000 FXUS65 KRIW 162136 AFDRIW AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 236 PM MST MON FEB 16 2009 .SHORT TERM...TONIGHT THROUGH THURSDAY COMPLEX SCENARIO SETTING UP FOR THE NEXT 36 TO 48 HOURS WITH COMBINATION OF NEWD MOVING SHORTWAVE...UPPER LOW AND SWD MOVING ARCTIC CLIPPER. MODELS ARE NOT AS AGGRESSIVE EAST OF THE DIVIDE AS YESTERDAY...ESPECIALLY ON WEDNESDAY. SOME OF THAT IS DUE TO A FASTER SWD MOVEMENT WITH THE ARCTIC WAVE AND PART OF IT IS THE MODELS SHOWING A WEAKER REMNANT UPPER LOW MOVING FROM ERN IDAHO TO CENTRAL WYO. THE END RESULT FOR THE SENSIBLE WEATHER MAY NOT BE ALL THAT DIFFERENT BUT THE SNOWFALL AMOUNTS ARE STILL A CHALLENGE. IT STILL LOOKS LIKE THE SHORTWAVE THAT SHOOTS OUT THE BOTTOM OF THE OFFSHORE CA LOW WILL MOVE NE INTO SWRN WY THIS EVENING AND ACROSS ALL OF THE WEST BY AROUND MIDNIGHT. REMNANT UPPER LOW WILL TRACK FROM THE TETONS TO THE WIND RIVER BASIN TUESDAY MORNING WITH CONVERGENCE AXIS ALONG ITS TRACK AS SWD MOVING FRONT INTERACTS WITH IT TUESDAY AFTERNOON. STEEP LAPSE RATES AND LOW LIFTED INDICES MAY LEAD TO LATE AFTERNOON CONVECTION FORMING OVER THE SERN ABSAROKAS AND OWL CREEKS MOVING SE ACROSS THE WIND RIVER BASIN. THE LANDER FOOTHILLS MAY ALSO SEE SOME SNOW OR MIXED RAIN AND SNOW SHOWERS LATE IN THE DAY. STILL NOT CLEAR CUT ON THE EXACT SCENARIO BUT HAVE CONTINUED TRENDS OF HIGHER POPS IN THE AREA. OTHERWISE...SNOW WILL CONTINUE OUT WEST WITH POSSIBLE HIGHLIGHTS NEEDED ANYWHERE FROM THE TETONS SWD EARLY TUESDAY INTO EARLY WEDNESDAY. SINCE MOST OF THE SNOW WILL BE TUESDAY AND TUESDAY NIGHT...WILL LET THE NEXT CREW GIVE IT ONE MORE LOOK BEFORE ISSUING ANY POSSIBLE HIGHLIGHTS. BEST SNOW IN THE TETONS SHOULD BE FROM AROUND MIDDAY TUESDAY INTO EARLY WEDNESDAY WHEN W TO NW FLOW DEVELOPS. SWD MOVING ARCTIC WAVE WILL AFFECT THE N AND E LATE TUESDAY NIGHT INTO WEDNESDAY WITH COLDER AIR AND LIGHT SNOW. STILL SOME QUESTION ON HOW AND IF THE LEFT OVER DEFORMATION AXIS WILL INTERACT WITH THE COLD FRONT ON WEDNESDAY. MODELS HAVE BACKED AWAY FROM THIS IDEA SINCE YESTERDAY BUT I STILL THINK THERE IS SOME POTENTIAL AND THIS WILL HAVE TO BE WATCHED FOR OUR ERN ZONES. SOME LIGHT SNOW OR FLURRIES MAY LINGER IN THE WEST INTO WEDNESDAY NIGHT BEFORE ENDING OR RETREATING TO THE HIGHEST NWRN PEAKS. TEMPERATURES WILL STILL BE TRICKY AROUND THE CENTRAL ZONES AHEAD OF THE FRONT WHERE WARMER MID LEVEL TEMPS PERSIST BUT ARE BALANCED SOME BY INCREASING CLOUD COVER. BUMPED TEMPS UP A COUPLE DEGREES BASED ON HOW EASILY WE CRACKED 40 TODAY AND WARMER MID LEVEL TEMPS THAT REMAIN THROUGH MIDDAY TUESDAY. OTHERWISE...IT SHOULD BE QUITE A BIT COOLER IN THE ERN ZONES ON WEDNESDAY WITH H7 TEMPS OF -11 TO -12...CLOUDS AND PERIODS OF LIGHT SNOW...ESPECIALLY IN THE MORNING. INVERSIONS BEGIN TO RETURN ON THURSDAY WITH SW BREEZES RETURNING TO THE