Area Forecast Discussion
FXUS66 KSTO [Sacramento/WFO CA] 301036 AFDSTO ∨
FXUS66 KSTO 301036 AFDSTO [HEAD]
National Weather Service Sacramento California 3:36am PDT Thu Oct 30 2014 ∨
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SACRAMENTO CA 336 AM PDT THU OCT 30 2014 [HEAD]
Synopsis. Mild weather for today under upper level high pressure. A cold front will impact interior Northern California beginning tonight then moving through Northern California on Friday. The front will bring rain and mountain snow along with cooler temperatures, and a slight chance of thunderstorms. Showers are expected behind the front on Saturday. Snow levels will lower to around 4500 ft Saturday morning. Showers ending early Sunday with drier and milder weather early next week. ∨
.SYNOPSIS... MILD WEATHER FOR TODAY UNDER UPPER LEVEL HIGH PRESSURE. A COLD FRONT WILL IMPACT INTERIOR NORTHERN CALIFORNIA BEGINNING TONIGHT THEN MOVING THROUGH NORCAL ON FRIDAY. THE FRONT WILL BRING RAIN AND MOUNTAIN SNOW ALONG WITH COOLER TEMPERATURES, AND A SLIGHT CHANCE OF THUNDERSTORMS. SHOWERS ARE EXPECTED BEHIND THE FRONT ON SATURDAY. SNOW LEVELS WILL LOWER TO AROUND 4500 FT SATURDAY MORNING. SHOWERS ENDING EARLY SUNDAY WITH DRIER AND MILDER WEATHER EARLY NEXT WEEK. [DISC]
Discussion. Forecast area under mainly fair skies this morning under high pressure ridge currently over the Western US a Pacific frontal system will be pushing this ridge eastward over the next few days bringing a significant change in the weather pattern. High cloudiness being pulled northward into the area today ahead of an offshore cold front will bring the first signs of weather pattern change. Daytime highs will cool slightly from Wednesday but still remain a little above normal for this time of year. The Pacific cold front is forecast to move into Northern California on Friday bringing rain and mountain snow and enough instability for a slight threat of thunderstorms especially over the western half of the CWA [County Warning Area; see the LWP home page (link at bottom of page) for a CWA map]. Model timing of this frontal system is becoming more consistent amongst the models with current timing putting the frontal boundary over the Central Valley around 00Z [5pm PDT] Friday. Not real good timing for trick or treaters who will be under the rainy effects of the back edge of the front early Friday evening. By 12Z [5am PDT] Saturday morning the main frontal band should be over the Sierra. Colder air filtering in behind this front will bring a rapid drop in snow levels. By 12Z [5am PDT] Saturday… snow levels over the CWA [County Warning Area; see the LWP home page (link at bottom of page) for a CWA map] should range from 4000–5000 feet. Showers are likely on Saturday under upper level cyclonic [counterclockwise] flow. Saturday afternoon highs under the cooler airmass are forecast to come in around 10° below normal. Mid range models move the upper trough axis into the Great Basin by 12Z [5am PDT] Sunday morning. Rebuilding high pressure will bring an end to any precipitation threat by Sunday afternoon along with the beginning of a warming trend. ∨
.DISCUSSION... FORECAST AREA UNDER MAINLY FAIR SKIES THIS MORNING UNDER HIGH PRESSURE RIDGE CURRENTLY OVER THE WESTERN U.S. A PACIFIC FRONTAL SYSTEM WILL BE PUSHING THIS RIDGE EASTWARD OVER THE NEXT FEW DAYS BRINGING A SIGNIFICANT CHANGE IN THE WEATHER PATTERN. HIGH CLOUDINESS BEING PULLED NORTHWARD INTO THE AREA TODAY AHEAD OF AN OFFSHORE COLD FRONT WILL BRING THE FIRST SIGNS OF WEATHER PATTERN CHANGE. DAYTIME HIGHS WILL COOL SLIGHTLY FROM WEDNESDAY BUT STILL REMAIN A LITTLE ABOVE NORMAL FOR THIS TIME OF YEAR. THE PACIFIC COLD FRONT IS FORECAST TO MOVE INTO NORTHERN CALIFORNIA ON FRIDAY BRINGING RAIN AND MOUNTAIN SNOW AND ENOUGH INSTABILITY FOR A SLIGHT THREAT OF THUNDERSTORMS ESPECIALLY OVER THE WESTERN HALF OF THE CWA. MODEL TIMING OF THIS FRONTAL SYSTEM IS BECOMING MORE CONSISTENT AMONGST THE MODELS WITH CURRENT TIMING PUTTING THE FRONTAL BOUNDARY OVER THE CENTRAL VALLEY AROUND 00Z FRIDAY. NOT REAL GOOD TIMING FOR TRICK OR TREATERS WHO WILL BE UNDER THE RAINY EFFECTS OF THE BACK EDGE OF THE FRONT EARLY FRIDAY EVENING. BY 12Z SATURDAY MORNING THE MAIN FRONTAL BAND SHOULD BE OVER THE SIERRA. COLDER AIR FILTERING IN BEHIND THIS FRONT WILL BRING A RAPID DROP IN SNOW LEVELS. BY 12Z SATURDAY...SNOW LEVELS OVER THE CWA SHOULD RANGE FROM 4000 TO 5000 FEET. SHOWERS ARE LIKELY ON SATURDAY UNDER UPPER LEVEL CYCLONIC FLOW. SATURDAY AFTERNOON HIGHS UNDER THE COOLER AIRMASS ARE FORECAST TO COME IN AROUND 10 DEGREES BELOW NORMAL. MID RANGE MODELS MOVE THE UPPER TROUGH AXIS INTO THE GREAT BASIN BY 12Z SUNDAY MORNING. REBUILDING HIGH PRESSURE WILL BRING AN END TO ANY PRECIPITATION THREAT BY SUNDAY AFTERNOON ALONG WITH THE BEGINNING OF A WARMING TREND. [DISC]
