AFDREV AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RENO NV 207 PM PDT THU AUG 22 2013 .SYNOPSIS... AREA OF LOW PRESSURE LIFTS NORTH INTO OREGON TONIGHT WITH THUNDERSTORM CHANCES ENDING AFTER THIS EVENING AS DRY AND STABLE SOUTHWEST FLOW MOVES INTO NORTHEAST CALIFORNIA AND NORTHWEST NEVADA. THIS WILL RESULT IN BREEZY AFTERNOON AND EVENING WINDS THE NEXT SEVERAL DAYS...WITH THE STRONGEST WINDS LIKELY THIS WEEKEND. AREAS OF SMOKE AND HAZE WILL CONTINUE ACROSS THE REGION DUE TO SEVERAL ONGOING WILDFIRES. && .SHORT TERM... ONLY MINOR CHANGES MADE TO ONGOING FORECAST WITH THE GREATEST CHANGE TO ADD SMOKE AND HAZE DUE TO MULTIPLE ONGOING WILDFIRES, THE GREATEST CONTRIBUTOR BEING THE RIM FIRE JUST WEST OF YOSEMITE. THE UPPER LEVEL LOW WHICH HAS BROUGHT US PLENTY OF THUNDERSTORMS THE PAST FEW DAYS IS BEGINNING TO LIFT NORTH WITH A DRIER SOUTHWEST FLOW RESULTING ACROSS NORTHEAST CALIFORNIA AND NORTHWEST NEVADA. THUNDERSTORMS ARE FIRING ONCE AGAIN THIS AFTERNOON, MAINLY NORTH OF A SUSANVILLE-LOVELOCK LINE, IN A DIFFLUENT AREA AS THE UPPER LEVEL LOW LIFTS INTO NORTHERN CALIFORNIA THIS AFTERNOON. UPPER LEVEL FLOW HAS INCREASED, CAUSING UNIDIRECTIONAL SHEAR, SO STORMS HAVE BEEN ABLE TO SUPPORT HAIL DEVELOPMENT. IN ADDITION, STORMS CAN PRODUCE GUSTY AND ERRATIC WINDS. DESPITE STORM MOTIONS OF 15 TO 20 MPH, STORMS SHOULD PREDOMINATELY BE WET AS LOW LEVEL MOISTURE AND PWATS REMAIN WELL ABOVE NORMAL. SOUTH OF INTERSTATE 80 A VISIBLE DRY SLOT AND AREA OF SUBSIDENCE CAN BE SEEN MOVING INTO THE REGION WHICH HAS STABILIZED THE AIRMASS. AN AREA OF LOW PRESSURE DIGGING SOUTH IN THE EASTERN PACIFIC WILL INCREASE THE GRADIENT THIS WEEKEND. GUSTY SOUTHWEST WINDS OF 25 TO 35 MPH CAN BE EXPECTED WHICH MAY COMBINE WITH LOW RELATIVE HUMIDITY ON SUNDAY TO MAKE FOR FIRE WEATHER CONCERNS. THE GREATEST FORECAST CONCERN AND CHALLENGE THE NEXT SEVERAL DAYS WILL BE THE AREAS OF SMOKE WHICH ARE AFFECTING THE REGION DUE TO ONGOING WILDFIRES. THE RIM FIRE HAS GROWN DRASTICALLY THE PAST 24 HOURS AND IS CURRENTLY ESTIMATED TO BE NEARLY 55,000 ACRES. THE SMOKE PLUME CAN BE CLEARLY SEEN ON BOTH SATELLITE AND RADAR SPILLING ACROSS THE SIERRA AND INTO WESTERN NEVADA. THE DIFFICULTY IS KNOWING HOW ACTIVE THE FIRE WILL BURN AND IF THE PLUME WILL BE LOFTED HIGH ENOUGH TO BE CARRIED BY UPPER LEVEL WINDS OR IF SMOKE WILL SETTLE INTO VALLEYS. HAVE BASED THE CURRENT SMOKE/HAZE FORECAST ON THE LATEST TRENDS AND HYSPLIT RUNS. HAVE ONLY INCLUDED SMOKE/HAZE