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Area Forecast Discussion

FXUS66 KSTO [Sacramento/WFO CA] 022302 AFDSTO 

FXUS66 KSTO 022302
AFDSTO [HEAD]

National Weather Service Sacramento California 4:02pm PDT Tue Jun 2 2015 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
402 PM PDT TUE JUN 2 2015 [HEAD]

Synopsis. Isolated shower and thunderstorm chances will persist through Wednesday over the northern mountains. Better chances for showers and thunderstorms will develop Thursday into the weekend as a storm lingers over California. 

.SYNOPSIS...
ISOLATED SHOWER AND THUNDERSTORM CHANCES WILL PERSIST THROUGH
WEDNESDAY OVER THE NORTHERN MOUNTAINS. BETTER CHANCES FOR SHOWERS
AND THUNDERSTORMS WILL DEVELOP THURSDAY INTO THE WEEKEND AS A
STORM LINGERS OVER CA. [DISC]

Discussion. Temperatures running about 1–6° warmer than 24 hours ago with ample sunshine over much of Northern California. Similar conditions expected tomorrow with the possibility of some patchy morning low clouds in the Delta into the SAC [Sacramento CA] Metro region. There could also be a few isolated showers/thunderstorms over the mountains north of I-80 during afternoon/evening hours. 

.DISCUSSION...
TEMPERATURES RUNNING ABOUT 1-6 DEGREES WARMER THAN 24 HOURS AGO
WITH AMPLE SUNSHINE OVER MUCH OF NORCAL. SIMILAR CONDITIONS
EXPECTED TOMORROW WITH THE POSSIBILITY OF SOME PATCHY MORNING LOW
CLOUDS IN THE DELTA INTO THE SAC METRO REGION. THERE COULD ALSO BE A
FEW ISOLATED SHOWERS/THUNDERSTORMS OVER THE MOUNTAINS NORTH OF
INTERSTATE 80 DURING AFTERNOON/EVENING HOURS. [DISC]

Expect bigger changes Thursday onward. An upper level low will drop southward into Northern California by early Thursday morning. By Thursday afternoon it will strengthen and form a closed low over central California. The atmosphere will become increasingly unstable Thursday through the weekend. Best chances for showers/thunderstorms on Thursday and Friday will be over the mountains and in portions of the northern Sacramento Valley. (JBB) 

EXPECT BIGGER CHANGES THURSDAY ONWARD. AN UPPER LEVEL LOW WILL
DROP SOUTHWARD INTO NORCAL BY EARLY THURSDAY MORNING. BY THURSDAY
AFTERNOON IT WILL STRENGTHEN AND FORM A CLOSED LOW OVER CENTRAL
CA. THE ATMOSPHERE WILL BECOME INCREASINGLY UNSTABLE THURSDAY
THROUGH THE WEEKEND. BEST CHANCES FOR SHOWERS/THUNDERSTORMS ON
THURSDAY AND FRIDAY WILL BE OVER THE MOUNTAINS AND IN PORTIONS OF
THE NORTHERN SACRAMENTO VALLEY. JBB [DISC]

Extended discussion (Saturday through Tuesday). The closed low will linger over central/Southern California on Saturday and start to drift northeastward on Sunday. This will maintain instability over our CWA [County Warning Area; see the LWP home page (link at bottom of page) for a CWA map] across the mountains and into the valley. GFS [Global Forecast System: global spectral model used primarily for aviation weather forecasts; provides guidance out to 384 hours at 00, 06, 12 and 18UTC.] ensembles still show precipitable water in excess of 0.75–1 inch the highest chances of showers/thunderstorms look to be across the mountains, but portions of the valley look to be in play as the low center remains south and east of interior Northern California. Confidence in this occurring has been increasing, but the trajectory of this type of cutoff low [A closed upper-level low which has become completely displaced (cut off) from basic westerly current, and moves independently of that current. Cutoff lows may remain nearly stationary for days, or on occasion may move westward opposite to the prevailing flow aloft] is difficult. Temperatures will cool a few degrees over the weekend and hinge on resulting cloud and precipitation coverage, but will generally be close to normal. (Jclapp) 

