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FXUS66 KSTO [Sacramento/WFO CA] 222203 AFDSTO 

FXUS66 KSTO 222203
AFDSTO [HEAD]

National Weather Service Sacramento California 3:03pm PDT Wed May 22 2019 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
303 PM PDT WED MAY 22 2019 [HEAD]

Synopsis. Generally light Sierra showers and isolated afternoon thunderstorms next couple of days as an upper low liners over the Great Basin. Mainly dry elsewhere next couple of days with near normal temperatures. Showers and isolated thunderstorms Friday through Memorial Day as another low drops out of western Canada. 

.SYNOPSIS...
GENERALLY LIGHT SIERRA SHOWERS AND ISOLATED AFTERNOON THUNDERSTORMS
NEXT COUPLE OF DAYS AS AN UPPER LOW LINERS OVER THE GREAT BASIN.
MAINLY DRY ELSEWHERE NEXT COUPLE OF DAYS WITH NEAR NORMAL
TEMPERATURES. SHOWERS AND ISOLATED THUNDERSTORMS FRIDAY THROUGH
MEMORIAL DAY AS ANOTHER LOW DROPS OUT OF WESTERN CANADA. [DISC]

Discussion. The upper level low which brought snow and thunderstorms yesterday is currently centered over Southern California. Mostly sunny skies with some high and mid clouds are present across most of the area. Temperatures are 5–18° warmer than yesterday, though will remain below normal for this time of year. Isolated light showers are starting to develop over the Sierra and foothills. There could be enough instability for a few afternoon/evening thunderstorms to form over the mountains and foothills. 

.DISCUSSION...
THE UPPER LEVEL LOW WHICH BROUGHT SNOW AND THUNDERSTORMS YESTERDAY
IS CURRENTLY CENTERED OVER SOUTHERN CALIFORNIA. MOSTLY SUNNY
SKIES WITH SOME HIGH AND MID CLOUDS ARE PRESENT ACROSS MOST OF THE
AREA. TEMPERATURES ARE 5 TO 18 DEGREES WARMER THAN YESTERDAY,
THOUGH WILL REMAIN BELOW NORMAL FOR THIS TIME OF YEAR. ISOLATED
LIGHT SHOWERS ARE STARTING TO DEVELOP OVER THE SIERRA AND
FOOTHILLS. THERE COULD BE ENOUGH INSTABILITY FOR A FEW
AFTERNOON/EVENING THUNDERSTORMS TO FORM OVER THE MOUNTAINS AND
FOOTHILLS. [DISC]

Upper troughing over the Great Basin with northeasterly flow will continue the shower and thunderstorm threat over the Sierra Cascade Range and foothills on Thursday. The airmass warms slightly so should see a little warm up to slightly below normal high temperatures for this time of year. Breezy northerly winds are expected during the day, gusting up to 20–30 mph over the northern and central Sacramento Valley. 

UPPER TROUGHING OVER THE GREAT BASIN WITH NORTHEASTERLY FLOW WILL
CONTINUE THE SHOWER AND THUNDERSTORM THREAT OVER THE SIERRA
CASCADE RANGE AND FOOTHILLS ON THURSDAY. THE AIRMASS WARMS
SLIGHTLY SO SHOULD SEE A LITTLE WARM UP TO SLIGHTLY BELOW NORMAL
HIGH TEMPERATURES FOR THIS TIME OF YEAR. BREEZY NORTHERLY WINDS
ARE EXPECTED DURING THE DAY, GUSTING UP TO 20 TO 30 MPH OVER THE
NORTHERN AND CENTRAL SACRAMENTO VALLEY. [DISC]

Another upper low drops southward out of western Canada Thursday night will nudge the Great Basin low eastward bringing a temporary dry period Thursday night and Friday morning. This break will be short lived however with the upper low approaching Northern California with a threat of showers or thunderstorms for the mountains and the northern Sacramento Valley by Friday afternoon. Daytime highs will cool slightly on Friday then much more on Saturday as the upper low continues southward through Northern California. This low will bring showers and afternoon isolated/evening thunderstorms to most of the area. Anyone planning weekend outdoor activities should be prepared for periods of wet weather and should be prepared to take shelter if thunderstorms develop. Daytime highs are expected to drop to 10–15° below normal, which is the low 70s for the valley and Delta. (Ek) 

