Sunrise 5:42 AM   Sunset 8:12 PM Moonrise 2:42 PM   Moonset 2:19 AM

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FXUS65 KREV 181514 AFDREV

Area Forecast Discussion National Weather Service Reno NV 157 AM PDT Sat May 18 2024

SYNOPSIS

Unseasonably warm temperatures along with afternoon breezes will persist through Saturday. Shower and thunderstorm chances return for the Eastern Sierra this afternoon and for areas south of Highway 50 on Saturday. The weather pattern shifts late Sunday bringing cooler temperatures, enhanced winds and potential for intermittent wet weather next week.

DISCUSSION

Quick Points:

* Daytime highs will continue to run 5-15 degrees above average through today. A cooling trend will follow Sunday into next week with temperatures hovering near to slightly below seasonal averages by Monday and Tuesday.

* Typical afternoon breezes develop daily through the weekend with brief periods of locally choppy conditions on area lakes during the late afternoons hours.

* Although generally dry conditions will prevail across much of the region, look for a 20-30% chance for the return of thunderstorms and showers this afternoon for areas south of Hwy 50 to include western Nevada west of US-95.

(Today)

Although the passage of weak cold frontal boundary the day earlier brought a slight dip in temperatures, they will stay a bit above normal today. The most notable drop of temperatures will come Sunday into Monday with daytime highs and overnight lows lowering.
Regardless of the temperature drop, look for the westerly zephyr winds (gusts up to 30 mph) to return this afternoon and again Sunday afternoon.

Any shower and thunderstorm development will be preceded by the early development later this morning of cumulus over higher complex terrain from the Lake Tahoe Basin south along higher terrain areas of the eastern Sierra from Alpine County south to Mono County. The colder air aloft that is following in the wake of the cold front exiting southward into southern Nevada and will assist in the early initiation of any storms. As the typical westerly afternoon winds reaches maximum strength around 1-2PM, shower and thunderstorm coverage will roll eastward into western Nevada areas south of Highway 50. Most current CAPE EFI shift of tails guidance continues to show a decent signal for areas along the Sierra from Tahoe southward into Mono County.

* If you're outdoors recreating or working this afternoon in and around those areas be aware of when the these clouds mature vertically. This will be your initial sign for the future development of showers and isolated thunderstorms. Always remember when thunder roars, go indoors or when you see a flash, dash inside.

(Sunday Onward)

By Sunday into Monday, ensemble clusters have been trending toward the long-wave trough pattern deepening into the Great Basin. This trend in the ensemble simulations show further cooling along with continued north to possible northeast breezes. With the unseasonably cooler temperatures and an increased flux of Pacific moisture, blended guidance has set a large spread in probabilistic forecast temperatures, which in turn signals increased uncertainty in the depth and westward extent of the trough's influence into the region. There is medium confidence that Monday will be the coolest day of the upcoming week with temperatures once again resettling around seasonal averages the remainder of next week. -Amanda

AVIATION

* VFR conditions will generally persist for main terminals through the forecast period. Light winds during the morning hours with typical westerly afternoon breezes gusting to 20-25 kts for all terminals. FL100 winds gusting at times from the west to 20-25kts will shift gradually from the northwest and increase to 30-35kts after 00-03z . Afterwards, look for periods of light chop and LLWS below 2000 feet.

* Look for cumulus buildups developing across higher terrain later this morning. Thunderstorm and shower chances will then increase to 20-30% along the Sierra by 18-20z, and shift eastward into western NV after 20-22z. -Amanda

HYDROLOGY

Unseasonably warm daytime temperatures and mild nights, combined with higher solar angles, longer days, and limited cloud cover will continue to increase snowmelt rates through the weekend. Even the higher elevation deeper snow areas have begun to melt in earnest.

This rapid melt will lead to elevated flows with rivers and streams running cold and fast, most notably in areas draining significant terrain over ~7500 feet from Lake Tahoe south through Mono County.
Rivers and streams in this area will remain high through the weekend, with the highest flows likely through Saturday. Cooler temperatures and a depleting snow-covered contributing area will help reduce flows by Sunday into early next week. For areas in the Eastern Sierra, runoff may not taper off until Sunday or Monday when the cooler temperatures finally arrive.

While these high and cold flows can be hazardous to recreationalists, flooding is very unlikely. Please use extra caution around local rivers and streams which will be running fast and cold and can be very hazardous if entered. Remember the highest flows are significantly lagged from the heat of the day and can often occur at night.

Consistent and steady high flows will continue along the Lower Humboldt, with additional rises likely later in May or early June.

TB

REV Watches/Warnings/Advisories
NV...None.
CA...None.

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