Area Forecast Discussion
FXUS66 KSTO [Sacramento/WFO CA] 131648 AFDSTO ∨
FXUS66 KSTO 131648 AFDSTO [HEAD]
National Weather Service Sacramento California 8:48am PST Fri Dec 13 2013 ∨
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SACRAMENTO CA 848 AM PST FRI DEC 13 2013 [HEAD]
Synopsis. Dry, high pressure dominates the West Coast at least into early next week, as temperatures will continue to warm. The potential exists for more cold frontal impacts over Northern California this Wednesday/Thursday. ∨
.SYNOPSIS... DRY, HIGH PRESSURE DOMINATES THE WEST COAST AT LEAST INTO EARLY NEXT WEEK, AS TEMPERATURES WILL CONTINUE TO WARM. THE POTENTIAL EXISTS FOR MORE COLD FRONTAL IMPACTS OVER NORTHERN CALIFORNIA THIS WEDNESDAY/THURSDAY. [DISC]
Short term discussion (today through Monday)… several valley sites hit at or below freezing early this morning as skies cleared out quickly from the passing weak trough overnight. Areas of frost and patchy fog developed for some locations low-lying valley locations. However, temperatures are a few degrees warmer this morning than this time yesterday. No updates to the previous forecast this morning. (Shen) ∨
.SHORT TERM DISCUSSION (TODAY THROUGH MONDAY)... SEVERAL VALLEY SITES HIT AT OR BELOW FREEZING EARLY THIS MORNING AS SKIES CLEARED OUT QUICKLY FROM THE PASSING WEAK TROUGH OVERNIGHT. AREAS OF FROST AND PATCHY FOG DEVELOPED FOR SOME LOCATIONS LOW-LYING VALLEY LOCATIONS. HOWEVER, TEMPERATURES ARE A FEW DEGREES WARMER THIS MORNING THAN THIS TIME YESTERDAY. NO UPDATES TO THE PREVIOUS FORECAST THIS MORNING. SHEN [DISC]
Previous discussion. A ridge will build over the region behind this system today and Saturday to keep the region dry with cool nights and mild afternoon temperatures. The warming trend this weekend into early next week could could raise temperatures 5–15°F above normal. The warming will be aided by some adiabatic warming from the mild northerly to northeasterly winds. Therefore, fog is not a big concern, but some patchy shallow ground fog may start to develop over the weekend near the waterways and flooded Rice fields from around the sutter buttes/Butte sink southward. The fields around Sacramento International Airport, including adjacent I-5, are usually a magnet for this type of patchy ground fog. (Jclapp) ∨
...PREVIOUS DISCUSSION... A RIDGE WILL BUILD OVER THE REGION BEHIND THIS SYSTEM TODAY AND SATURDAY TO KEEP THE REGION DRY WITH COOL NIGHTS AND MILD AFTERNOON TEMPERATURES. THE WARMING TREND THIS WEEKEND INTO EARLY NEXT WEEK COULD COULD RAISE TEMPERATURES 5 TO 15 DEGREE F ABOVE NORMAL. THE WARMING WILL BE AIDED BY SOME ADIABATIC WARMING FROM THE MILD NORTHERLY TO NORTHEASTERLY WINDS. THEREFORE, FOG IS NOT A BIG CONCERN, BUT SOME PATCHY SHALLOW GROUND FOG MAY START TO DEVELOP OVER THE WEEKEND NEAR THE WATERWAYS AND FLOODED RICE FIELDS FROM AROUND THE SUTTER BUTTES/BUTTE SINK SOUTHWARD. THE FIELDS AROUND SACRAMENTO INTERNATIONAL AIRPORT, INCLUDING ADJACENT I-5, ARE USUALLY A MAGNET FOR THIS TYPE OF PATCHY GROUND FOG. JCLAPP [DISC]
Extended discussion (Tuesday through Friday) ∨
.EXTENDED DISCUSSION (TUESDAY THROUGH FRIDAY) [DISC]
First part of extended period Tuesday looks dry under upper level ridging. Surface high pressure over the Great Basin combined with an upper low off the central California coast will bring breezy east winds down some Sierra canyons during the morning hours. The upper ridge is expected to flatten just a bit on Tuesday but daytime highs are still forecast to come in as much as 10° above normal for the time of year. A Gulf of Alaska frontal system is forecast to kick the weak offshore low inland on Wednesday. Although no precipitation is expected from this low… most areas will see increased cloudiness and slightly cooler temperatures. The frontal system is forecast to drop into the Pacific Northwest on Wednesday but models vary on timing. ECMWF [European Center for Medium-Range Weather Forecasts model] and GEM [Global Environmental Multiscale model] would bring precipitation threat into far Northern California by Wednesday afternoon. Much slower 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.] holds off until late Wednesday night and latest 06Z [10pm PST] 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.] run holds off until Thursday morning before bringing precipitation threat to Northern California. No matter what the timing… this inside slider type system looks to be quite dry with precipitable water values forecast at well under 1/2 inch. Therefore… any precipitation amount would be small. Trough axis passage is currently forecast for Thursday either early or late depending on model and this will be the time any light precipitation will be most likely although again… any precipitation amounts would be very limited. Dry northerly flow develops behind this system on Friday ending any precipitation threat. Current model projections would indicate a fairly breezy Friday going into the weekend with daytime highs by the end of next week closer to normal for mid December. ∨
FIRST PART OF EXTENDED PERIOD TUESDAY LOOKS DRY UNDER UPPER LEVEL RIDGING. SURFACE HIGH PRESSURE OVER THE GREAT BASIN COMBINED WITH AN UPPER LOW OFF THE CENTRAL CALIFORNIA COAST WILL BRING BREEZY EAST WINDS DOWN SOME SIERRA CANYONS DURING THE MORNING HOURS. THE UPPER RIDGE IS EXPECTED TO FLATTEN JUST A BIT ON TUESDAY BUT DAYTIME HIGHS ARE STILL FORECAST TO COME IN AS MUCH AS 10 DEGREES ABOVE NORMAL FOR THE TIME OF YEAR. A GULF OF ALASKA FRONTAL SYSTEM IS FORECAST TO KICK THE WEAK OFFSHORE LOW INLAND ON WEDNESDAY. ALTHOUGH NO PRECIPITATION IS EXPECTED FROM THIS LOW...MOST AREAS WILL SEE INCREASED CLOUDINESS AND SLIGHTLY COOLER TEMPERATURES. THE FRONTAL SYSTEM IS FORECAST TO DROP INTO THE PACIFIC NORTHWEST ON WEDNESDAY BUT MODELS VARY ON TIMING. ECMWF AND GEM WOULD BRING PRECIP THREAT INTO FAR NORCAL BY WEDNESDAY AFTERNOON. MUCH SLOWER GFS HOLDS OFF UNTIL LATE WEDNESDAY NIGHT AND LATEST 06Z GFS RUN HOLDS OFF UNTIL THURSDAY MORNING BEFORE BRINGING PRECIP THREAT TO NORCAL. NO MATTER WHAT THE TIMING...THIS INSIDE SLIDER TYPE SYSTEM LOOKS TO BE QUITE DRY WITH PRECIPITABLE WATER VALUES FORECAST AT WELL UNDER 1/2 INCH. THEREFORE...ANY PRECIP AMOUNT WOULD BE SMALL. TROUGH AXIS PASSAGE IS CURRENTLY FORECAST FOR THURSDAY EITHER EARLY OR LATE DEPENDING ON MODEL AND THIS WILL BE THE TIME ANY LIGHT PRECIP WILL BE MOST LIKELY ALTHOUGH AGAIN...ANY PRECIP AMOUNTS WOULD BE VERY LIMITED. DRY NORTHERLY FLOW DEVELOPS BEHIND THIS SYSTEM ON FRIDAY ENDING ANY PRECIP THREAT. CURRENT MODEL PROJECTIONS WOULD INDICATE A FAIRLY BREEZY FRIDAY GOING INTO THE WEEKEND WITH DAYTIME HIGHS BY THE END OF NEXT WEEK CLOSER TO NORMAL FOR MID DECEMBER. [DISC]
Mainly VFR [Visual Flight Rules] scattered clouds conditions through Saturday morning… except local MVFR [Marginal Visual Flight Rules]/IFR [Instrument Flight Rules] haze/mist in the southern Sacramento and northern San Joaquin Valleys mainly during the morning hours. Light northerly flow over the TAF [Terminal Aerodrome Forecast] sites. Local NE to E winds 10–25 kts [12–29 mph] over Sierra and coastal range mountains. ∨
MAINLY VFR SKC CONDITIONS THROUGH SAT MORNING...EXCEPT LOCAL MVFR/IFR HZ/BR IN THE SOUTHERN SACRAMENTO AND NORTHERN SAN JOAQUIN VALLEYS MAINLY DURING THE MORNING HOURS. LIGHT NLY FLOW OVER THE TAF SITES. LOCAL NE TO E WINDS 10-25 KTS OVER SIERRA AND COASTAL RANGE MTNS. [AVI2]
STO [Sacramento/WFO CA] Watches/Warnings/Advisories
.STO WATCHES/WARNINGS/ADVISORIES... NONE. [WARN]
18 Miles E Groveland CA
2:31am PST Dec 13 2013
This Afternoon. Sunny, with a high near 48°. Light NNW wind.
Tonight. Clear, with a low around 30°. ENE wind around 11 mph.
Saturday. Sunny, with a high near 54°. ENE wind 6 to 11 mph becoming light NNE in the afternoon. Winds could gust as high as 18 mph.
Saturday Night. Mostly clear, with a low around 34°. ENE wind 9 to 11 mph.
Sunday. Sunny, with a high near 57°. ENE wind 7 to 11 mph.
Sunday Night. Mostly clear, with a low around 37°.
Monday. Sunny, with a high near 61°.
Monday Night. Mostly clear, with a low around 39°.
Tuesday. Mostly sunny, with a high near 60°.
Tuesday Night. Partly cloudy, with a low around 39°.
Wednesday. Mostly sunny, with a high near 54°.
Wednesday Night. Partly cloudy, with a low around 36°.
Thursday. Mostly sunny, with a high near 41°.