236
FXUS65 KREV 170903
AFDREV
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
203 AM PDT WED SEP 17 2025
KEY MESSAGES
* WARM, SUNNY, AND DRY WEATHER CONTINUES THROUGH TODAY, WITH
SEVERAL DEGREES OF COOLING LATER THIS WEEK.
* HAZE AND PATCHY SMOKE FROM THE GARNET FIRE WILL LINGER THIS
MORNING IN SOUTHERN MONO COUNTY, WITH IMPROVEMENT LATER TODAY.
* SHOWERS AND THUNDERSTORMS RETURN LATE THURSDAY WITH THE HIGHEST
OVERALL CHANCES ON FRIDAY, AND LINGERING SHOWERS POSSIBLE INTO
THE WEEKEND.
DISCUSSION
ANOTHER WARM AND DRY DAY WILL PREVAIL TODAY WITH HIGHS PEAKING IN
THE UPPER 80S-NEAR 90 FOR LOWER ELEVATIONS AND EDGING ABOVE 80
DEGREES FOR SIERRA COMMUNITIES. LINGERING SMOKE AND HAZE FROM THE
GARNET FIRE IS CURRENTLY PRODUCING AIR QUALITY REDUCTIONS TO
MODERATE AND ISOLATED UNHEALTHY FOR SENSITIVE GROUPS CATEGORIES
IN SOUTHERN MONO COUNTY. THESE CONDITIONS ARE PROJECTED TO LINGER
THROUGH THIS MORNING, FOLLOWED BY IMPROVING CONDITIONS THIS
AFTERNOON. INCREASING CIRRUS COVERAGE FROM THE SOUTH THIS
AFTERNOON WILL SIGNIFY A CHANGE IN THE WEATHER PATTERN FOR
THURSDAY-FRIDAY WITH A COOLING TREND AND INCREASED CHANCES FOR
SHOWERS/ISOLATED THUNDERSTORMS.
HOWEVER, SEVERAL MOVING PARTS NEAR AND OFF THE CA COAST ARE
LEADING TO A VARIETY OF SCENARIOS THAT WILL IMPACT THE AMOUNTS,
EXTENT AND LOCATION OF THE TOTAL RAINFALL. REMNANT MOISTURE FROM
FORMER TROPICAL STORM MARIO AND A SEPARATE UPPER LOW OFF THE
SOUTHERN CA COAST ARE THE MAIN CONTRIBUTORS TO THE. THE MORE
AGGRESSIVE SCENARIOS COMBINE THE INCREASED FORCING FROM THE LOW
MOVING INLAND TO CENTRAL CA AND MARIO'S DEEP MOISTURE WHICH COULD
LEAD TO BANDS OF HEAVIER RAIN SHOWERS/EMBEDDED T-STORMS,
ESPECIALLY FOR THE EASTERN SIERRA AND WESTERN NV SOUTH OF US-50,
WITH DECREASING POTENTIAL FARTHER NORTH. ON THE FLIP SIDE, OTHER
SCENARIOS DIVERT THE MAJORITY OF THE TROPICAL MOISTURE INTO THE
SOUTHWEST US WHILE THE UPPER LOW REMAINS OFFSHORE FROM THE CA
COAST. THE RESULT OF THIS OUTCOME WOULD STILL BE PLENTY OF MID-
UPPER LEVEL CLOUDS, BUT ONLY SPOTTY LIGHT RAINFALL.
HIGHER RESOLUTION GUIDANCE IS ONLY STARTING TO REACH THIS TIME
FRAME, WITH THICKER CLOUDS ADVANCING FROM SOUTH TO NORTH THURSDAY,
AND INITIAL SHOWER FORMATION ACROSS THE EASTERN SIERRA THURSDAY
AFTERNOON. ADDITIONAL SHOWER ACTIVITY SPREADS NORTHWARD ACROSS
EASTERN CA-WESTERN NV THURSDAY NIGHT WITH THE BEST CHANCES FROM
US-50 SOUTHWARD, BUT ISOLATED ACTIVITY MAY EXTEND FARTHER NORTH
ACROSS THE REGION OVERNIGHT INTO FRIDAY MORNING.
FRIDAY IS THE DAY TO WATCH FOR POSSIBLE THUNDERSTORMS AND HEAVIER
RAINFALL, BUT ONLY IF THE UPPER LEVEL FORCING SETS UP IN THE
FAVORED LOCATION NEAR OR EAST OF THE SIERRA, AND ENOUGH CLEARING
OR THINNING OF CLOUDS OCCURS TO ALLOW STORMS TO FORM. IF PLANNING
OUTDOOR ACTIVITIES ESPECIALLY ON FRIDAY, KEEP POSTED TO THE LATEST
FORECAST UPDATES AND DISCUSSIONS, AND CONSIDER ALTERNATE OPTIONS
IF UPCOMING TRENDS FAVOR THE WETTER/STORMY SCENARIOS.
AS WE GET TO THE WEEKEND AND EARLY NEXT WEEK, MOST OF THE GUIDANCE
SHOWS AN OVERALL DRIER TREND WITH TEMPERATURES REBOUNDING INTO THE
80S FOR LOWER ELEVATIONS AND MID-UPPER 70S NEAR THE SIERRA. HOWEVER,
ISOLATED SHOWERS CAN'T BE RULED OUT EACH AFTERNOON ESPECIALLY IF
RAIN FROM THURSDAY-FRIDAY LEAVES BEHIND LINGERING MOISTURE WITH
INCREASED DAYTIME HEATING.
THE NEXT INCREASE IN RAIN CHANCES WITH A COOLING TREND MAY RETURN
BY NEXT TUESDAY-WEDNESDAY WITH ANOTHER POTENTIAL APPROACH OF A
CLOSED UPPER LOW, BUT AT THIS TIME CONFIDENCE IS LOWER DUE TO WIDE
VARIANCE OF TRACKS AMONG THE MEDIUM RANGE ENSEMBLE GUIDANCE FOR
THIS SYSTEM. THE ONLY CERTAINTY FOR NEXT WEEK IS OFFICIALLY
ENTERING THE FALL SEASON AFTER EQUINOX OCCURS NEXT MONDAY AT
11:19 AM PDT. MJD
AVIATION
VFR CONDITIONS WITH GENERALLY LIGHT NE-E FLOW WILL PERSIST FOR
ALL WESTERN NEVADA AND SIERRA TERMINALS THROUGH THIS AFTERNOON.
LINGERING HAZE DUE TO SMOKE FROM THE GARNET FIRE MAY REDUCE
SLANTWISE VISIBILITY AROUND KMMH THIS MORNING THRU 18Z.
IMPROVEMENT IS EXPECTED THIS AFTERNOON AS SMOKE TRAJECTORY
GUIDANCE HOLDS TODAY'S SMOKE PLUMES CLOSER TO THE FIRE SITE AND
AWAY FROM MONO COUNTY.
CIRRUS CLOUD COVER WILL INCREASE AND EXPAND NORTHWARD THIS
AFTERNOON AND TONIGHT, WITH THICKER MID-HIGH LEVEL CLOUD COVER
ARRIVING ON THURSDAY. ISOLATED RAIN SHOWER CHANCES MAY ARRIVE TO
KMMH AFTER 21Z THURSDAY AND EXPAND NORTHWARD TO THE OTHER MAIN
TERMINALS AROUND TAHOE AND FAR WESTERN NV THURSDAY NIGHT. MJD
REV WATCHES/WARNINGS/ADVISORIES
NV...NONE.
CA...NONE.
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