206
FXUS66 KSTO 162059
AFDSTO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
1259 PM PST SAT NOV 16 2024
SYNOPSIS
A QUICK MOVING SYSTEM TRAVERSES INTERIOR NORCAL LATE SUNDAY INTO
MONDAY BRINGING LIGHT PRECIPITATION AND BREEZY TO LOCALLY GUSTY
SOUTH TO WEST WINDS. COLD OVERNIGHT/MORNING TEMPERATURES ARE THEN
EXPECTED TO CONTINUE THROUGH TUESDAY. UNSETTLED WEATHER LOOKS TO
PERSIST MID TO LATE WEEK, PARTICULARLY NORTH OF INTERSTATE 80,
WITH MORE WIDESPREAD PRECIPITATION POTENTIAL BY NEXT WEEKEND.
DISCUSSION
AS OF EARLY THIS AFTERNOON, ASIDE FROM SOME HIGH CIRRUS CLOUDS
SPREADING SOUTHWARD, MOSTLY SUNNY SKIES ARE EVIDENT VIA LATEST
GOES- WEST SATELLITE IMAGERY. DESPITE THE MOSTLY ABUNDANT
SUNSHINE, TEMPERATURES ACROSS THE REGION ARE TRENDING SLIGHTLY
BELOW NORMAL AT THIS TIME, WITH HIGH TEMPERATURES BEFORE THE END
OF THE DAY LOOKING TO REACH THE 50S TO LOW 60S. BREEZY NORTH-
NORTHWEST WINDS ARE EXPECTED TO GRADUALLY SUBSIDE THIS AFTERNOON
AND EVENING AS UPPER LEVEL TROUGHING CONTINUES TO DIG
SOUTHWESTWARD AND RIDGING ALOFT BUILDS IN BEHIND IT. THIS WILL
LEAD TO ANOTHER NIGHT/MORNING OF COLD, BELOW NORMAL TEMPERATURES
IN THE UPPER 30S TO LOW 40S IN THE VALLEY/FOOTHILLS FOR MUCH OF
INTERIOR NORCAL ALONGSIDE SOME PATCHY FROST POTENTIAL.
FOLLOWING THE COLD START ON SUNDAY MORNING, HIGH TEMPERATURES ARE
EXPECTED TO REBOUND TO SIMILAR VALUES AS TODAY. THE
AFOREMENTIONED BUILDING RIDGE IS THEN EXPECTED TO BECOME RAPIDLY
REPLACED BY A SHORTWAVE DIGGING SOUTHWESTWARD FROM THE GULF OF
ALASKA THROUGHOUT THE DAY ON SUNDAY. THIS WILL RESULT IN SOUTH TO
WEST WINDS BECOMING BREEZY TO LOCALLY GUSTY (STRONGEST GUSTS 40-50
MPH EXPECTED ALONG THE SIERRA, GUSTS 15 TO 25 MPH ELSEWHERE) FROM
SUNDAY AFTERNOON THROUGH EARLY MONDAY MORNING. ADDITIONALLY, THIS
QUICK MOVING WAVE IS EXPECTED TO BRING SOME LIGHT PRECIPITATION
TO INTERIOR NORCAL SUNDAY AFTERNOON INTO MONDAY MORNING, ALTHOUGH
MOST ACCUMULATING PRECIPITATION LOOKS TO OCCUR ALONG THE SIERRA
AND INTO THE NORTHERN SACRAMENTO VALLEY. CURRENT PROBABILITIES OF
PRECIPITATION EXCEEDING 0.25" ARE AROUND 40% TO 60% FOR THESE
AREAS. GIVEN SNOW LEVELS BEGINNING AROUND 6000 TO 7000 FEET FOR
MUCH OF THE EVENT (ALTHOUGH RAPIDLY DROPPING TO 3000 TO 4000 FEET
BY MONDAY MORNING) CORRESPONDING PROBABILITIES OF SNOWFALL
EXCEEDING 4" SIT AROUND 30% TO 60% FOR ELEVATIONS ABOVE 6500 FEET.