.EXTENDED DISCUSSION (SATURDAY THROUGH TUESDAY)...
THE CLOSED LOW WILL LINGER OVER CENTRAL/SOUTHERN CA ON SATURDAY
AND START TO DRIFT NORTHEASTWARD ON SUNDAY. THIS WILL MAINTAIN
INSTABILITY OVER OUR CWA ACROSS THE MOUNTAINS AND INTO THE VALLEY.
GFS ENSEMBLES STILL SHOW PRECIPITABLE WATER IN EXCESS OF 0.75-1 INCH
THE HIGHEST CHANCES OF SHOWERS/THUNDERSTORMS LOOK TO BE ACROSS
THE MOUNTAINS, BUT PORTIONS OF THE VALLEY LOOK TO BE IN PLAY AS
THE LOW CENTER REMAINS SOUTH AND EAST OF INTERIOR NORCAL.
CONFIDENCE IN THIS OCCURRING HAS BEEN INCREASING, BUT THE
TRAJECTORY OF THIS TYPE OF CUTOFF LOW IS DIFFICULT. TEMPERATURES
WILL COOL A FEW DEGREES OVER THE WEEKEND AND HINGE ON RESULTING
CLOUD AND PRECIP COVERAGE, BUT WILL GENERALLY BE CLOSE TO NORMAL.
JCLAPP [DISC]

Aviation. VFR [Visual Flight Rules] conditions expected for most of the period. Periods of MVFR [Marginal Visual Flight Rules] ceilings in the Delta and southern SAC [Sacramento CA] Valley (mainly KSAC [Sacramento CA]/KMHR [Mather Field CA]) Wednesday morning between 14–18Z [7–11am PDT]. Generally light winds with onshore flow… up to 12 kts [14 mph]. (JBB) 

.AVIATION...
VFR CONDITIONS EXPECTED FOR MOST OF THE PERIOD. PERIODS OF
MVFR CIGS IN THE DELTA AND SOUTHERN SAC VALLEY (MAINLY KSAC/KMHR)
WEDNESDAY MORNING BETWEEN 14-18Z. GENERALLY LIGHT WINDS WITH
ONSHORE FLOW...UP TO 12 KTS. JBB [AVIA]

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

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

Point Forecast

Mather CA

Tonight Clear, with a low around 49°. West wind 5 to 7 mph becoming ENE after midnight.
Wednesday Sunny, with a high near 72°. Calm wind becoming WSW 5 to 8 mph in the afternoon.
Wednesday Night Mostly clear, with a low around 51°. West wind around 6 mph becoming light and variable in the evening.
Thursday Mostly sunny, with a high near 70°. Calm wind becoming WSW 5 to 9 mph in the afternoon.
Thursday Night Partly cloudy, with a low around 51°. WSW wind 6 to 9 mph becoming ENE in the evening.
Friday A 20% chance of showers and thunderstorms after 11am. Partly sunny, with a high near 71°.
Friday Night A slight chance of showers and thunderstorms. Mostly cloudy, with a low around 52°. Chance of precipitation is 20%.
Saturday A chance of showers and thunderstorms. Partly sunny, with a high near 71°.
Saturday Night A chance of showers and thunderstorms. Mostly cloudy, with a low around 51°.
Sunday A chance of showers and thunderstorms. Mostly cloudy, with a high near 67°.
Sunday Night A slight chance of showers and thunderstorms. Mostly cloudy, with a low around 52°.
Monday A slight chance of showers. Partly sunny, with a high near 72°.
Monday Night Partly cloudy, with a low around 53°.
Tuesday Mostly sunny, with a high near 78°.
Tonight
Clear, with a low around 49. West wind 5 to 7 mph becoming east northeast after midnight.
Wednesday
Sunny, with a high near 72. Calm wind becoming west southwest 5 to 8 mph in the afternoon.
Wednesday Night
Mostly clear, with a low around 51. West wind around 6 mph becoming light and variable in the evening.
Thursday
Mostly sunny, with a high near 70. Calm wind becoming west southwest 5 to 9 mph in the afternoon.
Thursday Night
Partly cloudy, with a low around 51. West southwest wind 6 to 9 mph becoming east northeast in the evening.
Friday
A 20 percent chance of showers and thunderstorms after 11am. Partly sunny, with a high near 71.
Friday Night
A slight chance of showers and thunderstorms. Mostly cloudy, with a low around 52. Chance of precipitation is 20%.
Saturday
A chance of showers and thunderstorms. Partly sunny, with a high near 71.
Saturday Night
A chance of showers and thunderstorms. Mostly cloudy, with a low around 51.
Sunday
A chance of showers and thunderstorms. Mostly cloudy, with a high near 67.
Sunday Night
A slight chance of showers and thunderstorms. Mostly cloudy, with a low around 52.
Monday
A slight chance of showers. Partly sunny, with a high near 72.
Monday Night
Partly cloudy, with a low around 53.
Tuesday
Mostly sunny, with a high near 78.

This page is generated dynamically from the National Weather Service's NWS point forecast and Area Forecast Discussion, reformatted for readability. NWS glossary; about point forecasts. For more information, visit the Lobitos Weather Project home page. Comments and corrections are welcome: