FXUS65 KGJT 021035
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
334 AM MST WED DEC 2 2009

.SHORT TERM...TODAY THROUGH THURSDAY NIGHT...

SATELLITE WATER VAPOR LOOP SHOWING SHORTWAVE ENERGY DIGGING A
POSTIVELY TILTED UPPER TROUGH DOWN THE NRN ROCKIES EARLY THIS
MORNING. THIS TROUGH EXPECTED TO SLOWLY DROP ACROSS OUR AREA TODAY
THROUGH THU. WHILE THIS TROUGH CARRIES A MEAGER SUPPLY OF MOISTURE
AND NOT MUCH SNOW IS EXPECTED...IT WILL BRING A BIG CHANGE TO COLDER
TEMPERATURES. HIGH TEMPS TODAY EXPECTED TO BE 10-20 DEGS F. COLDER
THAN YESTERDAY ACROSS THE CENTRAL AND NORTHERN PORTIONS OF OUR
FORECAST AREA.

SNOW WAS OBSERVED ACROSS PORTIONS OF SRN WY AND IN THE PARK RANGE
AROUND STEAMBOAT SPGS PRIOR TO 10Z.  WFO RIVERTON ESTIMATED ABOUT AN
INCH OF NEW SNOW AT ROCK SPGS AND GREEN RIVER...AND A LITTLE MORE
AROUND RAWLINS. MT WERNER AUTOMATED STATION ABOVE STEAMBOAT SPGS
REPORTED SNOW AS WELL...BUT NEARBY TOWER SNOTEL NOT INDICATING MUCH
ACCUMS. LOW CLOUDS SEEN ON SATELLITE MAY BE PRODUCING SOME
LIGHT SNOW ON THE NRN SLOPES OF THE UINTA MTNS IN NE UT AS WELL.

THIS SNOW LIKELY ASSOCIATED WITH THE NOSE OF THE UPPER JET AND THE
700 MB FRONT/BAROCLINIC ZONE...WHICH WILL SHIFT INTO NW CO THIS
MORNING. THE CYCLONICALLY CURVED JET AND THE H7 BAROCLINIC ZONE MAKE
THEIR WAY SOUTH TO WEST-CENTRAL CO BY ABOUT MIDDAY AND INTO SW CO
THIS AFTERNOON. MODELS SHOW MOISTURE DECREASING THROUGH THE DAY...SO
WILL HAVE THE HIGHEST POPS IN THE N AND CENTRAL CO MTNS. A COUPLE
INCHES OF SNOW ACCUMS MAINLY NEAR THE DIVIDE IS ALL THAT IS EXPECTED.
TROUGH AXIS DOESN/T CLEAR THE SRN PORTION OF THE FORECAST AREA UNTIL
LATE THU...AS ANOTHER PUSH OF ENERGY AND COLD AIR ARRIVE ON THU.
BUT WITH MOISTURE LACKING...WILL KEEP THE MENTION OF SNOW RESTRICTED
TO NEAR THE DIVIDE IN GENERAL TONIGHT THROUGH THU.

MAIN STORY IS THE CHANGE TO COLDER TEMPS. COLDER AIR SPREADS SOUTH
ACROSS THE AREA TODAY...AND CONTINUES THROUGH THU. TEMPS MAY NOT RISE
MUCH THIS AFTERNOON ACROSS THE NORTH AS A RESULT OF THIS INTRUSION.
LOWS TONIGHT IN THE SINGLE DIGITS TO LOW TEENS WILL BE COMMON...WITH
SUB-ZERO TEMPS IN SOME NRN VALLEYS AND MTNS. CONTINUED COLD THU AND
THU NIGHT. EXPECT STRONG VALLEY INVERSIONS AT NIGHT.

.LONG TERM...FRIDAY THROUGH TUESDAY...

INCREASINGLY COMPLICATED FORECAST SETTING UP AS WE MOVE THROUGH THE
EXTENDED PERIOD. DRY NW FLOW STARTS OFF FRIDAY AND FRIDAY NIGHT
WITH BRIEF SHRTWV RIDGING RIDING THROUGH. FLOW ALOFT COMES BACK
AROUND TO THE WEST AND EVENTUALLY SOUTHWEST BY THE END OF THE
WEEKEND AS LOW PRESSURE DROPS SOUTH OUT OF CANADA AND INTO THE
PACNW.  FAVORABLE WESTERLY FLOW SATURDAY AFTERNOON THROUGH SUNDAY
AND INCREASE IN MID LEVEL MOISTURE WILL BRING A CHANCE FOR SNOW
OVER MANY OF OUR MOUNTAIN AREAS...ESPECIALLY ON SUNDAY AS
DIFLUENT FLOW BREAKS OUT AHEAD OF AN APPROACHING SHRTWV TROUGH.
VERY MOIST SOUTHWEST FLOW WILL THEN SET UP OVER THE REGION BY
MONDAY AND CONTINUE THROUGH TUESDAY AS THE UPPER LOW OVER THE
PACIFIC NORTHWEST RETROGRADES TO THE SOUTHWEST...BEFORE FINALLY
KICKING OUT LATE MONDAY. WITH COPIOUS AMOUNTS OF MOISTURE PROGGED
TO MOVE INTO THE REGION...AND WITH COLD AIR ALREADY IN PLACE...
CONDITIONS WILL BE MORE FAVORABLE FOR A SIGNIFICANT PRECIPITATION
EVENT OVER OUR FORECAST AREA. WILL BE KEEPING A CLOSE EYE ON THIS
OVER THE NEXT FEW DAYS...WITH HIGHLIGHTS A DEFINITE POSSIBILITY AS
WE MOVE CLOSER TO THE EVENT. THE GFS IS INDICATING A SWEEPER TROUGH
MOVING THROUGH ON TUESDAY...WHICH WILL BRING AN END TO THE PRECIP
EVENT FROM WEST TO EAST. HOWEVER...THE ECMWF IS LESS AGGRESSIVE WITH
THIS FEATURE...INDICATING THE MOISTURE TAP WILL CONTINUE THROUGH
MUCH OF THE WEEK. AS A RESULT...WILL BACK OFF THE HIGHER POPS FOR
TUESDAY NIGHT AND WEDNESDAY.  TEMPS WILL REMAIN ON THE COLD SIDE OF
NORMAL FOR MUCH OF THE EXTENDED PERIOD...ALTHOUGH SOME MODERATION
WILL OCCUR AS THE DEEPER PACIFIC MOISTURE ARRIVES WITH WEAK WAA
ALOFT.

&&

.AVIATION...

A STRONG COLD FRONT WILL EXIT THE SOUTHERN PORTIONS OF THE
FORECAST AREA BY 15Z THIS MORNING. BEHIND THE FRONT...LOCAL AREAS
OF MVFR TO IFR CIGS AND VSBYS WILL OCCUR GENERALLY EAST OF A LINE
FROM KHDN TO KASE AS AREAS OF LIGHT SNOW LINGER NEAR THE
CONTINENTAL DIVIDE THROUGH LATE THIS AFTERNOON. OTHERWISE...VFR
CONDITIONS WILL PREVAIL OVER THE REGION.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...JAD
LONG TERM....JDC
AVIATION.....JDC