IN THE FORECAST THE NEXT 48 HOURS DUE TO THE UNCERTAINTY IN FIRE BEHAVIOR THE NEXT SEVERAL DAYS, BUT IF IT CONTINUES TO BURN THIS ACTIVELY, EXPECT SMOKE TO TAKE A SIMILAR PATTERN AS SOUTH TO SOUTHWEST FLOW REMAINS OVER THE AREA. THE SPRING PEAK FIRE AND AMERICAN FIRE ALSO CONTINUE TO BURN, BUT ARE NOT PRODUCING AS LARGE OF A SMOKE PLUME AT THIS TIME. DJ .LONG TERM...SUNDAY THROUGH THURSDAY... NO MAJOR CHANGE TO GRIDS NEXT WEEK. EASTERN CALIFORNIA AND WESTERN NEVADA WILL REMAIN UNDER DRY SOUTHWEST FLOW AS A STRONG RIDGE REMAINS ANCHORED OVER THE CENTRAL CONUS AND A TROUGH REMAINS NEAR AND JUST OFF THE PACIFIC COAST. THE ONLY EXCEPTION WILL BE NORTH OF SUSANVILLE AND GERLACH SUNDAY WHEN A FAST-MOVING DISTURBANCE WILL MOVE THROUGH NORTHERN CALIFORNIA AND OREGON AND BRING INCREASING MOISTURE AND CLOUD COVER. THE BEST MOISTURE IS CURRENTLY PROGGED TO REMAIN WEST OF THE WARNER MOUNTAINS IN MODOC COUNTY SO FOR NOW THE FORECAST CALLS FOR PARTLY CLOUDY SKIES. HOWEVER, IF THE DISTURBANCE SHIFTS ANY FURTHER SOUTHEAST WE WILL HAVE TO ADD A SLIGHT CHANCE OF SHOWERS TO THE SURPRISE VALLEY/NORTHERN WASHOE COUNTY AND FAR NORTHERN LASSEN COUNTY. AFTERNOON HIGHS WILL STAY WITHIN A FEW DEGREES OF NORMAL FOR LATE AUGUST, MID 80S TO LOW 90S FOR WESTERN NEVADA AND MID 70S TO LOW 80S FOR THE EASTERN SIERRA. WITH THE TROUGH AND RIDGE SETTING UP A RATHER STEADY-STATE THERMAL GRADIENT WINDS SHOULD KICK UP EACH AFTERNOONS AND EVENING WITH PEAK GUSTS AT 25-30 MPH. SNYDER && .AVIATION... ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS HAVE DEVELOPED ONCE AGAIN THIS AFTERNOON NORTH OF A KSVE-KLOL LINE. GUSTY AND ERRATIC OUTFLOW WINDS, HAIL, AND LOCALLY HEAVY RAINFALL CAN BE EXPECTED WITH THESE STORMS. TERRAIN MAY BE OBSCURED WITH MVFR CIGS/VIS POSSIBLE IN THE HEAVIER SHOWERS. GREATEST IMPACT TO AVIATION THIS AFTERNOON AND EVENING, AND POTENTIALLY THE NEXT SEVERAL DAYS, IS SMOKE FROM ONGOING WILDFIRES, THE GREATEST CONTRIBUTOR BEING THE RIM FIRE JUST WEST OF YOSEMITE. THIS IS PRODUCING MVFR CONDITIONS FOR KRNO, KCXP, AND KTRK, WITH IFR CONDITIONS AT KTVL THIS AFTERNOON. EXPECT THE WEST WINDS THIS AFTERNOON TO HELP CLEAR SMOKE OUT A BIT, BUT VISIBILITY WILL STILL BE IMPACTED ACROSS THE SIERRA BETWEEN KTRK AND KBAN INTO MUCH OF WESTERN NEVADA. EXPECT TERRAIN OBSCURATION AND SLANTWISE VISIBILITY AS LOW AS A COUPLE MILES ON APPROACH TO AIRPORTS IN THIS REGION. DJ && .REV WATCHES/WARNINGS/ADVISORIES... NV...NONE. CA...NONE. && $$