220
FXUS65 KREV 290903
AFDREV
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
203 AM PDT TUE JUL 29 2025
KEY MESSAGES
* SHOWERS AND SCATTERED THUNDERSTORMS EXPECTED IN THE AFTERNOON
THROUGH THE EVENING POSE A RISK OF HEAVY RAIN AND FLOODING,
GUSTY OUTFLOW WINDS, SMALL HAIL, AND FREQUENT LIGHTNING.
* THUNDERSTORM ACTIVITY CONTINUES INTO THE OVERNIGHT HOURS THROUGH
WEDNESDAY MORNING. STORMS RETURN ONCE MORE WEDNESDAY AFTERNOON.
* A DRYING TREND WILL LIMIT THUNDERSTORMS THURSDAY WITH
INCREASING BREEZES POSSIBLE OVER THE WEEKEND.
DISCUSSION
ANOTHER SHORTWAVE TROUGH PASSING BY WILL GIVE US ANOTHER ROUND OF
THUNDERSTORMS THIS AFTERNOON ACROSS WESTERN NV AND NORTHEASTERN CA.
THE POSITIONING OF THE SHORTWAVE PUTS A BROAD AREA OF UPPER LEVEL
DIVERGENCE OVER OUR CWA, WHICH WILL BE THE MAIN FORCING FOR THE
THUNDERSTORMS THIS AFTERNOON. SURFACE HEATING WILL HELP INITIATE
THESE STORMS AROUND 2-2:30 PM. THE MAIN AREA OF CONCERN TODAY WILL
BE FROM NORTHERN MONO COUNTY NORTHWARD THROUGH TAHOE AND RENO UP TO
NORTHERN WASHOE COUNTY, LASSEN COUNTY, AND AS FAR EAST AS PERSHING
COUNTY. CURRENT CHANCES FOR STORMS ARE 30-40% FOR AFOREMENTIONED
AREAS.
MULTIPLE CAMS ARE SHOWING STRONG, SCATTERED THUNDERSTORM ACTIVITY UP
NEAR SURPRISE VALLEY AND NORTHERN WASHOE THIS AFTERNOON. ANOTHER
HOT SPOT AMONG THE CAMS IS ALONG THE PINE NUT MOUNTAIN RANGE WITH
STORMS MOVING TO THE NORTHEAST. LOOKING THROUGH MODEL SOUNDINGS
FOR THIS AFTERNOON, PWAT VALUES WILL STAY STEADY AROUND 0.60",
MUCAPE AROUND 800-1000 J/KG WITH HIGHER AMOUNTS UP TO 1600 J/KG
ALONG THE SIERRA CREST, AND DCAPE AROUND 1500 J/KG. ALSO, RIGHT
AROUND 2 PM BEFORE CONVECTIVE INITIATION, SOME MODELS ARE SHOWING
A DRY SLOT AT 500 MB WHICH MAY HELP PROMOTE STRONGER UPDRAFTS AND
INCREASE HAIL SIZE. WITH THIS, I'D EXPECT IMPACTS TO BE SMALL
HAIL, TORRENTIAL RAINFALL, AND FREQUENT LIGHTNING. BASED ON THE
AMOUNT OF DCAPE, WIND GUSTS WILL LIKELY GET UP TO 55-60 MPH NEAR
ANY THUNDERSTORMS. OTHERWISE, THE SYNOPTIC-SCALE WINDS WILL BE
WESTERLY AND LIGHT UP TO 20 MPH.
THE CAMS ARE ALSO HINTING AT A 30% CHANCE FOR ELEVATED NOCTURNAL
THUNDERSTORMS TUESDAY NIGHT INTO WEDNESDAY MORNING FROM ALPINE
COUNTY NORTHWARD THROUGH TAHOE AND UP TO NORTHEASTERN CA. THE AXIS
OF THE LARGER SCALE TROUGH BECOMES NEGATIVELY TILTED OVERNIGHT,
PROMOTING THAT OVERNIGHT CONVECTION. THERE IS STILL QUITE A BIT OF
UNCERTAINTY IN THE MODELS FOR HOW STRONG THESE STORMS WILL BE. AS IT
STANDS RIGHT NOW, THERE'S A 15% CHANCE FOR LIGHTNING WITH THEM. MOST
OF THE MODELS HAVE THOSE STORMS GOING ALL THE WAY THROUGH THE
MORNING. THEN BY THE EARLY AFTERNOON HOURS WE'LL HAVE OUR NEXT ROUND
OF THUNDERSTORMS WEDNESDAY AFTERNOON. IT'LL BE INTERESTING TO SEE
HOW THE OVERNIGHT CLOUD COVER BEHAVES. IF THE STORMS PERSIST LONG
ENOUGH AND ARE POSITIONED FAR ENOUGH EAST OVER THE SIERRA, THEY
COULD INCREASE THE AMOUNT OF MIDDLE-HIGH LEVEL CLOUDS WHICH COULD
DELAY THE START OF THE CONVECTION WEDNESDAY AFTERNOON BY AN HOUR OR
TWO, DUE TO THE LACK OF SURFACE HEATING.
