110
FXUS65 KREV 092016
AFDREV
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
1216 PM PST SUN NOV 9 2025
KEY MESSAGES
* UNSEASONABLY WARM AND DRY CONDITIONS WITH LIGHT, TERRAIN-DRIVEN
WINDS WILL CONTINUE THROUGH TUESDAY.
* HIGH TEMPERATURES PEAK ON MONDAY WITH A STRONG POSSIBILITY OF
RECORD HIGH TEMPERATURES.
* WE ARE MONITORING A WINTER STORM FOR MID TO LATE WEEK, BUT
MODERATE UNCERTAINTY REMAINS ON ITS TRACK, INTENSITY, AND THE
RESULTING POTENTIAL FOR STRONG WINDS AND SIERRA SNOWFALL.
DISCUSSION
OUR WEEK IS STARTING OFF NICELY, WITH A DOMINANT UPPER LEVEL RIDGE
PROVIDING A MILD AND PARTLY CLOUDY SUNDAY. THIS PLEASANT FALL
PATTERN IS SET TO CONTINUE RIGHT THROUGH VETERANS DAY. THE MAIN
STORY FOR THE FIRST HALF OF THE WEEK WILL BE THE WARMTH, AS THIS
BUILDING RIDGE WILL CAUSE TEMPERATURES TO KEEP CLIMBING, PEAKING ON
MONDAY WITH A STRONG POSSIBILITY OF SETTING NEW HIGH TEMPERATURE
RECORDS. THE EXISTING 74-DEGREE RECORD AT THE RENO-TAHOE
INTERNATIONAL AIRPORT HAS A 70% CHANCE OF BEING BROKEN OUTRIGHT AND
AN 80% CHANCE OF AT LEAST BEING TIED. THIS STABLE AIRMASS WILL ALSO
KEEP WINDS LIGHT AND TERRAIN-DRIVEN AND ALLOW FOR VALLEY INVERSIONS
TO DEVELOP OVERNIGHT.
ALL GOOD THINGS MUST COME TO AN END, AND THIS QUIET PATTERN IS NO
EXCEPTION. A SIGNIFICANT SHIFT IS ON TAP FOR THE MIDDLE OF THE WEEK
AS OUR "BIG BUBBLE, NO TROUBLE" OF HIGH PRESSURE FINALLY ERODES. AN
UPPER-LEVEL TROUGH IS FORECAST TO DIG SOUTHWARD FROM THE GULF OF
ALASKA, APPROACHING THE WEST COAST LATE TUESDAY INTO WEDNESDAY. AS
THIS TROUGH MOVES IN, YOU'LL NOTICE THE CHANGE: SKIES WILL BECOME
MOSTLY CLOUDY ON WEDNESDAY, TEMPERATURES WILL BEGIN A MINOR DROP,
AND BREEZY CONDITIONS WILL PICK UP DURING THE AFTERNOON.
THIS STORM SHOWS THE POTENTIAL FOR STRONG WINDS, WITH THE MAIN EVENT
FOR WINDS CURRENTLY LOOKING TO BE WEDNESDAY NIGHT INTO THURSDAY.
HOWEVER, THE ULTIMATE INTENSITY AND PLACEMENT OF THESE WINDS ARE
HIGHLY CONDITIONAL ON THE FINAL DEPTH AND TRACK OF THE INCOMING
TROUGH. THIS KEY UNCERTAINTY IS WHY THE PLACEMENT OF THE TIGHTENED
PRESSURE GRADIENT KEEPS SHIFTING IN THE MODELS. DYNAMICALLY, THE
INGREDIENTS ARE THERE: ENSEMBLES CONSISTENTLY PLACE A STRONG JET
STREAK OVER THE SIERRA, POSITIONING THE SIERRA FRONT IN THE RIGHT
EXIT REGION OF THE JET, A SPECIFIC AREA THAT IS FAVORABLE FOR
DOWNWARD MOMENTUM TRANSPORT. A DEEPER TROUGH WOULD SUPPORT A
STRONGER JET AND A MORE EFFICIENT TRANSFER OF 50-70 KT 700 HPA
WINDS DOWN TO THE SURFACE. BECAUSE THIS EVOLUTION IS STILL
UNCERTAIN, CURRENT NBM GUIDANCE SHOWS A 40-60% PROBABILITY FOR
WIND GUSTS TO EXCEED 45 MPH LATE WEDNESDAY INTO THURSDAY,
IMPACTING SIERRA VALLEYS, THE SIERRA FRONT, AND PORTIONS OF FAR
WESTERN NEVADA.
ANOTHER BIG UNCERTAINTY WITH THIS TROUGH IS ITS DEPTH - THAT IS, HOW
COLD WILL IT BE? THIS WILL BE THE DECIDING FACTOR FOR SNOW LEVELS
AND POTENTIAL ACCUMULATIONS. ENSEMBLES CONTINUE TO WAVER ON THIS,
AND AS IT STANDS, THE POTENTIAL SNOW LEVEL FOR DONNER SUMMIT HAS A
PRETTY BIG RANGE FROM AS LOW AS 3000 FEET TO AS HIGH AS 7000 FEET.
THIS IS THE KEY DETAIL WE WILL BE REFINING IN THE COMING DAYS. WE
ARE ALSO TRACKING A HEALTHY PLUME OF MOISTURE, WHICH IS CONSISTENTLY
FORECAST TO BE AIMED AT THE SIERRA. THE ORIENTATION OF THIS PLUME
SUGGESTS THAT THE HEAVIEST PRECIPITATION WILL LIKELY FALL WEST AND
ALONG THE SIERRA CREST, WITH MODEST SPILLOVER INTO WESTERN NEVADA.
WHILE IT IS 3+ DAYS OUT AND THESE DETAILS WILL CHANGE, THE CURRENT
PROBABILISTIC OUTLOOK FOR THE MAIN STORM PERIOD (WEDNESDAY EVENING
THROUGH FRIDAY) GIVES US A FIRST LOOK AT POTENTIAL TOTALS. FOR
SIERRA PASSES LIKE DONNER AND ECHO SUMMITS, THERE IS AN 80-85%
CHANCE OF OVER 1 INCH OF RAIN, A 60-65% CHANCE OF OVER 2 INCHES, AND
A 25-30% CHANCE OF OVER 3 INCHES. FOR SNOWFALL IN THOSE SAME
LOCATIONS, THERE IS A 65-75% CHANCE OF OVER 6 INCHES, A 35-55%
CHANCE OF OVER A FOOT, AND A 10-20% CHANCE OF OVER 18 INCHES. FOR
WESTERN NEVADA CITIES LIKE RENO AND CARSON CITY, THE PROBABILITIES
FOR RAINFALL ARE 50-70% FOR OVER 0.50 INCHES, 30-55% FOR OVER 0.75
INCHES, AND A 15-35% PROBABILITY OF OVER AN INCH.
THE CONSISTENT SIGNAL FOR A PATTERN CHANGE IS CLEAR, AND THOSE IN
THE REGION SHOULD USE THE CALM FIRST HALF OF THE WEEK TO PREPARE FOR
POTENTIAL IMPACTS FROM STRONG WINDS, VALLEY RAIN, AND SIERRA SNOW
LATE WEDNESDAY THROUGH FRIDAY.
-JOHNSTON
AVIATION
VFR CONDITIONS WILL PREVAIL ACROSS ALL TERMINALS TODAY AND MONDAY
UNDER LIGHT, TERRAIN-DRIVEN SURFACE WINDS AND SCATTERED CIRRUS.
THE MAIN EXCEPTION WILL BE AT KTRK TONIGHT INTO MONDAY MORNING.
WHILE A STRONG INVERSION WILL BE IN PLACE, DEW POINT DEPRESSIONS ARE
FORECAST TO REMAIN AROUND 2-4 DEGREES OVERNIGHT, WHICH IS TYPICALLY
UNFAVORABLE FOR WIDESPREAD FZFG (15% PROBABILITY), BUT SOME PATCHY
FZFG OR BR ARE POSSIBLE. THIS MAY CAUSE BRIEF MVFR TO IFR CONDITIONS
FROM 06Z-16Z MONDAY.
AVIATORS SHOULD ENJOY THESE QUIET VFR CONDITIONS, AS A PATTERN
CHANGE IS FORECAST TO BRING STRONGER WINDS AND PRECIPITATION TO THE
REGION MID-TO-LATE WEEK.
-JOHNSTON
REV WATCHES/WARNINGS/ADVISORIES
NV...NONE.
CA...NONE.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page