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199 FXUS65 KREV 220931 AFDREV Area Forecast Discussion National Weather Service Reno NV 231 AM PDT Mon Jul 22 2024 .SYNOPSIS... * Daily thunderstorm chances through Thursday. Storms trending wetter with increased chances for localized heavy rainfall and flash flooding. * Continued moderate-major HeatRisk through Tuesday with highs 100-105 for northwest-west central NV. * A cooling trend arrives later this week with highs returning to near average. Overall drier and breezier conditions expected. && .DISCUSSION... An active thunderstorm day brought pockets of heavy rainfall and localized flooding, with harder hit areas including the Hidden Valley area of SE Reno, I-80 near USA Parkway, US-50 around Dayton, southern Douglas County and central Mono County. A few wind sensors in west central NV reported possible outflow gusts of 70+ mph. We'll see near-repeat thunderstorm activity for the next three days, as plentiful moisture and upper level disturbances continue to rotate around a high pressure ridge centered over the central and eastern Great Basin. For today, storms are most likely to begin over the eastern Sierra/Tahoe basin and western NV south of US-50, then spread north and east into the remainder of western NV. High PW values (0.80-1.1") and slow cell motions bring the potential for locally heavy rainfall and flooding again, although some areas especially south of US-50 may end up over-developing cloud cover with an early end to most convection, while storms farther north transition to more outflow-dominated activity. Increased lightning activity will generally be accompanied by plenty of rainfall, but parts of far northeast CA/northwest NV may see faster moving cells and isolated dry lightning strikes with lower PW values (0.60-0.80"), as a shortwave brushes across the Pacific NW. Tuesday's storm activity looks to be more focused across areas south of US-50, although some cells could push northward into the main urban areas along I-580/US-395 and across Lyon County, with more isolated cells farther north to near the OR border. Wednesday is showing the deepest moisture overall, with PW values ranging from 0.90-1.25". While this could enhance the risk for more heavy rainfall and flooding (especially in areas where notable rain fell Sunday or occurs today-Tuesday), the thicker cloud cover could also reduce the coverage of convection as the afternoon progresses. By Thursday, the thunderstorm potential shifts farther south and east, mainly from west central NV near/east of US-95 southward to Mono County. With a longwave trough edging closer to the west coast, storms are more likely to be faster moving while drier air with increasing SW-W winds spreads across the remainder of the region. Then from Friday through early next week, dry conditions are expected to prevail regionwide, with the best potential for enhanced afternoon winds (gusts 30-35 mph) on Friday. Temperatures this week will begin above average, although today's increased cloud cover could shave a couple degrees from recent days' highs, including the Heat Advisory area. Tuesday looks to have a rebound with highs close to 105 degrees again in the advisory area, before edging downward again by midweek. A more notable cooling will begin Thursday, with highs settling into the lower 90s for lower elevations and upper 70s-lower 80s for Sierra communities by next weekend. MJD && .AVIATION... * Afternoon shower and thunderstorm chances (30-40%) will prevail across the main terminals today mainly from 20-03Z. These storms will be capable of producing MVFR/IFR conditions with periods of heavy rainfall, small hail, frequent lightning, and outflow gusts 30-40 kt. * For west central NV today, outflow gusts of 45+ kts could produce sudden reductions to visibility, due to areas of blowing dust downwind of desert sinks and dry lake beds, mainly from 00-04Z. * T-storm chances on Tuesday increase to 50-60% for KMMH, but decrease to 15-30% for the Tahoe area and far western NV terminals. The highest overall storm chances for this week are expected Wednesday, around 60% for KMMH and 30-45% for the Tahoe area and far western NV terminals. MJD && .REV Watches/Warnings/Advisories... NV...Heat Advisory until 8 PM PDT Tuesday NVZ004-005. CA...None. && $$