990
FXUS65 KREV 131011
AFDREV
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
311 AM PDT THU AUG 13 2026
KEY MESSAGES
* SHOWERS AND THUNDERSTORMS BECOME WIDESPREAD THIS AFTERNOON WITH
PRIMARY RISKS OF HEAVY RAIN CAPABLE OF FLASH FLOODING AND
FREQUENT LIGHTNING, ALONG WITH OUTFLOW WIND GUSTS AND HAIL.
* ISOLATED SHOWERS AND THUNDERSTORMS MAY RETURN FRIDAY AFTERNOON
BUT WITH A MUCH LOWER RISK OF FLASH FLOODING.
* DRIER CONDITIONS PREVAIL THIS WEEKEND THROUGH EARLY NEXT WEEK
WITH TEMPERATURES A FEW DEGREES BELOW MID-AUGUST AVERAGES.
DISCUSSION
* AN AREA OF LOW PRESSURE OFF THE SOUTHERN CA COAST IS CURRENTLY
PRODUCING ISOLATED SHOWERS AND T-STORMS IN THE SAN JOAQUIN
VALLEY. THE MORE SOUTHERLY POSITION OF THIS LOW WILL KEEP MOST
FORCING THROUGH MID-MORNING SOUTH AND WEST OF THE SIERRA AND
WESTERN NV, WITH PRECIP LIMITED TO ISOLATED SHOWERS AND LESS
THAN 10% CHANCE OF LIGHTNING.
* BY LATE MORNING THROUGH EARLY AFTERNOON, THIS LOW THEN EJECTS
NORTHWARD TOWARD THE SIERRA, PROVIDING MORE SUBSTANTIAL FORCING
TO COMBINE WITH THE MOISTURE IN PLACE, WITH DECENT INSTABILITY
(CAPE VALUES BETWEEN 500-1000 J/KG). HIGHER RESOLUTION GUIDANCE
CONTINUES TO SUPPORT RAPID T-STORM DEVELOPMENT BETWEEN 10 AM-12
NOON FOR THE EASTERN SIERRA, THEN BETWEEN NOON AND 2 PM FOR FAR
WESTERN NV INCLUDING AREAS AROUND THE BUG AND STALLION FIRES.
THESE STORMS COULD DEVELOP INTO MORE PERSISTENT CLUSTERS AS THEY
MARCH ACROSS THE REMAINDER OF WESTERN NV THROUGH THE REST OF
THIS AFTERNOON, ALTHOUGH SOME AREAS WILL MISS OUT ON MORE
INTENSE RAINFALL DUE TO A BROADER CLOUD SHIELD SPREADING OUT
FROM THESE CLUSTERS AND REDUCING HEATING/INSTABILITY. ALTHOUGH
MOST OF THE CELLS ARE EXPECTED TO PUSH EAST OR NORTHEAST,
REBUILDING ON THE BACK SIDE AND OUTFLOW INTERACTIONS COULD
PROLONG THE STORM THREAT BACK TO NEAR THE US-395 CORRIDOR AND
THE BUG/STALLION FIRES UNTIL ABOUT 6-7 PM.
* WHILE HEAVY RAINFALL (RATES OF 1-2+"/HOUR) CAPABLE OF FLASH
FLOODING AND FREQUENT LIGHTNING ARE THE PRIMARY RISKS, STRONG TO
ISOLATED SEVERE WIND GUSTS AND POTENTIAL FOR ACCUMULATING HAIL
(MAINLY SMALL BUT CAN'T RULE OUT 1" HAIL SIZE EITHER) ARE ALSO
IN THE MIX WITH THESE STORMS.
* LATER THIS EVENING, LEFTOVER SHOWERS WIND DOWN IN WEST CENTRAL
NV WITH THE LOW EXITING TO THE NORTH OF CA/NV. THEN FOR FRIDAY,
A WEAKER TROUGH SHORTWAVE HANGS BACK NEAR THE CA COAST AND
PROVIDES A BIT OF INSTABILITY ALONG WITH RESIDUAL MOISTURE.
WHILE FLOODING RISKS ARE LOWER GIVEN WEAKER FORCING AND
DECREASING PW VALUES COMPARED TO TODAY, ISOLATED PM SHOWERS AND
T-STORMS COULD FORM WITH UP TO 20% CHANCE FOR THE EASTERN SIERRA
AND FAR WESTERN NV, AND ABOUT 30% CHANCE NEAR US-95.
