057
FXUS65 KREV 210930
AFDREV
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
230 AM PDT FRI AUG 21 2026
KEY MESSAGES
* A DOWNWARD TEMPERATURE TREND STARTS TODAY WITH SEASONAL
TEMPERATURES EXPECTED BY EARLY NEXT WEEK.
* INCREASING WESTERLY GUSTS TODAY AND SATURDAY LEAD TO ELEVATED
TO NEAR CRITICAL FIRE CONDITIONS FOR NORTHEAST CA AND NORTHWEST
NV.
* ISOLATED SHOWER AND THUNDERSTORM POTENTIAL RETURNS FOR THE NV
BASIN AND RANGE, AND SOUTH OF US-50 THIS AFTERNOON INTO THE
WEEKEND.
DISCUSSION
THE BROAD UPPER-LEVEL RIDGE OVER THE FOUR CORNERS REGION WILL
CONTINUE TO INFLUENCE THE WEATHER PATTERN, MAINTAINING A SOUTHERLY
FLOW OF MONSOONAL MOISTURE INTO THE REGION. A WEAK UPPER-LEVEL
TROUGH WILL MOVE ACROSS NORTHERN CALIFORNIA AND OREGON TODAY
THROUGH SATURDAY, BRINGING INCREASED WINDS AND SLIGHTLY MODIFYING
THE AIRMASS, THOUGH TEMPERATURES REMAIN ABOVE SEASONAL AVERAGES.
TEMPERATURES WILL BE SLOWLY DECREASING THIS WEEKEND WITH AFTERNOON
HIGHS IN THE 90S FOR WESTERN NV/NE CA, AND UPPER 70S TO MID 80S
FOR SIERRA COMMUNITIES.
WEST TO SOUTHWEST WINDS WILL INCREASE ACROSS THE REGION THIS
AFTERNOON AND PEAKING ON SATURDAY. AFTERNOON GUSTS OF 25-35 MPH
ARE EXPECTED, PARTICULARLY FOR NORTHEASTERN CALIFORNIA AND
NORTHERN WASHOE COUNTY, WITH ISOLATED GUSTS UP TO 40 MPH POSSIBLE
IN EXPOSED AREAS. THESE CONDITIONS, COUPLED WITH LOW RELATIVE
HUMIDITY, WILL LEAD TO ELEVATED TO CRITICAL FIRE WEATHER
CONDITIONS, ESPECIALLY ON SATURDAY.
MONSOONAL MOISTURE WILL CONTINUE TO ADVECT NORTHWARD INTO THE
REGION, WITH PWAT VALUES AROUND 0.6-0.8 INCHES. THIS MOISTURE,
COMBINED WITH DAYTIME HEATING, WILL LEAD TO ISOLATED SHOWERS AND
THUNDERSTORMS. CHANCES ARE LOW (1-10%) TODAY AND CONFINED TO THE
EASTERN SIERRA AND WESTERN NEVADA BASIN AND RANGE. BY SATURDAY,
CHANCES INCREASE TO 10-40% AND BECOME MORE WIDESPREAD, ESPECIALLY
FOR THE EASTERN SIERRA AND THE NEVADA BASIN AND RANGE. INSTABILITY
REMAINS WITH MARGINAL MUCAPE 100-500 J/KG, BUT STRONG DCAPE TO
1000 J/KG, SUGGESTING THAT ANY STORMS COULD PRODUCE GUSTY OUTFLOW
WINDS UP TO 40 MPH, BRIEF HEAVY RAIN, SMALL HAIL AND FREQUENT
LIGHTNING. ON SUNDAY, CONDITIONS BEGIN TO DRY OUT SLIGHTLY, WITH
LOWER CHANCES FOR CONVECTION 10-20% ACROSS THE NV BASIN AND RANGE.
THE PATTERN NEXT WEEK REMAINS DOMINATED BY A PERSISTENT UPPER-LEVEL
RIDGE OVER THE SOUTHWEST AND A LONGWAVE TROUGH IN THE PACNW. THIS
WILL CONTINUE TO SUPPORT SEASONAL TEMPERATURES. HIGHS WILL
GENERALLY REMAIN IN THE LOW TO MID-90S FOR WESTERN NV AND NORTHEAST
CA VALLEYS, AND IN THE UPPER 70S TO MID-80S FOR SIERRA COMMUNITIES.
MONSOONAL MOISTURE WILL CONTINUE TO STREAM NORTHWARD AROUND THE
WESTERN FLANK OF THE RIDGE, LEADING TO VERY LOW CHANCES (~5%) OF
ISOLATED, DIURNALLY-DRIVEN SHOWERS AND THUNDERSTORMS, PRIMARILY
OVER THE HIGHER TERRAIN AND NV BASIN AND RANGE.
-HC
AVIATION
VFR CONDITIONS CONTINUE WITH MID TO HIGH LEVEL CLOUDS THROUGH THE
FORECAST PERIOD. SHRA/TSRA HAS A 5-10% CHANCE TO DEVELOP NEAR
KMMH/KHTH/KBAN THIS AFTERNOON, INCREASING TO 10-20% FOR SATURDAY.
WINDS INCREASE THIS AFTERNOON WITH WESTERLY GUSTS TO AROUND 25
KTS. THEN ON SATURDAY GUSTS POTENTIALLY INCREASE TO 30-35 KTS IN
THE AFTERNOON.
-HC
FIRE WEATHER
* ELEVATED FIRE RISK TODAY WITH AN INCREASE OF WEST TO SOUTHWEST
WINDS OF 20-30 MPH AND MIN RH OF 10-20% FOR EASTERN LASSEN, THE
SURPRISE VALLEY, NORTHERN WASHOE, THE SIERRA FRONT, AND PORTIONS
OF MONO COUNTIES. CONDITIONS DETERIORATE TO CRITICAL BY SATURDAY
OVER NORTHEAST CA AND NORTHWEST NV WITH GUSTS TO 30-35 MPH WITH
A 10-60% CHANCE OF EXCEEDING 40 MPH IN ISOLATED LOCATIONS
INCLUDING THE SURPRISE VALLEY, AND SIMILAR MIN RH COMPARED TO
FRIDAY. CRITICAL CONDITIONS ARE EXPECTED TO LAST FOR 3-6 HOURS
BETWEEN SATURDAY AFTERNOON AND EARLY EVENING. FOR THESE REASONS,
WE ISSUED A FIRE WEATHER WATCH FROM 11 AM THROUGH 11 PM
SATURDAY FOR NORTHERN WASHOE AND EASTERN LASSEN COUNTIES, AND
SURPRISE VALLEY IN MODOC COUNTY. OTHER AREAS IN WESTERN NV AND
MONO COUNTY WILL SEE GUSTS OF 25-30 MPH ON SATURDAY, CREATING
ELEVATED FIRE WEATHER CONDITIONS IN THE AFTERNOON.
-HC/HRICH
REV WATCHES/WARNINGS/ADVISORIES
NV...FIRE WEATHER WATCH FROM SATURDAY MORNING THROUGH SATURDAY
EVENING NVZ458.
CA...FIRE WEATHER WATCH FROM SATURDAY MORNING THROUGH SATURDAY
EVENING CAZ270-278.
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