Area Forecast Discussion
Issued by NWS Reno, NV
Issued by NWS Reno, NV
637 FXUS65 KREV 240939 AFDREV Area Forecast Discussion National Weather Service Reno NV 239 AM PDT Mon Jun 24 2024 .SYNOPSIS... * It is going to be warm and breezy through much of the week with temperatures easing a bit but still slightly warmer than average. Winds will be strongest Wednesday and Thursday. * There is a 10-30% chance of showers and thunderstorms south of Highway 50. Best chances will be on Tuesday. * Temperatures will remain very warm next weekend with typical afternoon breezes and little chance for precipitation. These conditions are likely to persist into the first week of July. && .DISCUSSION... * A trough pattern over the PacNW and ridge over the southern Rockies will continue to bring a rather breezy pattern to the area this week with temperatures cooling a few degrees by Thu- Fri. The trough advances eastward through the northern Rockies/ northern Great Basin Wed-Thu as another trough upstream drops southeastward through the Gulf of Alaska. This will bring a period of enhanced southwest winds Wednesday, shifting to the northwest behind a frontal system on Thursday. Some chop can be expected on area lakes this week, but a period of rougher lake waters, aviation turbulence and fire weather concerns is likely Wed-Thu as ridge gusts reach 60+ mph and we see gusts 30-45 mph at times for lower elevations. This pattern has been fairly consistent the past few days and overall confidence is above average. * One thing that continues to evolve is the transport of moisture around the periphery of the ridge into the eastern Sierra and western NV with latest guidance a bit farther north. Confidence is certainly below average on this aspect as we have pushed the chance for showers/storms to I-80 Tuesday with a few showers reaching Mono-Mineral counties as early as this evening. Extensive cloud cover may limit instability and forcing is rather diffuse. So we may end up with a lot more clouds and showers tonight and Tuesday than storms. Right now, the best chances for thunderstorms will be Tuesday afternoon as low level convergence increases ahead of incoming trough. The moisture may also have ramifications for fire weather as guidance shows dewpoints rising considerably. More below in the fire section. * For Friday and beyond, things look to go back to dry and very warm with typical daytime breezes. The upstream trough mentioned above moves into the PacNW, keeping a dry southwest flow aloft over the region and confining any monsoon push to our east. These conditions may very well persist into the July 4th weekend based on latest ensemble clusters. Like this week, we cannot rule out a period of enhanced winds as northern stream energy allows troughs to brush the Great Basin. Hohmann && .AVIATION... * Some subtropical moisture will stream into the Sierra and western NV later today through Tuesday and increase the risk of showers and thunderstorms, especially for areas south and east of the Tahoe Basin (including KMMH). There is a 10-20% chance at KMMH late this afternoon/evening then storms may move as far north as I-80 midday Tuesday before getting shunted eastward later in the day (KLOL-KNFL). * Afternoon/evening breezes will continue today and Tuesday with most gusts 20-25 kts and a 2-3 hour window of gusts 25-30 kts. Ridge winds were gusting to 50+ kts at times, so expect periods of light to occasionally moderate turbulence and even some LLWS during the early morning hours. * A cold front will bring more widespread winds, turbulence and LLWS Wed-Thu. Hohmann && .FIRE WEATHER... * Dry and breezy conditions again this afternoon/evening. Late Sunday, we saw locally critical fire weather conditions in fire zone 423. It will be similar today with the best combination of wind and low RH extending from the Sierra Front zone 420 to the West Humboldt Basin zone 423 where there will likely be a 2-4 hour period of near critical wind/RH. * Models continue to advance moisture northward into the eastern Sierra and western NV tonight and Tuesday with latest guidance a bit farther north. We have introduced a low-end chance of lightning near Mammoth Lakes and the White Mts late this afternoon (10-20% chance), but the best chance will be Tuesday as moisture streams northward and deepens. The one caveat will be instability as clouds thicken up and limited heating. Still, we believe there will be enough heating to get isolated storm coverage with best chances across Mono-Mineral-southern Lyon counties (15-30% chance) and more isolated elsewhere. It will continue breezy over northwest NV where drier air will remain in place for locally critical fire weather (north of I-80). * Our big concern will be Wed-Thu as the next trough approaches and southwest winds increases with widespread gusts 25-35 mph. The most critical areas will be in fire zones 278-458-423 where RH levels will be low enough (10-15%) for critical conditions. For Zone 420, RH levels look to stay up around 20%, but any change could quickly push the Sierra Front into critical fire weather. After additional coordination with the area GACCs later this morning, a watch issuance is likely (70% chance). On Thursday, gusty north winds and very dry air may bring portions of the Basin and Range (especially south of Hwy 50) the near critical levels behind the front. Hohmann && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$