* FOR THE WEEKEND INTO EARLY NEXT WEEK, A QUIETER WEATHER PATTERN
PREVAILS WITH A MODEST SW FLOW OVER THE SIERRA KEEPING MAINLY
DRY AND MILD CONDITIONS, AS TEMPERATURES SETTLE IN THE 80S TO
NEAR 90 DEGREES FOR LOWER ELEVATIONS AND 70S FOR SIERRA
COMMUNITIES. THE NEXT CHANCE FOR SHOWERS AND INCREASED BREEZES
MAY RETURN AROUND THE MIDDLE OF NEXT WEEK, BUT CONFIDENCE IS
LOWER. MJD
AVIATION
* SHOWERS AND T-STORMS INCREASE AFTER 18Z FOR THE EASTERN SIERRA
INCLUDING KMMH, AND AFTER 20Z FOR KRNO-KCXP-KMEV, WITH THE
THREAT (ABOVE 50% CHANCE) CONTINUING THROUGH 01-03Z. THESE
STORMS WILL PRODUCE PERIODS OF MVFR/IFR CONDITIONS WITH HEAVY
RAIN, FREQUENT LIGHTNING, AND ERRATIC GUSTS TO 35 KT. THE TAHOE
AREA TERMINALS (KTVL/KTRK) ARE MORE LIKELY TO BE ON THE WESTERN
FRINGE OF THESE STORMS WITH LESS THAN 20% CHANCE OF DIRECT
IMPACTS BETWEEN 18-22Z, AND DECREASING FURTHER.
* FOR FRIDAY THROUGH THE WEEKEND, VFR CONDITIONS PREVAIL WITH SW-W
GUSTS GENERALLY BELOW 20 KT. ONLY EXCEPTION MAY BE A LINGERING
10-20% CHANCE OF A BRIEF SHOWER OR T-STORM NEAR KRNO-KCXP-KMEV-
KMMH FRIDAY AFTERNOON. MJD
FIRE WEATHER
* WITH IMPROVED HUMIDITY RECOVERY OVER THE TAHOE BASIN AND THE
BEST FORCING ASSOCIATED WITH THE LOW OFF THE CA COAST REMAINING
SOUTH AND WEST OF THE SIERRA CREST, THE RISK FOR DRY LIGHTNING
STRIKES HAS DECREASED. THEREFORE WE HAVE CANCELLED THE FIRE
WEATHER WATCH.
* PRIMARY CONCERNS ARE WITH THUNDERSTORMS TODAY PRODUCING HEAVY
RAINS, STRONG OUTFLOW WINDS. WHILE DRY LIGHTNING POTENTIAL IS
LOW DUE TO THE MUCH HIGHER HUMIDITY WITH SURFACE DEW POINTS IN
THE 40S-50S, A FEW LIGHTNING FIRES COULD IGNITE FROM STRIKES ON
RECEPTIVE VEGETATION OUTSIDE THE RAIN CORES.
* FLOOD WATCH IN EFFECT THROUGH THIS EVENING FOR INCREASED
POTENTIAL OF FLASH FLOODING, MUD SLIDES, AND DEBRIS FLOWS ON
CURRENT AND RECENT BURN AREAS, INCLUDING THE BUG AND STALLION
FIRES JUST NORTH OF RENO. STALLION FIRE PROBABLY SLIGHTLY HIGHER
RISK WITH STEEPER TERRAIN INVOLVED, BUT ANY RAINFALL CAN CREATE
HAZARDOUS CONDITIONS FOR MOVEMENT OF FIRE PERSONNEL. RAINFALL
RATES OVER 1"/HOUR ARE EXPECTED FROM ANY STORMS THIS AFTERNOON.
* OUTFLOW WINDS PRODUCING SUDDEN SHIFTS IN FIRE ACTIVITY AND
DIRECTION ARE ALSO A CONCERN THIS AFTERNOON. LATEST HIGH
RESOLUTION MODELS INDICATE POTENTIAL FOR GUSTS OF 40 MPH CLOSE
TO ACTIVE FIRES, AND OVER 50 MPH FARTHER EAST TOWARD THE US-95
CORRIDOR.
* WHILE SOME DRYING RETURNS THIS WEEKEND, HUMIDITY WON'T DROP NEAR
THE EXTREME DRY LEVELS PRIOR TO THIS STORM EVENT. AFTERNOON
MINIMUMS LOOK TO RANGE FROM 15-25% WITH GOOD TO EXCELLENT
OVERNIGHT RECOVERIES. WINDS WILL BE ON THE LIGHTER SIDE WITH
TYPICAL PM ZEPHYR BREEZES PRODUCING GUSTS 20-25 MPH, BUT NOT
EXPECTING ANY STRONGER WIND PATTERNS INTO EARLY NEXT WEEK. MJD
REV WATCHES/WARNINGS/ADVISORIES
NV...FLOOD WATCH THROUGH THIS EVENING NVZ001-003.
FLOOD WATCH FROM 1 PM PDT THIS AFTERNOON THROUGH THIS EVENING
NVZ004.
CA...FLOOD WATCH THROUGH THIS EVENING CAZ073.
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