482 
FXUS65 KGJT 192113
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
313 PM MDT TUE MAR 19 2013

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT)
ISSUED AT 311 PM MDT TUE MAR 19 2013

A TRANSITORY DRY RIDGE WILL MOVE OVER THE AREA TONIGHT. THEN AN
INITIAL SHORTWAVE TROUGH WILL EJECT OUT OF A PACIFIC STORM AND
BRING CLOUDS INTO THE AREA STARTING WED MORNING. THERE APPEARS TO
BE VERY LITTLE DYNAMICS ASSOCIATED WITH THIS INITIAL WAVE...UNTIL
AFTER 18Z. WITH LITTLE QG FORCING AND SMALL UPWARD MOTION SHOWN ON
TIME/HTS OVER THE SAN JUAN MTS...WILL EXPECT MAINLY ORGPHC SHOWERS
IN THE LATE AFTERNOON...THEN INCREASING AT NIGHT AS THE MOISTURE
LOWERS AND FAIR UPWARD MOTION ARRIVES AFTER 06Z THU MORNING...WITH
A BRIEF PEAK OF UPWARD OMEGA AT 12Z. THE TROUGH PASSAGE IS
EXPECTED AROUND 06Z THU WITH A FEW DEGREES OF COLD ADVECTION
FOLLOWING THAT. WILL STAY WITH THE SPS CURRENTLY OUT AND NOT ISSUE
AN ADVISORY OVER THE MOUNTAINS AT THIS TIME...AS THERE IS ENOUGH
UNCERTAINTY REMAINING ABOUT RECEIVING MORE THAN JUST LOCAL
ADVISORY CRITERIA SNOWFALL.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 311 PM MDT TUE MAR 19 2013

COLD UPPER TROUGH PUSHES A COLD FRONT SOUTHEAST ACROSS THE FORECAST 
AREA ON THURSDAY...THOUGH THE FRONT WEAKENS AS IT MOVES SOUTH OF 
GRAND MESA. BEST Q-G FORCING REMAINS TO OUR NORTH AND EAST AS THE 
UPPER TROUGH CROSSES THURSDAY AFTERNOON. BEST SNOW ACCUMS LOOK TO BE 
IN THE CENTRAL AND NRN CO MTNS THU AND GENERALLY ABOVE 9000 FT. ANY 
PRECIPITATION IN VALLEYS SHOULD BE RAIN FROM THE I-70 CORRIDOR 
SOUTH...WITH RAIN AND/OR SNOW ACROSS THE NORTH.

MODELS CONTINUE THE RECENT TREND OF DEVELOPING A LARGE UPPER TROUGH 
OVER MONTANA/ALBERTA/SASK LATE IN THE WEEK. GFS/ECMWF BOTH SHOW BACKSIDE 
JET ENERGY NOW DIGGING A TROUGH OVER UT/CO AND EVENTUALLY CLOSING 
OFF A 500 MB LOW OVER ERN UT/WRN CO BY SAT MORNING. NOT A LOT OF 
MOISTURE ASSOCIATED WITH IT...700 MB SPECIFIC HUMIDITIES UNDER 2 
G/KG...BUT STILL LIKELY TO SEE SOME SNOW IN THE NRN AND CENTRAL MTNS 
FRI NIGHT AND SAT MORNING AS THE UPWARD Q-G FORCING BULLSEYE AND 
COLD POOL ALOFT CROSSES NW CO. THE PATTERN REMAINS PROGRESSIVE WITH 
THE UPPER LOW SLIDING INTO KS/OK BY SAT NIGHT...BUT UNSETTLED NW 
FLOW WILL KEEP CLOUDS AND SOME CHANCE OF MTN PRECIP MAINLY ACROSS 
THE NORTH HALF OF THE FORECAST AREA THROUGH MONDAY. BOTH ECMWF AND 
GFS NOW SHOW A PACIFIC RIDGE INCHING INLAND TO THE GREAT BASIN 
TUESDAY.

THE SHIFT TO MORE TROUGHING OVER UT/CO PORTENDS COOLER THAN NORMAL 
TEMPS FOR THE FORECAST AREA THROUGH THE WEEKEND.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY AFTERNOON)
ISSUED AT 311 PM MDT TUE MAR 19 2013

FLIGHT CONDITIONS SHOULD REMAIN VFR AT ALL TAF SITES THROUGH
TONIGHT AND HIGH PRESSURE TRAVELS OVER THE AREA. 

THE NEXT CHANGE IS EXPECTED WEDNESDAY WHEN AN APPROACHING TROUGH
WILL SPREAD LOWERING CLOUDS ACROSS THE AREA. BEGINNING AFTER
SUNRISE WED...LAYERED MID LEVEL CLOUDS WILL SPREAD FROM WEST TO
EAST WITH A LOWERING CLOUD DECK THROUGHOUT THE DAY. BY 21Z WED
MOST MOUNTAIN TOPS WILL BE OBSCD...AND RAIN AND SHOW SHOWERS WILL
BE DEVELOPING OVER THE SAN JUAN...LA SAL AND ABAJO MTS AS WELL AS
PORTIONS OF THE CENTRAL AND NORTHERN CO AND ERN UT MTS.

&&

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

$$

SHORT TERM...CC
LONG TERM...JAD
AVIATION...CC