ANOTHER UPPER LOW DROPS SOUTHWARD OUT OF WESTERN CANADA THURSDAY
NIGHT WILL NUDGE THE GREAT BASIN LOW EASTWARD BRINGING A TEMPORARY
DRY PERIOD THURSDAY NIGHT AND FRIDAY MORNING. THIS BREAK WILL BE
SHORT LIVED HOWEVER WITH THE UPPER LOW APPROACHING NORCAL WITH A
THREAT OF SHOWERS OR THUNDERSTORMS FOR THE MOUNTAINS AND THE
NORTHERN SACRAMENTO VALLEY BY FRIDAY AFTERNOON. DAYTIME HIGHS
WILL COOL SLIGHTLY ON FRIDAY THEN MUCH MORE ON SATURDAY AS THE
UPPER LOW CONTINUES SOUTHWARD THROUGH NORTHERN CALIFORNIA. THIS
LOW WILL BRING SHOWERS AND AFTERNOON ISOLATED/EVENING
THUNDERSTORMS TO MOST OF THE AREA. ANYONE PLANNING WEEKEND OUTDOOR
ACTIVITIES SHOULD BE PREPARED FOR PERIODS OF WET WEATHER AND
SHOULD BE PREPARED TO TAKE SHELTER IF THUNDERSTORMS DEVELOP. DAYTIME
HIGHS ARE EXPECTED TO DROP TO 10 TO 15 DEGREES BELOW NORMAL, WHICH
IS THE LOW 70S FOR THE VALLEY AND DELTA. EK [DISC]

Extended discussion (Sunday through Wednesday) a closed upper low will be tracking across California towards the southwest CONUS [Continental US] Sunday into Monday. Ensembles have been consistent in indicating the potential for precipitation both on Sunday and Monday. The better chances for showers and storms look to be in the foothill and mountain regions Sunday, although light valley rain will still be possible. Models indicate some instability mainly north of I-80 across the area and have kept the mention for scattered thunder on Sunday afternoon. Lingering precipitation will be seen on Memorial Day. Models have a bit less instability this day and have left the mention of thunder out at this time. From here, dry valley conditions should be seen through mid week with small precipitation chances at higher elevations. Temperatures will be back on the rise Sunday through Wednesday, with valley highs back into the 80s by Wednesday afternoon. 

.EXTENDED DISCUSSION (SUNDAY THROUGH WEDNESDAY)
A CLOSED UPPER LOW WILL BE TRACKING ACROSS CALIFORNIA TOWARDS THE
SOUTHWEST CONUS SUNDAY INTO MONDAY. ENSEMBLES HAVE BEEN
CONSISTENT IN INDICATING THE POTENTIAL FOR PRECIPITATION BOTH ON
SUNDAY AND MONDAY. THE BETTER CHANCES FOR SHOWERS AND STORMS LOOK
TO BE IN THE FOOTHILL AND MOUNTAIN REGIONS SUNDAY, ALTHOUGH LIGHT
VALLEY RAIN WILL STILL BE POSSIBLE. MODELS INDICATE SOME
INSTABILITY MAINLY NORTH OF I-80 ACROSS THE AREA AND HAVE KEPT THE
MENTION FOR SCATTERED THUNDER ON SUNDAY AFTERNOON. LINGERING
PRECIPITATION WILL BE SEEN ON MEMORIAL DAY. MODELS HAVE A BIT LESS
INSTABILITY THIS DAY AND HAVE LEFT THE MENTION OF THUNDER OUT AT
THIS TIME. FROM HERE, DRY VALLEY CONDITIONS SHOULD BE SEEN THROUGH
MID WEEK WITH SMALL PRECIPITATION CHANCES AT HIGHER ELEVATIONS.
TEMPERATURES WILL BE BACK ON THE RISE SUNDAY THROUGH WEDNESDAY,
WITH VALLEY HIGHS BACK INTO THE 80S BY WEDNESDAY AFTERNOON. [DISC]

Aviation.  