AS THIS IS EXPECTED TO BE A FAIRLY TRANSIENT SYSTEM,
PRECIPITATION IMPACTS LOOK TO TAPER OFF THROUGH MONDAY MORNING,
WITH DRIER WEATHER THEN THROUGH THE MAJORITY OF MONDAY INTO
TUESDAY. BREEZY NORTHERLY WINDS ARE ANTICIPATED IN THE WAKE OF
THIS SYSTEM THOUGH, WHICH WILL WORK TO BRING COOLER TEMPERATURES
TO THE REGION, ESPECIALLY INTO TUESDAY MORNING. AS WINDS LESSEN
INTO THE OVERNIGHT PERIOD AND SKIES CLEAR AS THE SYSTEM DEPARTS TO
THE EAST, APPRECIABLE RADIATIONAL COOLING CONDITIONS ARE LOOKING
LIKELY. RESULTANT PROBABILITIES OF TUESDAY MORNING LOW
TEMPERATURES LESS THAN 36F ARE CURRENTLY AROUND 40% TO 80% FOR
MOST VALLEY AND FOOTHILLS LOCATIONS. AT LEAST PATCHY FROST IS
EXPECTED, WITH SOME POTENTIAL FOR MORE WIDESPREAD FROST
DEVELOPMENT IF IDEAL RADIATIONAL COOLING IS REALIZED.
EXTENDED DISCUSSION (WEDNESDAY THROUGH SATURDAY)
WHILE THE AFOREMENTIONED EARLY WEEK SHORTWAVE IS EXPECTED TO
EJECT EASTWARD, A SEPARATE GULF OF ALASKA TROUGH LOOKS TO DIG
SOUTHWESTWARD OVER THE PACIFIC OCEAN AS RIDGING BUILDS THROUGH THE
INTERMOUNTAIN WEST. THIS GENERAL PATTERN WILL SETUP LARGE SCALE
ZONAL FLOW ALOFT ACROSS NORCAL FROM MID TO LATE WEEK. THERE ARE
SOME DISCREPANCIES REGARDING THE EVENTUAL TIMING AND PROGRESSION
OF THIS BUILDING TROUGH. HOWEVER, GIVEN THE FAVORABLE FETCH FOR
MOISTURE ADVECTION AND RELATIVE PROXIMITY OF THE SYSTEM TO NORCAL,
SOME MINOR PRECIPITATION IMPACTS WILL BE POSSIBLE FROM WEDNESDAY
THROUGH FRIDAY, PARTICULARLY ACROSS THE NORTHERN/CENTRAL
SACRAMENTO VALLEY AND ADJACENT TERRAIN (GENERALLY FROM INTERSTATE
80 NORTHWARD). RESULTANT PROBABILITIES OF PRECIPITATION EXCEEDING
1" FROM WEDNESDAY THROUGH FRIDAY ARE CURRENTLY AROUND 40% TO 70%
FOR THESE AREAS, WITH ONLY 20% TO 40% PROBABILITIES OF EXCEEDING
0.25" OF PRECIPITATION FROM INTERSTATE 80 SOUTHWARD. TEMPERATURES
ARE OTHERWISE EXPECTED TO TREND CLOSER TO SEASONAL NORMALS THROUGH
THE END OF THE WEEK. ALTHOUGH THERE IS A HIGH DEGREE OF
UNCERTAINTY REGARDING THE EVENTUAL TRACK AND TIMING OF THE TROUGH
PROGRESSION, THE MAJORITY OF ENSEMBLE GUIDANCE DOES INDICATE THE
SYSTEM MOVING ONSHORE AT SOME POINT NEXT WEEKEND. WHILE THIS WOULD
LIKELY RESULT IN MORE WIDESPREAD PRECIPITATION IMPACTS, THERE IS
DECIDEDLY LOW CONFIDENCE IN THE EXACT DEGREE OF THOSE IMPACTS AT
THIS TIME.
AVIATION
VFR CONDITIONS ACROSS INTERIOR NORTHERN CALIFORNIA OVER THE NEXT
24 HRS. SFC NORTH WINDS IN THE CENTRAL VALLEY WITH GUSTS UP TO 15
KTS UNTIL 00Z SUN, MOSTLY ACROSS THE DELTA AREA, BEFORE TAPERING
OFF THROUGH THE EVENING.
STO WATCHES/WARNINGS/ADVISORIES
NONE.
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