PERSIST THROUGH SATURDAY AND IF THERE IS SNOW ON THE
GROUND...EXPECT PLENTY OF AREAS TO SEE FOG AND LOW STRATUS KEEPING
DAYTIME HIGHS EVEN COLDER.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 951 AM MST SUN DEC 1 2013

CURRENT STAGNANT PATTERN HAS ALLOWED LOW STRATUS AND PATCHY FOG
TO CONTINUE WEST OF OF A KDWX-KCAG-KGWS-KMTJ-KAIB-KDRO LINE THIS
MORNING. LIKE YESTERDAY...EXPECT THERE WILL BE SOME EROSION DUE TO
CONVECTIVE CURRENTS ALONG THE EDGES OF THE STRATUS FIELD DURING
THE AFTERNOON. HOWEVER...THE STAGNANT...INVERTED AIRMASS IS
UNLIKELY TO BE ALTERED THIS AFTERNOON AND TONIGHT DESPITE
INCREASED WESTERLY FLOW ALOFT. THEREFORE...STRATUS AND LIGHT FOG
WILL CONTINUE THROUGH THE DAY FOLLOWED BY AN EXPANSION EASTWARD
TONIGHT. FALLING TEMPERATURES WILL CAUSE FOG TO SPREAD AND BECOME
MORE DENSE OVERNIGHT AND INTO MONDAY MORNING. THE HIGHER VALLEYS
MAY EXPERIENCE LOCALIZED IFR CIGS AND VSBY THROUGH 16Z MONDAY
BEFORE GIVING WAY TO MVFR CIGS. MEANWHILE...THE LOWER VALLEYS
WILL CONTINUE TO EXPERIENCE MVFR CIGS THROUGHOUT THE DAY AND INTO
SUNDAY MORNING. AREAS EAST OF THE LINE DESCRIBED ABOVE WILL HAVE
VFR CONDITIONS THROUGHOUT THE NEXT 24 HOURS. THE ONLY EXCEPTION
BEING THE NORTHERN COLORADO MOUNTAINS WHERE LIGHT SNOW WILL BRING
SCATTERED TO NUMEROUS SNOW SHOWERS RESULTING IN MOUNTAIN OBSCURATION
OF THE ELKHEAD AND PARK RANGES.

A STRONG SYSTEM APPROACHING FROM THE NORTH WILL BEGIN TO INCREASE
THE PRESSURE GRADIENT ACROSS NORTHWEST COLORADO AND AS A RESULT...
LOW CLOUDS SHOULD BEGIN TO DISSIPATE BEFORE NOON. HOWEVER...THE
STRONGLY INVERTED EASTERN UINTA VALLEY WILL LIKELY REMAIN
UNCHANGED UNTIL THE FRONT SWEEPS THROUGH LATE MONDAY NIGHT OR
EARLY TUESDAY.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...NONE.

UT...NONE.

&&

$$

SHORT TERM...JOE
LONG TERM...TGR
AVIATION...NL