.AVIATION... [AVIA]

"backwash" cloudiness will be spreading swward over Northern California as upper low moves from Southern California neward into Utah. Most of Northern California will remain VFR [Visual Flight Rules], however local MVFR [Marginal Visual Flight Rules] conditions in showers and isolated thunderstorms can be expected over the W slope Sierra with higher terrain obscured. Lesser chance of a shower/storm over the coastal range. Areas of northerly surface wind gusts up to 30 kts [35 mph] possible in the valley through 03Z [8pm PDT] Thursday, and over the west side of the valley overnite. Local NE to E winds over the Sierra gusting to 45 kts [52 mph] overnite. 

"BACKWASH" CLOUDINESS WILL BE SPREADING SWWARD OVER NORCAL AS
UPPER LOW MOVES FROM SOCAL NEWARD INTO UTAH. MOST OF NORCAL WILL
REMAIN VFR, HOWEVER LOCAL MVFR CONDITIONS IN SHOWERS AND ISOLATED
THUNDERSTORMS CAN BE EXPECTED OVER THE W SLOPE SIERRA WITH HIGHER
TERRAIN OBSCURED. LESSER CHANCE OF A SHOWER/STORM OVER THE COASTAL
RANGE. AREAS OF NLY SURFACE WIND GUSTS UP TO 30 KTS POSSIBLE IN
THE VLY THROUGH 03Z THU, AND OVER THE WEST SIDE OF THE VLY
OVERNITE. LOCAL NE TO E WINDS OVER THE SIERRA GUSTING TO 45 KTS
OVERNITE. [AVI2]

STO [Sacramento/WFO CA] Watches/Warnings/Advisories

  • None. 
.STO WATCHES/WARNINGS/ADVISORIES...
NONE. [WARN]

Point Forecast

Mather CA

22 May 3:55pm PDT

Tonight Mostly cloudy, with a low around 53°. NW wind 8 to 14 mph becoming ESE in the evening. Winds could gust as high as 21 mph.
Thursday Mostly sunny, with a high near 77°. NW wind 6 to 9 mph becoming south in the morning.
Thursday Night Partly cloudy, with a low around 54°. SE wind 5 to 15 mph, with gusts as high as 23 mph.
Friday Mostly sunny, with a high near 78°. SW wind 6 to 10 mph.
Friday Night A 20% chance of showers. Mostly cloudy, with a low around 53°. SSE wind around 7 mph.
Saturday A slight chance of showers, then a chance of showers and thunderstorms after 11am. Partly sunny, with a high near 72°. Chance of precipitation is 30%.
Saturday Night A slight chance of showers and thunderstorms. Partly cloudy, with a low around 51°. Chance of precipitation is 20%.
Sunday A chance of showers. Partly sunny, with a high near 70°.
Sunday Night A slight chance of showers before 11pm. Mostly cloudy, with a low around 51°.
Memorial Day A slight chance of showers. Mostly sunny, with a high near 74°.
Monday Night Partly cloudy, with a low around 52°.
Tuesday Mostly sunny, with a high near 79°.
Tuesday Night Mostly clear, with a low around 54°.
Wednesday Sunny, with a high near 83°.
Tonight
Mostly cloudy, with a low around 53. Northwest wind 8 to 14 mph becoming east southeast in the evening. Winds could gust as high as 21 mph.
Thursday
Mostly sunny, with a high near 77. Northwest wind 6 to 9 mph becoming south in the morning.
Thursday Night
Partly cloudy, with a low around 54. Southeast wind 5 to 15 mph, with gusts as high as 23 mph.
Friday
Mostly sunny, with a high near 78. Southwest wind 6 to 10 mph.
Friday Night
A 20 percent chance of showers. Mostly cloudy, with a low around 53. South southeast wind around 7 mph.
Saturday
A slight chance of showers, then a chance of showers and thunderstorms after 11am. Partly sunny, with a high near 72. Chance of precipitation is 30%.
Saturday Night
A slight chance of showers and thunderstorms. Partly cloudy, with a low around 51. Chance of precipitation is 20%.
Sunday
A chance of showers. Partly sunny, with a high near 70.
Sunday Night
A slight chance of showers before 11pm. Mostly cloudy, with a low around 51.
Memorial Day
A slight chance of showers. Mostly sunny, with a high near 74.
Monday Night
Partly cloudy, with a low around 52.
Tuesday
Mostly sunny, with a high near 79.
Tuesday Night
Mostly clear, with a low around 54.
Wednesday
Sunny, with a high near 83.

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