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