706 FXUS65 KREV 270403 AAA AFDREV Area Forecast Discussion...UPDATED National Weather Service Reno NV 903 PM PDT Wed Jul 26 2017 .UPDATE... Thunderstorms are winding down with some showers and an isolated thunderstorm or two near and east of Highway 95. A quick update to reflect the current trends. Otherwise, a bit of a break tomorrow before thunderstorms increase again for the weekend. Looking at the latest models, there could be an isolated storm or two tomorrow over the Sierra Crest in Mono County, but will let the mid shift make that decision. Wallmann && .PREVIOUS DISCUSSION... /Issued 149 PM PDT Wed Jul 26 2017/ SYNOPSIS... Thunderstorms are once again developing across northeast California and northwest Nevada this afternoon and are expected to continue into the evening. A drier air mass works into the region overnight with tranquil weather expected for Thursday. Isolated storms will return on Friday with increasing thunderstorm coverage possible heading into the weekend. Near average high temperatures rise to above average for Friday and the weekend. SHORT TERM... The upper level low which had been sitting off the northern California coast the past few days is shifting inland today. This is bringing increasing upper level divergence with thunderstorms already ongoing along the leading edge of the low. There is plenty of lingering moisture and instability with the shear across the region potentially helping storms to become organized. Locally severe storms are once again possible. Storm motions will be fast, but there is also still high PWATs across the region, likely leading to a hybrid of locally heavy rain and the potential for new fire starts from lightning. Flash flooding is less likely due to storm motion, however, if storms train over the same region or produce intense rainfall rates over steep terrain or recent burn scars, it is not out of the question. The other concerns today are the potential for some larger hail in addition to accumulation smaller hail and gusty and erratic outflow winds over 50 mph. Isolated nocturnal storms may linger across central Nevada into eastern Nevada overnight, but overall there will be a drier and more stable airmass moving into the region behind the upper low. This will likely keep any storms from developing on Thursday. This break is short lived, however, as moisture once again advects northward around an area of high pressure bringing the return of isolated thunderstorms on Friday. What will need to be watched is how this interacts with a weak upper wave off the California coast. It is possible this could enhance the thunderstorm coverage, but will leave the forecast alone for now with slight chances mainly south of Highway 50 on Friday. -Dawn LONG TERM...Saturday through Wednesday... Upper level ridge expands westward across the southwest for the weekend into the early part of next week, bringing a warm up in high temperatures and potentially another push of modified monsoonal moisture. Signals are a bit mixed as far as how much moisture advects northward, with some operational runs as high as 0.80-1.0" PWATs, while others are more in the 0.5-0.75" range. Either way, it looks like thunderstorms will continue Saturday, with coverage increasing Sunday into Monday. If PWATs end up pushing the upper end of the range, it does increase the flash flood potential, but keep in mind this is only one possible scenario. There is a chance that another weak low may move into northern California on Tuesday, which would keep thunderstorm chances in the forecast, but could change the character of the storms. -Dawn AVIATION... Thunderstorms are firing off across northeast California and northwest Nevada again today. Storms will bring localized heavy rainfall, creating short-lived periods of IFR CIGS/VIS and obscuring terrain. Abundant lightning, small hail, gusty and erratic winds, blowing dust, and turbulence are also concerns. The greatest thunderstorm coverage is expected to be north of Interstate 80 this afternoon and evening, though isolated thunderstorm cells are possible elsewhere across the region. Chances for a storm to affect a terminal site: KRNO/KCXP: 20 percent KMMH/KTRK/KTVL: 10 percent A drier air mass moves into the region overnight into Thursday with storms not expected on Thursday. This will be short-lived, however, with additional thunderstorm chances for the weekend. -Dawn && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$ For more information from the National Weather Service visit... http://weather.gov/reno |