Area Forecast Discussion
FXUS66 KSTO [Sacramento/WFO CA] 272151 AFDSTO ∨
FXUS66 KSTO 272151 AFDSTO [HEAD]
National Weather Service Sacramento California 2:51pm PDT Sun Jul 27 2014 ∨
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SACRAMENTO CA 251 PM PDT SUN JUL 27 2014 [HEAD]
Synopsis. Moisture surge bringing a few sprinkles and isolated thunderstorms to portions of interior Northern California today, and this pattern will continue into mid-week. The increase in clouds and return of the Delta breeze will result in a little cooler temps for the Central Valley the next few days. ∨
.SYNOPSIS... MOISTURE SURGE BRINGING A FEW SPRINKLES AND ISOLATED THUNDERSTORMS TO PORTIONS OF INTERIOR NORCAL TODAY, AND THIS PATTERN WILL CONTINUE INTO MID-WEEK. THE INCREASE IN CLOUDS AND RETURN OF THE DELTA BREEZE WILL RESULT IN A LITTLE COOLER TEMPS FOR THE CENTRAL VALLEY THE NEXT FEW DAYS. [DISC]
Discussion. Band of clouds along the western edge of the monsoon surge of mid and upper-level moisture continues to move up from the south through the middle portion of the forecast area. Virga and a few sprinkles have been occurring with some of the deeper convection, but so far thunderstorm activity along the band has remained along the coast or offshore to the south and southwest of the Bay Area. A few storms have begun to develop over the northern Sierra to the south of Lake Tahoe at mid-afternoon. ∨
.DISCUSSION... BAND OF CLOUDS ALONG THE WESTERN EDGE OF THE MONSOON SURGE OF MID AND UPPER-LEVEL MOISTURE CONTINUES TO MOVE UP FROM THE SOUTH THROUGH THE MIDDLE PORTION OF THE FORECAST AREA. VIRGA AND A FEW SPRINKLES HAVE BEEN OCCURRING WITH SOME OF THE DEEPER CONVECTION, BUT SO FAR THUNDERSTORM ACTIVITY ALONG THE BAND HAS REMAINED ALONG THE COAST OR OFFSHORE TO THE SOUTH AND SOUTHWEST OF THE BAY AREA. A FEW STORMS HAVE BEGUN TO DEVELOP OVER THE NORTHERN SIERRA TO THE SOUTH OF LAKE TAHOE AT MID-AFTERNOON. [DISC]
Clouds have held temperatures down through much of the day through the Central Valley, but readings are rallying at mid-afternoon as more sunshine has peeked through and are now mostly in the 90s. Looks like we'll still end up shy of the century mark today in Sacramento, but it may be close. ∨
CLOUDS HAVE HELD TEMPERATURES DOWN THROUGH MUCH OF THE DAY THROUGH THE CENTRAL VALLEY, BUT READINGS ARE RALLYING AT MID-AFTERNOON AS MORE SUNSHINE HAS PEEKED THROUGH AND ARE NOW MOSTLY IN THE 90S. LOOKS LIKE WE`LL STILL END UP SHY OF THE CENTURY MARK TODAY IN SACRAMENTO, BUT IT MAY BE CLOSE. [DISC]
Tricky forecast the next few days with plenty of mid and upper-level moisture remaining over the area with elevated instability. Looks like the entrance region of the upper jet arcing over the Western US ridge will remain overhead, and any weak perturbations coming up from the south may be enough to kick off a few showers and thunderstorms. Water vapor imagery shows a few stronger waves to our south - one originating from the large thunderstorm complex over SW Arizona last night and another moving up the West Coast of Baja - that bear watching over the day or so. Latest timing of these would place them up around the Sacramento area Monday night and early Tuesday. ∨
TRICKY FORECAST THE NEXT FEW DAYS WITH PLENTY OF MID AND UPPER- LEVEL MOISTURE REMAINING OVER THE AREA WITH ELEVATED INSTABILITY. LOOKS LIKE THE ENTRANCE REGION OF THE UPPER JET ARCING OVER THE WESTERN US RIDGE WILL REMAIN OVERHEAD, AND ANY WEAK PERTURBATIONS COMING UP FROM THE SOUTH MAY BE ENOUGH TO KICK OFF A FEW SHOWERS AND THUNDERSTORMS. WATER VAPOR IMAGERY SHOWS A FEW STRONGER WAVES TO OUR SOUTH - ONE ORIGINATING FROM THE LARGE THUNDERSTORM COMPLEX OVER SW AZ LAST NIGHT AND ANOTHER MOVING UP THE WEST COAST OF BAJA - THAT BEAR WATCHING OVER THE DAY OR SO. LATEST TIMING OF THESE WOULD PLACE THEM UP AROUND THE SACRAMENTO AREA MONDAY NIGHT AND EARLY TUESDAY. [DISC]
Temperatures will also be tricky depending on cloud cover (and the strength of the Delta breeze for the SAC [Sacramento CA] region), but will likely remain rather hot through at least the early portion of the week. ∨
TEMPERATURES WILL ALSO BE TRICKY DEPENDING ON CLOUD COVER (AND THE STRENGTH OF THE DELTA BREEZE FOR THE SAC REGION), BUT WILL LIKELY REMAIN RATHER HOT THROUGH AT LEAST THE EARLY PORTION OF THE WEEK. [DISC]
