501 
FXUS65 KGJT 190952
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
352 AM MDT TUE MAR 19 2013

.SHORT TERM...(TODAY THROUGH WEDNESDAY)
ISSUED AT 352 AM MDT TUE MAR 19 2013

MOUNTAIN WINDS HAVE DROPPED OFF IN THE LAST FEW HOURS...WITH THE
STRONGEST WINDS EAST OF THE CONTINENTAL DIVIDE EARLY THIS MORNING.
EXPECT THE GRADIENT TO CONTINUE TO WEAKEN TODAY...BRINGING A
RETURN TO THE TYPICAL DIURNAL UPSLOPE/DOWNSLOPE WINDS TO MOST
LOCATIONS.

AN UPPER RIDGE WILL MOVE FROM ALONG THE COAST THIS MORNING TO OVER
THE GREAT BASIN INTO BRITISH COLUMBIA THIS AFTERNOON. BY EARLY
WEDNESDAY THE RIDGE AXIS IS PROGGED TO BE OVERHEAD...IN A SOMEWHAT
FLATTENED FASHION ACROSS ITS SOUTHERN TIER.

A WEAK EMBEDDED WAVE WILL UNDERCUT THE RIDGE AND PASS OVER
NORTHERN NEW MEXICO TODAY. SATELLITE IMAGES...AND MODELS INDICATE
A GOOD SURGE OF MAINLY MID TO HIGH LEVEL MOISTURE WILL INVADE FROM
THE WEST. EXPECT THAT THIS MOISTURE WILL BE DEEP ENOUGH FOR A FEW
SHOWERS OVER THE SAN JUANS. OTHERWISE MOSTLY CLOUDY SKIES WILL
PREVAIL. TEMPERATURES WILL GENERALLY BE SIMILAR TO A COUPLE
DEGREES WARMER THAN MONDAY'S.

PERIODS OF CLOUDS WILL CONTINUE TO STREAM OVER THE AREA TONIGHT IN
THE MOIST PACIFIC FLOW. THIS WILL KEEP CONDITIONS ON THE MILD
SIDE.

ON WED...THE AIR MASS WILL CONTINUE TO MOISTEN AS THE RIDGE SHIFTS
EAST AND AN UPPER LEVEL TROUGH APPROACHES FROM THE NORTHWEST.
ISENTROPIC UPGLIDE AND DEEP MOISTURE BY THE AFTERNOON WILL ALLOW
SHOWERS TO BEGIN ACROSS THE AREA. HOWEVER THE BETTER ACTIVITY WILL
WAIT UNTIL AFTER THE SHORT TERM PERIOD. IN SPITE OF THE INCREASED
CHANCE OF SHOWERS...HIGH TEMPERATURES SHOULD WARM A COUPLE DEGREES
IN THE WARM ADVECTION PATTERN.

.LONG TERM...(WEDNESDAY NIGHT THROUGH MONDAY)
ISSUED AT 352 AM MDT TUE MAR 19 2013

PACIFIC ENERGY SPREADS ACROSS THE CENTRAL ROCKIES ON WEDNESDAY NIGHT 
WITH THE TROUGH PASSAGE ON THURSDAY AFTERNOON.  THIS SYSTEM WILL BE 
WEAKENING AS IT MOVES DOWNSTREAM FROM THE LONG WAVE TROUGH 
POSITION...BUT NEVERTHELESS THERE IS FAIR AMOUNT OF PACIFIC MOISTURE 
THAT MOVES ACROSS THE CENTRAL ROCKIES FOR DECENT SNOWFALL.  
HIGH CONFIDENCE THAT ADVISORY LEVEL SNOW AMOUNTS WILL BE REACHED
AND WILL ADDRESS THIS WITH A SPECIAL WEATHER STATEMENT.
PROGRESSIVE SHORT WAVE WILL BE TOO FAST FOR HEAVIER SNOW AMOUNTS
AS IT MOVES DOWNSTREAM BY THURSDAY EVENING. SNOW LEVELS WILL BE
ABOVE MOST VALLEY FLOORS AND RANGE FROM 7000 FEET NORTH TO ABOVE
8000 FEET SOUTH...BUT LOWER ON THURSDAY WITH APPROACHING TROUGH
AXIS. BY THE TIME THE SNOW LEVELS DROP BELOW 7000 FEET...MOST OF
THE MOISTURE AND SHORT WAVE ENERGY WILL BE GONE.

BUILDING RIDGE OVER THE EASTERN PACIFIC ALLOWS FOR A DEEP COLD 
TROUGH TO GET CARVED OUT OVER UTAH AND COLORADO.  FAIR AGREEMENT 
BETWEEN THE GFS AND ECMWF THAT THE TROUGH WILL EVOLVE INTO A CLOSED 
LOW CIRCULATION SOMEWHERE OVER UTAH.  MODELS HAVE BEEN LACKING RUN 
TO RUN CONTINUITY...SO NOT COMPLETELY READY TO BUY THIS SOLUTION.
THE STRENGTH OF THE THERMAL BOUNDARY AND CYCLOGENETICALLY FORCING
INDICATE THAT THE POTENTIAL EXISTS FOR COLDER WINTRY WEATHER ON
SATURDAY. EXCEPT THIS SYSTEM WILL BE MOISTURE STARVED GIVEN ITS
CONTINENTAL AIR MASS CHARACTERISTICS. THE BEST THREAT FOR SNOW
WILL BE ACROSS NORTHWEST COLORADO WITH SNOW AMOUNTS DEPENDENT ON
THE AMOUNT OF WRAPAROUND MOISTURE. TOO MANY QUESTION MARKS AT THIS
POINT AND WILL KEEP POP VALUES IN THE CHANCE RANGE (30%-50%) FOR
THE NWRN COLORADO MOUNTAINS.

SUNDAY AND MONDAY...COLD DEEP TROUGH PROBABLY MOVES INTO THE MIDWEST
AND KEEPS NORTHWEST FLOW ACROSS THE REGION. ADDITIONAL SHORT WAVE
ENERGY MAY AFFECT THE NRN DIVIDE...BUT THE MODEL SPREAD BECOMES
MORE PRONOUNCED FOR LOWER CONFIDENCE IN ANY MODEL GUIDANCE.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 352 AM MDT TUE MAR 19 2013

A WEAK DISTURBANCE AND A SURGE OF MOISTURE WILL BRING A FEW SNOW
SHOWERS TO THE SAN JUAN MOUNTAINS TODAY. THIS WILL RESULT IN BRIEF
OBSCURATIONS OF THE HIGHER PEAKS THROUGH 03Z WEDNESDAY.
ELSEWHERE...VFR CONDITIONS WILL CONTINUE FOR ALL AIRPORTS IN
EASTERN UTAH AND WESTERN COLORADO. BY SUNRISE WEDNESDAY...A FEW
MOUNTAIN SNOW SHOWERS MAY DEVELOP AHEAD OF THE NEXT SYSTEM
APPROACHING FROM THE NORTHWEST.

&&

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

$$

SHORT TERM...EH
LONG TERM...PF
AVIATION...EH