272
FXUS65 KREV 171933
AFDREV
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
1233 PM PDT WED SEP 17 2025
KEY MESSAGES
* WARM, SUNNY, AND DRY WEATHER TODAY, WITH SEVERAL DEGREES OF
COOLING LATER THIS WEEK.
* PATTERN SHIFT STARTS THURSDAY, BRINGING CHANCES FOR SHOWERS AND
THUNDERSTORMS THROUGH SATURDAY.
* RELATIVELY DRY START TO EARLY NEXT WEEK WITH ANOTHER WEATHER SYSTEM
POSSIBLE AS EARLY AS TUESDAY.
DISCUSSION
TODAY WILL BE THE WARMEST DAY OF THE NEXT WEEK WITH HIGHS PUSHING
THE LOW 90S IN VALLEYS OF W NV AND NE CA WHILE SIERRA COMMUNITY
COUNTERPARTS CAN EXPECT HIGHS IN THE LOW-TO-MID 80S. DRY
CONDITIONS WILL PREVAIL THROUGH THE REST OF TODAY BEFORE A PATTERN
SHIFT IN THE FORM OF TROPICAL MOISTURE FROM FORMER TROPICAL STORM
MARIO GETS SHUTTLED INTO THE AREA.
THE INFLUX OF MOISTURE WILL BRING DAILY CHANCES FOR SHOWERS AND
THUNDERSTORMS TOMORROW THROUGH SATURDAY. HREF CAMS CURRENTLY HAVE
VERY LITTLE AGREEMENT WITH BOTH THE TIMING AND THE SPATIAL
COVERAGE OF THOSE SHOWERS AND THUNDERSTORMS THURSDAY. FURTHERMORE,
CLUSTER GUIDANCE IS HAVING DIFFICULTY PINPOINTING HOW THE LOW
PRESSURE WILL PROGRESS. SOME MODELS HAVE THE LOW HANGING MORE OFF
THE COAST OF SOUTHERN CA WHILE OTHERS BRING THE LOW CLOSER
INLAND. THESE "WOBBLES" HAVE BROUGHT A RELATIVELY HIGH AMOUNT OF
UNCERTAINTY, ESPECIALLY FOR BEING ONLY 24-48 HOURS OUT.
CURRENT SATELLITE IMAGERY SHOWS A THICK BAND OF CLOUDS, ASSOCIATED
WITH THE LOW, OVER SOUTH CENTRAL CA. AS TODAY PROGRESSES, WE WILL
SEE AN INCREASE IN CLOUD COVER MOVING IN FROM THE SOUTH. IF SAID
CLOUD COVER LINGERS INTO THE LATE MORNING HOURS TOMORROW, WE COULD
SEE A DECREASE IN AFTERNOON THUNDERSTORM CHANCES DUE TO THE LACK
OF SURFACE HEATING. AS OF NOW, THERE IS A 35-50% CHANCE FOR
SHOWERS, WHICH WILL START IN THE SIERRA OF MONO COUNTY BEFORE
PROGRESSING NORTHWARD AND ENCOMPASSING MUCH OF W NV AND THE
SIERRA. SHOWERS MAY ALSO LINGER OVERNIGHT AND INTO EARLY FRIDAY
MORNING.
RINSE AND REPEAT THOSE CLOUD COVER CONCERNS FOR FRIDAY; MODELS
ARE SUGGESTING UPWARDS OF 0.8 INCHES OF PWAT ACROSS THE AREA
FRIDAY, WHICH IS ABOVE THE 95TH PERCENTILE FOR OUR AREA BASED ON
SOUNDING CLIMATOLOGY. IT IS VERY POSSIBLE THAT WE WILL HAVE TOO
MUCH MOISTURE FRIDAY FOR THUNDERSTORM DEVELOPMENT. ADDITIONALLY,
FRIDAY LOOKS TO BE THE COOLEST DAY OF THE WEEK, WITH AFTERNOON
HIGHS IN THE MID-TO-UPPER 70S FOR VALLEYS AND THE UPPER 60S FOR
SIERRA COMMUNITIES. THIS MAY REDUCE THE AMOUNT OF SURFACE HEATING,
AND THUS INSTABILITY, NEEDED FOR THUNDERSTORMS. HOWEVER, FRIDAY
MAY SEE POSSIBLE FORCING DUE TO THE UPPER RIDGE CREEPING UP INTO
OUR AREA.
THIS LEAVES US WITH SATURDAY. PWAT VALUES ARE EXPECTED TO BE LOWER
THAN FRIDAY (0.5-0.6") AND THE EFI IS LIGHTING UP PARTS OF NV AND
THE SIERRA WITH CAPE. IF WE'RE CLEAR IN THE MORNING, IT'LL BE
MUCH EASIER TO GET THUNDERSTORMS TO FIRE. BUT, THIS FORECASTER IS
HESITANT TO SAY WHICH DAY WILL BE THE MOST IMPACTFUL (BETWEEN
FRIDAY AND SATURDAY). WE'RE GOING TO HAVE TO SEE HOW EACH DAY
UNFOLDS; THE ANTECEDENT CONDITIONS ARE JUST AS IMPORTANT, IF NOT
MORE SO, THAN VARIOUS FORECAST VARIABLES. TLDR: THERE WILL STILL
BE SHOWER AND THUNDERSTORM THREATS FOR BOTH DAYS, WHICH COULD
INCLUDE BRIEF HEAVY RAINFALL, GUSTY OUTFLOW WINDS, FREQUENT
LIGHTNING, AND SMALL HAIL. ADDITIONALLY, THE EASTERN SIERRA UP
THROUGH THE TAHOE BASIN IS IN AN AREA OF MARGINAL RISK (>5%) FOR
FLASH FLOODING DUE TO EXCESSIVE RAINFALL ON FRIDAY FROM THE
WEATHER PREDICTION CENTER.
DRIER CONDITIONS ARE EXPECTED HEADING INTO EARLY NEXT WEEK BUT A
SHORTWAVE TROUGH TUESDAY COULD BRING ANOTHER ROUND OF SHOWERS.
KEEP UP TO DATE AT WWW.WEATHER.GOV/RENO.
-GIRALTE
AVIATION
VFR CONDITIONS WITH GENERALLY LIGHT FLOW WILL PERSIST FOR ALL
TERMINALS TODAY. MODEL GUIDANCE HAS REDUCED THE POSSIBILITY FOR
SLANTWISE VISIBILITY CONCERNS FOR KMMH FROM SMOKE FROM THE GARNET
FIRE. CLOUD COVER WILL INCREASE TODAY AND EXPAND NORTHWARD THROUGH
TONIGHT. MIXED MODEL GUIDANCE HAS RESULTED IN LOW CONFIDENCE IN
THE TIMING FOR SHOWERS THURSDAY, BUT ISOLATED RAIN CHANCES CAN BE
EXPECTED TO IMPACT KMMH AFTER 18/21Z. SAID RAINFALL CHANCES ARE
EXPECTED TO PROGRESS NORTHWARD THURSDAY, IMPACTING ALL SIERRA AND
SIERRA FRONT TERMINALS BY 19/06Z.
-GIRALTE
REV WATCHES/WARNINGS/ADVISORIES
NV...NONE.
CA...NONE.
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