984
FXUS66 KSTO 181111
AFDSTO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
311 AM PST WED DEC 18 2024
SYNOPSIS
DRY WEATHER AND FOGGY MORNINGS ARE EXPECTED THROUGH THE REMAINDER
OF THE WEEK. AN UNSETTLED WEATHER PATTERN IS THEN FORECAST FOR
THE WEEKEND AND INTO THE HOLIDAY WEEK.
DISCUSSION
UPPER LEVEL RIDGING CONTINUES OVER THE AREA WITH SOME LIGHT
NORTHERLY WINDS THIS MORNING OVER THE NORTHERN SACRAMENTO VALLEY,
WITH GENERALLY LIGHT SOUTHEASTERLY WINDS ELSEWHERE. IR SATELLITE
SHOWS AN AREA OF PATCHY FOG/MIST AND LOW CLOUDS MOVING NORTHERLY
UP THROUGH THE NORTHERN SAN JOAQUIN VALLEY INTO THE SACRAMENTO
VALLEY AND DELTA, REACHING OROVILLE. THE NORTHERLY WINDS SHOULD
SLOW THIS PROGRESSION FURTHER NORTH. THE ADVECTION OF LOW STRATUS
CLOUDS FROM THE SOUTH MAY ACT TO LIMIT THE DEVELOPMENT OF
WIDESPREAD DENSE FOG TO SOME EXTENT, BUT AT LEAST PATCHY FOG IS
EXPECTED TO CONTINUE THROUGH THE MORNING. THE LATEST HREF SHOWS A
MORE NORTHERLY ORIENTED AREA OF FOG FOR THIS MORNING, WITH AN 80%
PROBABILITY OF VISIBILITY LESS THAN A HALF MILE FROM THE SACRAMENTO
AREA NORTH TO AROUND OROVILLE. WILL CLOSELY MONITOR THIS TO SEE
HOW THIS FOG DEVELOPS. FOG THAT DEVELOPS COULD LIFT AGAIN INTO
LOW STRATUS CLOUDS AND LINGER THIS AFTERNOON OVER THE VALLEY AND
DELTA, LIMITING DAYTIME HEATING AGAIN, WITH HIGH TEMPERATURES
CLOSER TO THE MID TO UPPER 50S WHERE STRATUS LINGERS. THE
EXCEPTION WILL LIKELY BE THE NORTHERN SACRAMENTO VALLEY, WHICH
SHOULD SEE MORE SUN AT HIGHS IN THE LOW TO MID 60S. HIGH
TEMPERATURES IN THE UPPER 50S TO LOW 60S ARE ANTICIPATED IN THE
FOOTHILLS AND LOWER MOUNTAINS, WITH 40S TO LOW 50S AT HIGHER
ELEVATIONS.
FOG POTENTIAL RETURNS AGAIN LATE TONIGHT INTO THURSDAY
MORNING, POTENTIALLY SPREADING ALL THE WAY NORTH IN THE VALLEY TO
REDDING. HREF PROBABILITIES OF VISIBILITY LESS THAN 0.5 MILES IN
THESE AREAS SIT AROUND 40% TO 75% FOR THURSDAY MORNING, HIGHEST
FROM I-80 NORTHWARD. HIGH TEMPERATURES LOOK TO WARM SLIGHTLY,
COMPARED TO WEDNESDAY, SLIGHTLY ABOVE NORMAL LEVELS FOR THIS TIME
OF YEAR. THE FOG POTENTIAL WILL BE MORE LIMITED FRIDAY, WITH
INCREASED HIGH CLOUD COVER AND A LITTLE MORE WIND AHEAD OF A WEAK
SYSTEM TO THE NORTHWEST. THERE IS A SLIGHT CHANCE OF
PRECIPITATION FRIDAY NIGHT AS A MORE SUBSTANTIAL, QUICK MOVING
SYSTEM APPROACHES. WIDESPREAD MODERATE RAIN AND HIGH MOUNTAIN SNOW
ARE EXPECTED SATURDAY. SNOW LEVELS WILL BE RATHER HIGH, 6500 TO
7500 FEET, WHICH WILL LIMIT IMPACTS TO TRAVEL. WET SNOW
ACCUMULATIONS OF AROUND 1 TO 3 INCHES ARE CURRENTLY PROJECTED BY
THE NBM THROUGH SATURDAY NIGHT AROUND SIERRA PASS LEVELS, WHICH
COULD CAUSE BRIEF MOUNTAIN TRAVEL DELAYS. THE NBM SHOWS A 40 TO
75% PROBABILITY OF 1 INCH OR MORE OF RAIN FOR THE NORTHERN
SACRAMENTO VALLEY, ADJACENT FOOTHILLS, AND NORTHERN
SIERRA/SOUTHERN CASCADES. THE SACRAMENTO VALLEY WILL SEE A 40 TO
70% PROBABILITY OF 0.5 INCHES OR MORE, WHILE THE NORTHERN SAN
JOAQUIN VALLEY WILL ONLY SEE AROUND 10% CHANCE.