Extended discussion (Monday through Thursday) ∨
.EXTENDED DISCUSSION (MONDAY THROUGH THURSDAY) [DISC]
High pressure ridging along the West Coast will be the dominant weather feature through the extended period. Daytime highs will slowly be climbing Monday through Thursday reaching to around normal. Extended models move a weak system over the north end of the ridge and into the Pacific Northwest around Tuesday but keep any precipitation north of the forecast area. Therefore… extended period remains dry for now. Extended models hinting at a return to a wetter pattern towards the end of next week but have been rather inconsistent both run to run and model to model so confidence in this change not especially high at this time. ∨
HIGH PRESSURE RIDGING ALONG THE WEST COAST WILL BE THE DOMINANT WEATHER FEATURE THROUGH THE EXTENDED PERIOD. DAYTIME HIGHS WILL SLOWLY BE CLIMBING MONDAY THROUGH THURSDAY REACHING TO AROUND NORMAL. EXTENDED MODELS MOVE A WEAK SYSTEM OVER THE NORTH END OF THE RIDGE AND INTO THE PACIFIC NORTHWEST AROUND TUESDAY BUT KEEP ANY PRECIPITATION NORTH OF THE FORECAST AREA. THEREFORE...EXTENDED PERIOD REMAINS DRY FOR NOW. EXTENDED MODELS HINTING AT A RETURN TO A WETTER PATTERN TOWARDS THE END OF NEXT WEEK BUT HAVE BEEN RATHER INCONSISTENT BOTH RUN TO RUN AND MODEL TO MODEL SO CONFIDENCE IN THIS CHANGE NOT ESPECIALLY HIGH AT THIS TIME. [DISC]
VFR [Visual Flight Rules] conditions expected to continue the next 24 hours. A frontal system will begin to approach the area tonight, with light showers spreading across the coastal range after midnight tonight. Light winds across the valley this morning will become southerly up to 10 kt [12 mph]. Along the mountains, SW wind gusts up to 30 kt [35 mph] will be possible this afternoon. ∨
VFR CONDITIONS EXPECTED TO CONTINUE THE NEXT 24 HOURS. A FRONTAL SYSTEM WILL BEGIN TO APPROACH THE AREA TONIGHT, WITH LIGHT SHOWERS SPREADING ACROSS THE COASTAL RANGE AFTER MIDNIGHT TONIGHT. LIGHT WINDS ACROSS THE VALLEY THIS MORNING WILL BECOME SOUTHERLY UP TO 10 KT. ALONG THE MOUNTAINS, SW WIND GUSTS UP TO 30 KT WILL BE POSSIBLE THIS AFTERNOON. [AVI2]
STO [Sacramento/WFO CA] Watches/Warnings/Advisories
.STO WATCHES/WARNINGS/ADVISORIES... WINTER STORM WATCH FROM FRIDAY MORNING THROUGH SATURDAY AFTERNOON ABOVE 5000 FEET IN THE WEST SLOPE NORTHERN SIERRA NEVADA...WESTERN PLUMAS COUNTY/LASSEN PARK. [WARN]
18 Miles E Groveland CA
2:11am PDT Oct 30 2014
Today. Mostly sunny, with a high near 71°. ENE wind 7 to 10 mph becoming SSW in the afternoon.
Tonight. Partly cloudy, with a low around 49°. SSW wind 5 to 8 mph becoming light and variable.
Friday. A slight chance of rain, then a chance of rain and thunderstorms after 11am. Mostly cloudy, with a high near 61°. ESE wind 5 to 14 mph becoming SSW in the afternoon. Winds could gust as high as 21 mph. Chance of precipitation is 50%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.
Friday Night. Rain showers. Low around 39°. SSW wind 6 to 11 mph becoming light south in the evening. Chance of precipitation is 90%. New precipitation amounts between three quarters and one inch possible.
Saturday. Rain and snow showers likely. Mostly cloudy, with a high near 46°. Calm wind becoming SSW 5 to 9 mph in the afternoon. Chance of precipitation is 60%. Little or no snow accumulation expected.
Saturday Night. A slight chance of rain and snow showers. Mostly cloudy, with a low around 33°. Chance of precipitation is 20%.
Sunday. Sunny, with a high near 52°.
Sunday Night. Mostly clear, with a low around 36°.
Monday. Sunny, with a high near 57°.
Monday Night. Mostly clear, with a low around 40°.
Tuesday. Sunny, with a high near 62°.
Tuesday Night. Mostly clear, with a low around 47°.
Wednesday. Sunny, with a high near 66°.