Area Forecast Discussion
Issued by NWS Reno, NV
Issued by NWS Reno, NV
078 FXUS65 KREV 130909 AFDREV Area Forecast Discussion National Weather Service Reno NV 209 AM PDT Thu Jun 13 2024 .SYNOPSIS... The region sees well above normal temperatures continuing today along with chances of showers and thunderstorms along and south of US-50 during the afternoon and evening hours. A dry cold front is expected to pass through the region on Friday making critical fire weather conditions likely during the afternoon. Cooler temperatures are favored this weekend and into the start of next week though the temperatures look to rebound a bit by midweek. && .DISCUSSION... The latest RAP analysis depicts an upper air ridge over the CWA with an upper air low residing to south off the coast of the Baja Peninsula this morning. Current satellite imagery shows mostly clear skies across the region with some scattered high clouds in western NV while current surface observations report dry conditions with light and variable winds. Going through the rest of today, models forecast the southern low moving across southern CA with the ridge progressing eastward. By Thursday night, models have the CWA between a ridge to the east, a new trough that has moved into the Pacific Northwest, and the southern low that has now moved over the southern tip of NV. At the surface, models show the region still with above normal temperatures though they may be a few degrees less than temperatures of the previous two days. As for precipitation chances: the SREF, HRRR, and NAM are showing around 15-25% chances for showers and thunderstorms for areas along and south of US-50 once again between 11 AM PDT through just before midnight PDT. These chances look to start in the Sierra portions of this area and then spread into the western NV portions during the afternoon. The latest QPF values range between a trace and around one tenth of inch with isolated portions of Mono County possibly seeing up to two tenths of an inch. While there are patches of triple digit MLCAPE in the possible precipitation areas, the RRFS does show around 1000 J/kg of MLCAPE in the higher elevation portions of Alpine and Mono Counties. Not anticipating severe weather, but would not be surprised if storms that develop in this area yield some small hail and gusty winds at times. By the afternoon and evening hours, models also show the westerly winds that could gust up to around 30-35 mph in some locations. Overnight lows look be in the 50s and 60s in western NV while the Sierra portions of the CWA may see low temperatures in the 40s and 50s. For Friday, model guidance shows the CWA with a west-southwesterly flow aloft as the trough in the Pacific Northwest moves in and pushes the other upper air features eastward. As a result of this upper air pattern, the CWA can expect a dry cold front passage which will usher in westerly to southwesterly winds gusting up to around 25-35 mph during the afternoon with the potential for up to around 40 mph in wind prone areas. This may create some choppy conditions across area lakes along with cross wind issues for high profile vehicles Friday afternoon. Temperatures in the CWA look to start to cool a bit on Friday with this cold front passage as well. The increased winds and dry conditions look to support several hours of critical fire weather within the region. Please refer to the Fire Weather Section of the discussion below as well as the current Fire Weather Watch product for more details. Over the weekend, latest ensemble guidance forecasts the upper air trough to move over the western CONUS allowing for the cooling trend to continue though orienting itself on Sunday night into Monday morning to give the CWA a southwesterly upper air flow. There are some mixed precipitation chances (15-25%) for portions of the CWA near the OR border during this time with a passing low pressure system in the northwestern CONUS though some uncertainty still exists. The axis of the trough looks to pass over the CWA causing the decrease in temperatures to continue for another day. On Tuesday, ensemble guidance shows a ridge moving into the Pacific Northwest before moving over the CWA on Wednesday and Thursday with the trough diminishing and moving to the northeast. Forecast models currently show a slight warming trend beginning Tuesday and going into the middle of the week as a result with minimal precipitation chances. -078 && .AVIATION... Upper ridging aloft will continue to bring predominately VFR conditions to regional terminals. Lighter terrain influenced winds will prevail overnight into the morning hours. The exception will be gusty afternoon winds with gusts to reaching to 20-25 kts for main terminals between 21-03Z. The primary weather concern will continue to be afternoon showers and isolated thunderstorms forming south of Highway 50 from the eastern Sierra, into Lyon and Mineral counties. Density altitude issues will also persist through Friday with limited relief arriving this weekend as cooler near normal temperatures filter into the region. -Amanda && .FIRE WEATHER... * Blended and ensemble guidance project a multi-hour period of criteria gusty winds and low RHs bringing critical fire weather conditions for the Sierra Front, N Washoe County, and the Basin and Range on Friday afternoon into the evening. * Sustained west to southwest winds of 15-20 mph with gusts of 25-35 mph will overlap with daytime humidities ranging 10-15%. These conditions coupled with abundant sunshine open a 3-6 hour window Friday afternoon. Overnight RH recoveries across western NV will also be quite poor from Friday into the weekend, especially from valley floors to mid-slope areas where maximum RHs struggle to exceed 40% for most areas. * The latest fuel intel from partners show receptive fine fuel beds exist in portions of the Basin and Range and below 6500 feet across the Sierra Front, but a sub-critical fuel status will likely preclude a greater fire concern in N Washoe County. Elevated to locally critical fire weather conditions may develop Saturday and Sunday afternoon, but strongest winds will be much weaker and more localized compared to Friday. -Salas/Amanda && .REV Watches/Warnings/Advisories... NV...Fire Weather Watch from Friday afternoon through Friday evening NVZ420. Fire Weather Watch from Friday afternoon through Friday evening NVZ423. CA...&& $$