WEDNESDAY WE WILL SEE INCREASED STORM CHANCES OF 50-60% FOR MUCH OF
THE SAME AREAS AS WE'LL SEE TODAY. AFTER WEDNESDAY AS THIS TROUGH
LIFTS FURTHER NORTH, WE GET SOME RESPITE FROM THE THUNDERSTORMS AND
DRY OUT THROUGH THE END OF THE WEEK.
-JUSTIN
AVIATION
A 30-40% CHANCE OF SHOWERS AND THUNDERSTORMS MAY IMPACT
KRNO/KCXP/KMEV/KNFL THROUGH THE AFTERNOON BEFORE SUBSIDING AROUND 03-
04Z. EXPECT OUTFLOW GUSTS OF 50+ KTS, SMALL HAIL, FREQUENT
LIGHTNING, AND HEAVY DOWNPOURS REDUCING CIGS/VIS TO MVFR CONDITIONS
AT TIMES.
THUNDERSTORM ACTIVITY MAY CONTINUE OVERNIGHT INTO WEDNESDAY
MORNING FOR KTRK/KTVL AND TERMINALS ALONG THE SIERRA FRONT.
THUNDERSTORMS RESUME WEDNESDAY AFTERNOON FOR MUCH OF THE SAME
AREAS AS THIS AFTERNOON. ASIDE FROM STORMS, LIGHT WESTERLY
AFTERNOON BREEZES PREVAIL WITH LIGHT FL100 WINDS AND PARTLY SUNNY
SKIES.
-JUSTIN
FIRE WEATHER
THUNDERSTORM COVERAGE AND LIGHTNING DENSITY INCREASES TODAY,
ELEVATING THE POTENTIAL FOR NEW IGNITIONS REGIONALLY. HOWEVER,
THERE ARE COMPETING FACTORS THAT LIMIT CONFIDENCE IN THE OVERALL
LIGHTNING THREAT FOR MIDWEEK. ABUNDANT LIGHTNING IS BECOMING MORE
PROBABLE EACH AFTERNOON, PARTICULARLY IN NORTHEAST CALIFORNIA AND
NEAR THE OREGON BORDER WHERE THUNDERSTORM COVERAGE IS FAVORED TO
BE GREATEST. STORM MOTIONS WILL ALSO BE MODERATE, REDUCING THE
RESIDENCE TIME OF RAIN CORES OVER ANY LIGHTNING START. TO MAKE
MATTERS MORE COMPLICATED, THERE IS THE POSSIBILITY OF NOCTURNAL
LIGHTNING THIS EVENING INTO WEDNESDAY MORNING FROM THE TAHOE BASIN
NORTHWARD AS THE LOW PASSES OVERHEAD.
WITH ALL THAT BEING SAID, THUNDERSTORMS WILL TREND ON THE WETTER
SIDE OWING TO RICH MOISTURE ALOFT. FURTHERMORE, THE AREAS NEAR THE
OREGON BORDER HAVE RECEIVED CONSIDERABLE RAINFALL OVER THE LAST
SEVERAL DAYS, KEEPING FUELS SATURATED. THE MAIN TAKEAWAY IS THAT
INCREASING LIGHTNING PRODUCTION FROM WETTER THUNDERSTORMS IS
EXPECTED TODAY AND WEDNESDAY, AND MAY RESULT IN NEW IGNITIONS
AWAY FROM RAIN CORES.
-SALAS
REV WATCHES/WARNINGS/ADVISORIES
NV...NONE.
CA...NONE.
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