FXUS65 KGJT 111213
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
513 AM MST FRI DEC 11 2009

...SNOW RETURNS THIS WEEKEND...

.SHORT TERM...TODAY THROUGH SATURDAY NIGHT...
EXPECT PATCHY FREEZING FOG TO DEVELOP AGAIN TODAY ESPECIALLY NEAR
RIVERS AND STREAMS. GRADIENT RELAXES A BIT AS THE BROAD NORTHERN
TROUGH SHIFTS EAST AND NORTH. WINDS ALOFT BECOME ZONAL. COLD AIR WILL
CONTINUE TO BE TRAPPED IN VALLEY LOCATIONS. TEMPERATURES WILL WARM
SLIGHTLY TODAY WITH WARM ADVECTION ALOFT OF A FEW DEGREES. DO NOT
FORESEE MUCH MIXING TO THE LOWER ELEVATIONS THEREFORE CONTINUED THE
TREND TO REMAIN BELOW GUIDANCE FOR VALLEYS.  THE FIRST IN A SERIES OF
SHORTWAVES TRACKS EAST THROUGH THE SOUTHERN PART OF THE FLOW AND OVER
EASTERN UT AND WESTERN CO LATER THIS EVENING. MOISTURE WILL INCREASE
CAUSING AN INCREASE IN HIGH CLOUDS DURING THE DAY. THE ATOMS BECOMES
SATURATED THROUGH 500 MB LATER THIS EVENING. BEST CHANCE FOR
PRECIPITATION IS LATE NIGHT INTO EARLY MORNING WITH ISENTROPIC LIFT.
SNOW WILL FAVOR THE WEST SLOPES. THE SHORTWAVE EXITS EARLY
SATURDAY. PRECIP CHANCES WILL DECREASE ALTHOUGH WITH THE MOISTURE
SATURATION FROM LOWER TO NEAR MID LEVELS KEEPS SHOWERS LINGERING. THE
NEXT SHORTWAVE ENTERS THE REGION SATURDAY AFTERNOON AND EXITS EARLY
EVENING...ALTHOUGH THERE IS STILL UNCERTAINTY IN THE TIMING. SHOW
SHOWERS WILL INCREASE DURING THE AFTERNOON ALTHOUGH ACCUMULATIONS
SHOULD BE LIGHT. MOISTURE WILL AGAIN DEEPEN SATURDAY NIGHT AS THE
FIRST PORTION OF THE MAIN SYSTEM ENTERS THE REGION. SNOW WILL BEGIN
AND INCREASE IN COVERAGE AND INTENSITY LATE SATURDAY NIGHT AND
CONTINUE INTO SUNDAY.

.LONG TERM...SUNDAY THROUGH THURSDAY...
MODELS WERE IN GOOD AGREEMENT WITH THIS WEEKEND'S STORM. ALL
INDICATED THE BEST MOISTURE AND DYNAMIC FORCING WILL SWEEP OVER THE
AREA ON SUNDAY. MOIST 7-5H LAYER WITH A SPECIFIC HUMIDITY ON THE
ORDER OF 4 G/KG WILL BE OVERRIDING COLD AIR WHICH BECAME ENTRENCHED
OVER THE REGION FOLLOWING THE STORM EARLIER THIS WEEK RESULTING IN
WIDESPREAD SNOWFALL. PVA ASSOCIATED WITH APPROACHING TROF COMBINED
WITH DIVERGENCE AT JET LEVEL SHOULD ENHANCE SNOWFALL. AT THIS POINT
...EXPECT SNOW AMOUNTS FOR SATURDAY NIGHT AND SUNDAY TO FALL BELOW A
FOOT ON AVERAGE SO WILL NOT BE HOISTING A WATCH WITH THIS PACKAGE.
A BIT UNCERTAIN WHETHER THE STRONG SOUTHWEST 7H FLOW COMBINED WITH
TROF PASSAGE WILL BE SUFFICIENT TO MIX OUT VALLEY INVERSIONS ON
SUNDAY. CONSEQUENTLY...HEDGED ON HIGHS AND UNDERCUT MOS GUIDANCE BY
AROUND 5 DEGREES ACROSS THE LOWER ELEVATIONS. HOWEVER...APPEARED
LOWER VALLEYS MAY WARM SUFFICIENTLY FOR RAIN OR MIXED RAIN AND SNOW
SUNDAY AFTERNOON. LARGELY OROGRAPHIC SNOW WILL CONTINUE OVER THE
CONTINENTAL DIVIDE SUNDAY NIGHT.

MONDAY WILL SEE A DOWNTURN...BUT ENOUGH MOISTURE/INSTABILITY WILL
REMAIN IN THE LOWER LEVELS FOR A CONTINUATION OF OROGRAPHIC SNOW OVER
THE MOUNTAINS...ESPECIALLY ALONG THE DIVIDE. SOME ACTIVITY WILL
LINGER OVER THE NORTHERN MOUNTAINS THROUGH MONDAY NIGHT.

RIDGING THEN DEVELOPS OVER THE WEST THROUGH THE REMAINDER OF THE
PERIOD FOR A DRIER NORTHWEST FLOW OVER OUR FORECAST AREA. INVERSIONS
WILL AGAIN SET UP IN MOST VALLEYS WITH SNOW STILL ON THE GROUND...BUT
CONDITIONS ARE NOT EXPECTED TO BE QUITE AS COLD AS THE LAST COUPLE OF
DAYS.

&&

.AVIATION...

PATCHY FOG WILL OCCASIONAL RESTRICT CIGS AND VSBYS INTO THE MVFR/IFR
CATEGORIES...ESPECIALLY NEAR AIRPORTS BLANKETED IN SNOW COVER
THROUGH 18Z. OTHERWISE...EXPECT VFR CONDITIONS REGION-WIDE THIS
AFTERNOON AND EVENING. PATCHY FOG MAY FORM AGAIN LATER TONIGHT.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...NONE.
UT...NONE.

&&

$$

SHORT TERM...AS
LONG TERM....NL/EH
AVIATION.....TGJT