WIND CORRIDOR. .LONG TERM...THURSDAY NIGHT THROUGH MONDAY A WEAK SHORTWAVE IN NW FLOW APPROACHES NRN WY LATE THURSDAY AND PASSES THROUGH THURS NIGHT. WILL KEEP LOW PRECIP CHANCES IN THE MTS OF THE NORTH. NORTHERN JOHNSON COUNTY MAY SEE LIGHT DUSTING OF SNOW THURS NIGHT. FRIDAY SEEMS DRY AS UPPER RIDGE AXIS TO THE WEST AMPLIFIES. HAVE LOWERED PRECIP CHANCES IN THE MTS TO SLIGHT CHANCE AND MAY GO DRY IF MODELS CONTINUE TO SHOW LACK OF MOISTURE FRI. UPPER RIDGE OVER THE AREA FRIDAY NIGHT AND SATURDAY WITH DRY WEATHER EXPECTED. SAT NIGHT LOOKS DRY ASIDE FROM A FEW SNOW SHOWERS DEVELOPING LATE SAT NIGHT IN THE WRN MTS. THIS TIMING MAY BE TOO FAST AND WILL SEE HOW THINGS LOOK TONIGHT. GFS AND ECMWF MODELS SIMILAR WITH NEXT TROUGH NEXT SUNDAY INTO MONDAY. PRECIP CHANCES TO INCREASE IN WRN WY SUN AFTERNOON WITH BETTER CHANCE OF PRECIP SUN NIGHT THROUGH MONDAY NIGHT. WILL WATCH THIS OVER THE NEXT FEW NIGHTS AND ADJUST FORECAST AS NEEDED. AS FOR TEMPS... SEASONAL TO ABOVE NORMAL HIGHS AND LOWS THROUGH THE WEEKEND WITH SOME COOLING FOR NEXT MONDAY DUE TO PRECIP AND COLDER AIR WITH TROUGH. && .AVIATION... A WEAKENING TROUGH OF LOW PRESSURE WILL BE TRACKING EAST NORTHEAST TO THE CENTRAL ROCKIES TONIGHT. THIS WEATHER FEATURE WILL SPREAD LIGHT SNOWFALL AND LOWERING CIGS INTO FAR WESTERN WYOMING AND THE UPPER GREEN RIVER BASIN TONIGHT. EXPECT MVFR CONDITIONS TO DEVELOP IN THESE AREAS TONIGHT LOWERING TO IFR BY SUNRISE TUESDAY. MVFR CONDITIONS WILL DEVELOP OVER SWEETWATER COUNTY INCLUDING KRKS BY 09Z TONIGHT WITH CONDITIONS BECOMING IFR BY 17Z. CONDITIONS WILL IMPROVE TO MVFR OVER KPNA AND KBPI EXCEPT WILL REMAIN IFR...OCCASIONALLY LIFR OVER THE FAR WEST INCLUDING KJAC WHERE A MOIST WESTERLY UPSLOPE FLOW WILL PROLONG THE HEAVIER SNOW THERE. IN THE MEANTIME A SURFACE COLD FRONT WILL BE SHIFTING THE WINDS TO THE NORTH ACROSS THE NORTHERN BIG HORN BASIN AND JOHNSON COUNTY AROUND 18Z TUESDAY. AS THIS FRONT TRACKS SOUTH...MVFR CONDITIONS ARE EXPECTED TO DEVELOP AT KCOD BY 19Z WITH THESE CONDITIONS SPREADING SOUTH TO KCPR BY 22Z. KWRL...KRIW AND KLND WILL HAVE MAINLY VFR CONDITIONS THROUGH TUESDAY. && .FIRE WEATHER... A STORM SYSTEM WILL SPREAD SNOW INTO THE SOUTHWEST PART OF THE DISTRICT THIS EVENING AND SPREAD THROUGHOUT THE REST OF THE WEST BY MIDNIGHT. ON TUESDAY...WIDESPREAD SNOW IS EXPECTED IN THE WEST WITH THE CHANCE OF RAIN OR RAIN AND SNOW MIXTURE INCREASING EAST OF THE DIVIDE. A COLD FRONT WILL SHIFT WINDS TO THE NORTH ACROSS THE NORTHERN PART OF THE DISTRICT TUESDAY MORNING WITH GUSTY WEST WINDS TO THE SOUTH REMAINING. ANOTHER COLD FRONT WILL PUSH SOUTH TUESDAY NIGHT INTO WEDNESDAY WITH ANOTHER INCREASED CHANCE OF SNOW FROM BUFFALO TO CASPER. && .RIW WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...SKRBAC LONG TERM...AR AVIATION...LIPSON FIRE WEATHER...SKRBAC