Extended discussion (Thursday through Sunday). Models show the western CONUS [Continental US] ridge maintaining it's position over the intermountain Rockies through the extended, Thursday to Sunday, with fairly weak S to SSW flow aloft. The resultant flow aloft will bring some monsoonal moisture northward into the Sierra. Therefore, we have left a minimal thunderstorm threat over the Sierra Crest south of Highway 50 and around the periphery of Shasta County. Temperatures remain around normal, with the mid to upper 90s in the valley and 70s to 90s in the mountains/foothills. Of course, temperatures will depend on the resultant cloud cover. ∨
.EXTENDED DISCUSSION (THURSDAY THROUGH SUNDAY)... MODELS SHOW THE WESTERN CONUS RIDGE MAINTAINING IT`S POSITION OVER THE INTERMOUNTAIN ROCKIES THROUGH THE EXTENDED, THURSDAY TO SUNDAY, WITH FAIRLY WEAK S TO SSW FLOW ALOFT. THE RESULTANT FLOW ALOFT WILL BRING SOME MONSOONAL MOISTURE NORTHWARD INTO THE SIERRA. THEREFORE, WE HAVE LEFT A MINIMAL THUNDERSTORM THREAT OVER THE SIERRA CREST SOUTH OF HIGHWAY 50 AND AROUND THE PERIPHERY OF SHASTA COUNTY. TEMPERATURES REMAIN AROUND NORMAL, WITH THE MID TO UPPER 90S IN THE VALLEY AND 70S TO 90S IN THE MOUNTAINS/FOOTHILLS. OF COURSE, TEMPERATURES WILL DEPEND ON THE RESULTANT CLOUD COVER. [DISC]
The ECMWF [European Center for Medium-Range Weather Forecasts model] and GEM [Global Environmental Multiscale model] models show an embedded weak low feature aloft moving northward into Nevada by Saturday/Sunday, and could add some instability over Northern California. However, we didn't bit on any additional convective coverage this feature this far out as it is very subtle at this point. (Jclapp) ∨
THE ECMWF AND GEM MODELS SHOW AN EMBEDDED WEAK LOW FEATURE ALOFT MOVING NORTHWARD INTO NV BY SATURDAY/SUNDAY, AND COULD ADD SOME INSTABILITY OVER NORTHERN CA. HOWEVER, WE DIDN`T BIT ON ANY ADDITIONAL CONVECTIVE COVERAGE THIS FEATURE THIS FAR OUT AS IT IS VERY SUBTLE AT THIS POINT. JCLAPP [DISC]
Aviation. Mainly VFR [Visual Flight Rules] next 24 hours, except areas of smoke near the sand fire. Potential TS [thunderstorm without precipitation (or tropical storm)] over coastal range and Sierra south of Hwy 50 late this afternoon to early evening. Winds will remain below 10–15 kt [12–17 mph] across valley TAF [Terminal Aerodrome Forecast] sites. Near Delta, SW winds 15–25 kt [17–29 mph] continue. (Jclapp) ∨
.AVIATION... MAINLY VFR NEXT 24 HOURS, EXCEPT AREAS OF SMOKE NEAR THE SAND FIRE. POTENTIAL TS OVER COASTAL RANGE AND SIERRA SOUTH OF HWY 50 LATE THIS AFTERNOON TO EARLY EVENING. WINDS WILL REMAIN BELOW 10-15 KT ACROSS VALLEY TAF SITES. NEAR DELTA, SW WINDS 15-25 KT CONTINUE. JCLAPP [AVIA]
STO [Sacramento/WFO CA] Watches/Warnings/Advisories
.STO WATCHES/WARNINGS/ADVISORIES...NONE. [WARN]
18 Miles E Groveland CaSimilar City NA
1:50pm PDT Jul 27 2014
Tonight. A 20% chance of showers and thunderstorms. Mostly cloudy, with a low around 67°. WNW wind around 6 mph becoming ENE after midnight.
Monday. A 30% chance of showers and thunderstorms, mainly after 11am. Partly sunny, with a high near 94°. Calm wind becoming WSW 5 to 7 mph in the afternoon. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.
Monday Night. A 20% chance of showers and thunderstorms. Mostly cloudy, with a low around 64°. Light and variable wind becoming ENE 6 to 11 mph after midnight.
Tuesday. A 20% chance of showers and thunderstorms after 11am. Mostly sunny, with a high near 94°. ENE wind around 11 mph becoming west in the morning. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.
Tuesday Night. A 20% chance of showers and thunderstorms before 11pm. Mostly clear, with a low around 63°. West wind 6 to 14 mph becoming NE in the evening. Winds could gust as high as 21 mph.
Wednesday. Mostly sunny, with a high near 94°.
Wednesday Night. Mostly clear, with a low around 63°.
Thursday. Sunny, with a high near 93°.
Thursday Night. Mostly clear, with a low around 63°.
Friday. Mostly sunny, with a high near 92°.
Friday Night. Partly cloudy, with a low around 62°.
Saturday. Mostly sunny, with a high near 92°.
Saturday Night. Partly cloudy, with a low around 62°.
Sunday. Mostly sunny, with a high near 92°.