109
FXUS66 KHNX 190455
AFDHNX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HANFORD CA
955 PM PDT SUN OCT 18 2026
KEY MESSAGES
1. SEASONALLY AVERAGE CONDITIONS MONDAY
2. HIGH CONFIDENCE IN A PATTERN CHANGE STARTING TUESDAY.
3. TEMPERATURES WELL BELOW AVERAGE NEXT WEEK WITH MODERATE
CONFIDENCE OF RAIN AND HIGH SIERRA SNOW EARLY WEDNESDAY MORNING
THROUGH THURSDAY.
DISCUSSION
SUNDAY, OCTOBER 18 IS STILL ON TRACK TO BE THE LAST DAY OF 90
DEGREE TEMPERATURE IN 2026. IN ANTICIPATION OF A MAJOR PATTERN
CHANGE LATER THIS WEEK, HIGH TEMPERATURES MONDAY ARE EXPECTED
IN THE LOW-TO-MID 80S ACROSS THE SAN JOAQUIN VALLEY AND MOJAVE
DESERT. MINIMUM RELATIVE HUMIDITY WILL LIKEWISE IMPROVE, WITH
ALL AREAS OUTSIDE THE DESERT EXPECTED ABOVE 20 PERCENT.
HOPEFULLY, THIS INDICATES THE REST OF 2026 IS ALSO FREE OF LARGE
FIRE CONCERNS.
NOW FOR THE EXCITING PART OF THE DISCUSSION: RAIN AND SNOW.
ENSEMBLE MODELS ARE IN GOOD AGREEMENT A CLOSED LOW APPROACHES
FROM THE PACIFIC NORTHWEST ON TUESDAY, THEN SLOWLY TRAVERSES
CALIFORNIA WEST TO EAST ON WEDNESDAY. AS THIS LOW WILL BE
APPROACHING FROM CONTINENTAL AREAS RATHER THAN THE PACIFIC
OCEANS, TEMPERATURES IN MUCH OF THE FORECAST AREA WILL STRUGGLE
TO REACH 75 DEGREES AND HIGHER, WITH A LESS THAN 10 PERCENT
CHANCE BY THURSDAY ACROSS THE MOJAVE DESERT AND SAN JOAQUIN
VALLEY.
PRECIPITATION CHANCES FIRST ENTER THE FORECAST ALONG THE SIERRA
NEVADA ON TUESDAY MORNING, BEFORE SPREADING REGION-WIDE AND
PEAKING WEDNESDAY MORNING. THE ENTIRE AREA HAS A 70-90% CHANCE
TO SEE AT LEAST A TRACE OF RAIN ON WEDNESDAY, WITH CHANCES FOR A
TENTH OF AN INCH OR MAIN RANGING FROM 40-50% IN THE MOJAVE
DESERT, 50-70% IN THE SAN JOAQUIN VALLEY, AND 80-90% IN THE
SIERRA NEVADA. THESE CHANCES TAKE A 5-10% HIT ON THURSDAY,
BEFORE SIGNIFICANTLY DECREASING BY FRIDAY.
AS THIS UPCOMING CLOSED-LOW IS ON TRACK TO BE THE FIRST
MEANINGFUL EVENT OF WATER YEAR 2027 (AND CLOSED LOWS BRING
FORECASTER WOES), A FEW SORE-SPOTS ARE POSSIBLE. FIRSTLY, SOME
ENSEMBLE MODEL MEMBERS ARE SIGNALING ELEVATED WIND GUSTS ALONG
TEJON PASS, WHERE THE NATIONAL BLEND OF MODELS (NBM) INDICATES A
30-40% CHANCE FOR MAXIMUM WIND GUSTS ABOVE 40 MPH. IF THIS
COMES TO FRUITION, SLICK ROADS AND GUSTY WINDS WILL MAKE TRAVEL
ALONG THE GRAPEVINE DIFFICULT. SECONDLY, THE WEATHER PREDICTION
CENTER INDICATES A MARGINAL (5 PERCENT CHANCE) FOR EXCESSIVE
RAINFALL WEDNESDAY AND THURSDAY, AS A FEW ENSEMBLE MEMBERS PLACE
AS MUCH AS AN INCH OF RAIN ACROSS THE ENTIRE FORECAST AREA ON
WEDNESDAY AND THURSDAY. BECAUSE OF THIS, WE HAVE SOME CONCERN
FOR FLASH FLOODING IN POORLY-DRAINING HYDROPHOBIC AREAS,
INCLUDING THE MOJAVE DESERT AND TEHACHAPI PASS.
THE LAST SORE-SPOT? SNOW! MODEL RUNS THIS WEEKEND HAVE STEADILY
INCREASED THE SNOW LEVEL CLOSER TO 8,000 FEET. SEMANTICS ASIDE,
THERE IS HIGH CONFIDENCE (GREATER THAN 80 PERCENT) FOR AT LEAST
AN INCH OF SNOW TO ACCUMULATE ON WEDNESDAY INTO THURSDAY.
SCENARIO-WISE, A WORST-CASE, 10% CHANCE OF OCCURRENCE SCENARIO
PLACES 6-10 INCHES OF SNOW ABOVE 8,000 FEET. WHICHEVER ENDS UP
THE WINNER, TRAVEL WILL ALSO BE DIFFICULT ACROSS SIERRA NEVADA
PASSES IN REDUCED VISIBILITY AND SLICK ROADS AS WELL.
AVIATION
VFR CONDITIONS AND LIGHT WINDS WILL PREVAIL FOR THE NEXT 24
HOURS.
AIR QUALITY ISSUES
NONE
CERTAINTY
THE LEVEL OF CERTAINTY FOR DAYS 1 AND 2 IS HIGH.
THE LEVEL OF CERTAINTY FOR DAYS 3 THROUGH 7 IS MEDIUM.
CERTAINTY LEVELS INCLUDE LOW...MEDIUM...AND HIGH. PLEASE VISIT
WWW.WEATHER.GOV/HNX/CERTAINTY.HTML FOR ADDITIONAL INFORMATION
AND/OR TO PROVIDE FEEDBACK.
HNX WATCHES/WARNINGS/ADVISORIES
NONE.
PUBLIC/AVIATION...ND
WEATHER.GOV/HANFORD
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