IN ADDITION TO PRECIPITATION, THIS SYSTEM WILL BRING GUSTY
SOUTHERLY WINDS, WITH GUSTS TO 20 TO 30 MPH ON SATURDAY,
STRONGEST FOR LOWER ELEVATIONS OVER THE EASTERN SIDE OF THE
SACRAMENTO VALLEY. THE MOUNTAINS COULD SEE GUSTS TO 40 MPH.
EXTENDED DISCUSSION (SUNDAY THROUGH WEDNESDAY)
ENSEMBLES AND CLUSTERS CONTINUE TO SHOW A WET, UNSETTLED PATTERN
FOR NEXT WEEK AS A SERIES OF WAVES MOVE THROUGH. THE FIRST OF
THESE WAVES EXITS EARLY SUNDAY WITH SOME SHOWERS LINGERING.
ANOTHER WAVE CLOSELY FOLLOWS, BRINGING CHANCES OF SHOWERS ACROSS
THE AREA DURING THE DAY AND THEN LIKELY PRECIPITATION SUNDAY
EVENING INTO MONDAY. THIS IS EXPECTED TO BE AN EVEN WARMER SYSTEM,
WITH SNOW LEVELS GENERALLY STAYING ABOVE 6500 TO 7000 FEET DURING
THE DAY, 7000 TO 8000 FEET SUNDAY NIGHT. THIS MEANS THE MAJORITY
OF PRECIPITATION WILL FALL AS RAIN, WITH SNOW LIMITED TO HIGH
PEAKS. CURRENT FORECAST RAIN AMOUNTS THROUGH THE WEEKEND HAVE
TRENDED DOWN SOMEWHAT, WITH HIGHEST TOTALS AROUND 2.50 INCHES OVER
THE MOUNTAINS OF SHASTA COUNTY, AROUND AN 1.50 INCHES FOR THE
SIERRA. VALLEY WEEKEND TOTALS RANGE FROM 0.10 INCH OVER THE
NORTHERN SAN JOAQUIN VALLEY TO UP TO 1.25 INCHES FOR REDDING.
CONFIDENCE CONTINUES TO INCREASE THE UNSETTLED WEATHER CONTINUING
THROUGH THE MIDDLE OF NEXT WEEK. WHILE DETAILS ARE UNCERTAIN, IT
CURRENTLY LOOKS LIKE MOST OF THE DAY MONDAY WILL SEE A LULL IN
PRECIPITATION, WITH STRONGER SYSTEM MOVING IN BY LATE IN THE
EVENING. THIS WILL BRING RENEWED PRECIPITATION CHANCES TUESDAY AND
FURTHER INTO THE HOLIDAY WEEK. SNOW LEVELS ON MONDAY AND EARLY
TUESDAY (CHRISTMAS EVE) REMAIN ABOVE PASS LEVEL, THOUGH BY
TUESDAY AFTERNOON IT LOOKS LIKE THIS DROP AS COLDER AIR MOVES INTO
THE AREA. THIS COULD BRING IMPACTFUL SNOW LATER IN THE DAY AND
NIGHT, POTENTIALLY IMPACTING HOLIDAY TRAVEL. CONTINUE TO CHECK
BACK IN FOR UPDATES AS DETAILS COME BETTER INTO FOCUS!
AVIATION
PERIODS OF MVFR/IFR WITH LIFR CONDITIONS WITH BR/FG CONDITIONS
CONTINUING THROUGH AROUND 21Z IN THE VALLEY. HREF PROBABILITIES OF
SURFACE VISIBILITIES LESS THAN 1/2SM AROUND 40-80% FROM CHICO TO
MODESTO, AND IN THE DELTA. BR/FG MAY LIFT INTO A LOW STRATUS DECK
BEYOND 21Z, MAINLY IN THE CENTRAL/SOUTHERN SACRAMENTO VALLEY AND
NORTHERN SAN JOAQUIN VALLEY. SURFACE WINDS GENERALLY BELOW 12
KNOTS, WITH DIURNAL WIND PATTERN TAKING OVER. WINDS GUSTING TO 20
KNOTS IN THE HIGHER SIERRA ELEVATIONS.
STO WATCHES/WARNINGS/ADVISORIES
NONE.
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