textproduct: Reno

KEY MESSAGES

* Warmer than average temperatures persist today, then much cooler conditions are expected from Tuesday through late week. * Gusty winds will bring aviation, recreation, and fire weather concerns today and Tuesday.

* Shower and isolated thunderstorm chances forecast today, but return on Tuesday with the highest overall chances Wednesday through Thursday.

DISCUSSION

The latest RAP analysis of the upper air pattern shows an upper low off the coast of southern BC today. Model guidance projects this low tracking down to over the WA coast late today. At the surface, models are showing a tightening pressure gradient through the day ahead of an approaching cold front currently near the WA/OR coast. This means that increased winds will be responsible for some concerns in the CWA today. The forecast is showing west to southwest winds picking up in the afternoon in NE CA and NW NV with gusts up to around 40-45 mph. Lake Wind Advisories (including Lake Tahoe and Pyramid Lake) and Red Flag Warnings have been issued for the areas today where the fire weather and wind concern are the greatest. Please see the products for more information, but please keep these winds in mind if you have any Memorial Day outdoor plans for later today. Blowing dust may also occur near desert sinks and playas in W NV with these winds. Elsewhere, winds look to gust up to around 25-35 mph. This will also be the last day for warmer temperatures ahead of the approaching cold front with the W NV valleys having daytime highs in the 80s and the Sierra communities having highs in the upper 60s to lower 70s. As for precipitation chances today, shower and isolated thunderstorm chances (~15%) look to be confined to south of US-50 today. The window has opened in Mono, S. Lyon, and W. Mineral Counties with spotty showers already popping up. Coverage will slowly spread northeast into more of W NV before ending around 9 PM this evening. Any storms should be sub-severe today, but please be weather aware in case a storm develops near your outdoor activities today. Overnight, Sierra ridge winds pick up quite a bit with gusts up to around 75-85 mph as the cold front continues its approach toward the region.

For Tuesday, model guidance has the cold front moving through the CWA as the upper low pushes across OR and over the CWA by Tuesday evening. Cooler daytime high temperatures are on tap as the forecast calls for highs around 5 to 15 degrees below late May normals. Increased winds (gusts up to around 30-40 mph) will continue on Tuesday though direction will shift to northwesterly behind the front. This will lead to a second day of Lake Wind Advisories within the region (refer to the product for details). Currently, precipitation chances (55-85%) are expected for NE CA and Northern Washoe County portions of the CWA during the morning and afternoon hours of Tuesday, but coverage then spreads into the Tahoe Basin as well as eastern portions of Pershing and Churchill counties by the evening hours. Snow levels still look to be around 6.5-7.5 kft so snow could be possibly mixed in with rain at higher elevations that see showers. As for thunderstorm chances, there is around a 20-25% chance that afternoon showers could contain some rumbles of thunder in Plumas, Sierra, Nevada, and S. Lassen Counties with adjacent counties seeing a ~15% chance. Models are showing around 100-200 J/kg of CAPE in these areas, so be prepared in case a storm develops near your location. Tuesday night lows will be colder due to the frontal passage with the NE CA and W NV valleys being in the middle 30s to lower 40s range and the Sierra communities dropping into the 20s.

For Wednesday and Thursday, the upper low will reside generally over the CWA though possibly wobbling around a bit. This will push in more cooler air from the north, dropping area high temperatures even more. W NV and NE CA valley will see highs in the upper 50s on Wednesday and in the 60s on Thursday. Sierra communities will have Wednesday's highs between the middle 40s and the lower 50s and Thursday's highs in the upper 40s to middle 50s range. More widespread shower coverage bringing rain and mountain snow to the CWA are to be expected on these two days as well. Snow levels are now forecast to drop to around 5.5-6 kft on early Wednesday morning, but gradually rise to around 7-7.5 kft during by the late afternoon. Snow levels more or less stabilize through Thursday morning before rising as the upper low moves east. The latest snowfall forecast shows the highest Sierra peaks around the Tahoe region with up to around 2 inches of snow and the Eastern Sierra peaks in Mono County seeing up to around 6 inches by Thursday afternoon. There is still low forecast confidence on these totals due to the uncertainty in the evolution of the upper low at this time, so will be monitoring how it pans out. Light accumulations will be possible at lower Sierra elevations, but not anticipating any impactful amounts at this time. While thunderstorms may be possible with the showers on Wednesday, Thursday currently sees more widespread and better chances (15-30%). Precipitation lingers into Friday followed by temperatures warming to closer to seasonal normals by the weekend. -078

AVIATION

VFR conditions are expected at all area TAF sites today and tonight. Winds are the main aviation impact today and going through the night. SW-W winds this afternoon will gust up to around 25-30 kt for western NV terminals and around 25 kt for the Sierra/Tahoe area terminals. KMMH may see some vicinity showers and isolated thunderstorms possible through 26/05Z. As FL100 winds still expect to increase tonight with gusts 60-70 kt, turbulence and periods of LLWS are likely, while gusts of 25-30+ kt could mix down to the surface at times, especially for KTVL/KTRK.

Windy conditions with turbulence and periods of LLWS continue on Tuesday as a cold front passes through the region. Winds shift to a W-NW direction for most terminals (KTVL sees SSW winds) with gusts up to around 25-30 kt once again. Otherwise, VFR conditions will prevail through Tuesday, followed by increased chances for rain showers Wednesday-Thursday that could bring MVFR conditions at times with terrain obscurations, although wind speeds will decrease. MJD/078

FIRE WEATHER

* Red Flag Warnings remain in effect through this evening for northeast CA and northwest NV, including Pershing County where the Quartz Fire continues to burn in the northeast part of that county. Minimum humidity levels will drop to 10-20%. Southwest to west winds ahead of an approaching cold front will be gusty going into the night.

* Uncertainty remains on the extent of vegetation that has dried out sufficiently, but information from local fire partners and the growth of the Quartz Fire suggests that areas of cured grasses and sagebrush will be capable of carrying fire in valleys/midslopes of far northwest NV. Farther south, elevated fire weather conditions will be present, but the latest fuel moisture data from local fire partners isn't showing widespread coverage of dry vegetation.

* Gusty winds return on Tuesday and shift to a more northwest direction, as a cold front sweeps through the region. Areas near and south of US-50 in west central NV, and the US-6 corridor in southeast Mono County could see a short duration of near-critical wind and humidity conditions Tuesday afternoon. Otherwise, temperatures cool and humidity rises behind the front on Tuesday, with increasing chances of showers and wetting rainfall Wednesday and Thursday. MJD/078

REV Watches/Warnings/Advisories

NV...Red Flag Warning until 11 PM PDT this evening NVZ458.

Lake Wind Advisory until 11 PM PDT this evening NVZ004.

Lake Wind Advisory until 2 PM PDT Tuesday NVZ002.

Lake Wind Advisory from 2 PM Tuesday to 5 AM PDT Wednesday NVZ001.

Lake Wind Advisory until 5 PM PDT Tuesday NVZ003.

Red Flag Warning until 11 PM PDT this evening NVZ423.

Lake Wind Advisory from 5 AM Tuesday to 11 AM PDT Wednesday NVZ004.

CA...Red Flag Warning until 11 PM PDT this evening CAZ270-278.

Lake Wind Advisory until 11 PM PDT this evening CAZ071.

Lake Wind Advisory until 2 PM PDT Tuesday CAZ072.

Lake Wind Advisory from 8 AM to 5 PM PDT Tuesday CAZ073.