Area Forecast Discussion FXUS66 KSTO [Sacramento/WFO CA] 242147 AFDSTO ∨ FXUS66 KSTO 242147 AFDSTO [HEAD] National Weather Service Sacramento California 1:47pm PST Sun Nov 24 2024 ∨ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SACRAMENTO CA 147 PM PST SUN NOV 24 2024 [HEAD] Synopsis. A brief lull in precipitation continues through much of this afternoon, before returning to interior Northern California this evening into the week ahead. Periods of rain and moderate to heavy mountain snow are expected through early Wednesday morning, with a brief cool down then to follow into the Thanksgiving holiday. ∨ .SYNOPSIS... A BRIEF LULL IN PRECIPITATION CONTINUES THROUGH MUCH OF THIS AFTERNOON, BEFORE RETURNING TO INTERIOR NORCAL THIS EVENING INTO THE WEEK AHEAD. PERIODS OF RAIN AND MODERATE TO HEAVY MOUNTAIN SNOW ARE EXPECTED THROUGH EARLY WEDNESDAY MORNING, WITH A BRIEF COOL DOWN THEN TO FOLLOW INTO THE THANKSGIVING HOLIDAY. [DISC] *Winter Storm Warning: until 4am Wednesday for elevations above 5500 feet along the Sierra/ southern Cascades including I-80 and Highway 50. ∨ *WINTER STORM WARNING: UNTIL 4 AM WEDNESDAY FOR ELEVATIONS ABOVE 5500 FEET ALONG THE SIERRA/ SOUTHERN CASCADES INCLUDING INTERSTATE 80 AND HIGHWAY 50. [DISC] Discussion. As of early this afternoon, latest goes-west satellite imagery shows some lingering low to mid level cloud cover for valley/foothills locations north of I-80, with some cumulus development elsewhere along the Sierra as well. Despite the cloud cover, the only light radar returns as of the noon hour are along the far northwestern Shasta County Mountains. Otherwise, light to breezy southerly winds prevail with temperatures trending near normal where cloud cover is lacking and slightly below normal elsewhere. ∨ .DISCUSSION... AS OF EARLY THIS AFTERNOON, LATEST GOES-WEST SATELLITE IMAGERY SHOWS SOME LINGERING LOW TO MID LEVEL CLOUD COVER FOR VALLEY/FOOTHILLS LOCATIONS NORTH OF INTERSTATE 80, WITH SOME CUMULUS DEVELOPMENT ELSEWHERE ALONG THE SIERRA AS WELL. DESPITE THE CLOUD COVER, THE ONLY LIGHT RADAR RETURNS AS OF THE NOON HOUR ARE ALONG THE FAR NORTHWESTERN SHASTA COUNTY MOUNTAINS. OTHERWISE, LIGHT TO BREEZY SOUTHERLY WINDS PREVAIL WITH TEMPERATURES TRENDING NEAR NORMAL WHERE CLOUD COVER IS LACKING AND SLIGHTLY BELOW NORMAL ELSEWHERE. [DISC] While this lull in active weather is expected to more or less persist through the remainder of the afternoon, there has been a definitive eastward push over the last few hours of the trough spinning just offshore of Northern California. Even still, the trough is only expected to gradually eject eastward moving into the week ahead. This progression will introduce another period of precipitation impacts to interior Northern California from this evening through early Wednesday morning. This precipitation is expected to arrive in somewhat distinct waves, with areas north of I-80 being influenced by the trough and moisture advected in the immediate vicinity of it, while areas from I-80 southward look to see an additional plume of more concentrated moisture push inland. While overall highest precipitation totals will continue to favor the Sierra, this differential between the attendant moisture should keep valley/foothills precipitation totals more balanced (compared to typical patterns favoring higher totals across the northern Sacramento Valley). ∨ WHILE THIS LULL IN ACTIVE WEATHER IS EXPECTED TO MORE OR LESS PERSIST THROUGH THE REMAINDER OF THE AFTERNOON, THERE HAS BEEN A DEFINITIVE EASTWARD PUSH OVER THE LAST FEW HOURS OF THE TROUGH SPINNING JUST OFFSHORE OF NORCAL. EVEN STILL, THE TROUGH IS ONLY EXPECTED TO GRADUALLY EJECT EASTWARD MOVING INTO THE WEEK AHEAD. THIS PROGRESSION WILL INTRODUCE ANOTHER PERIOD OF PRECIPITATION IMPACTS TO INTERIOR NORCAL FROM THIS EVENING THROUGH EARLY WEDNESDAY MORNING. THIS PRECIPITATION IS EXPECTED TO ARRIVE IN SOMEWHAT DISTINCT WAVES, WITH AREAS NORTH OF INTERSTATE 80 BEING INFLUENCED BY THE TROUGH AND MOISTURE ADVECTED IN THE IMMEDIATE VICINITY OF IT, WHILE AREAS FROM INTERSTATE 80 SOUTHWARD LOOK TO SEE AN ADDITIONAL PLUME OF MORE CONCENTRATED MOISTURE PUSH INLAND. WHILE OVERALL HIGHEST PRECIPITATION TOTALS WILL CONTINUE TO FAVOR THE SIERRA, THIS DIFFERENTIAL BETWEEN THE ATTENDANT MOISTURE SHOULD KEEP VALLEY/FOOTHILLS PRECIPITATION TOTALS MORE BALANCED (COMPARED TO TYPICAL PATTERNS FAVORING HIGHER TOTALS ACROSS THE NORTHERN SACRAMENTO VALLEY). [DISC] Even with the distinct differences in associated moisture plumes across the region, current probabilities of exceeding 1 inch of precipitation sit around 30% to 60% across the valley and foothills, with probabilities of 50% to 70% of exceeding 2 inches of precipitation along the Sierra. Snow levels are expected to fluctuate somewhat through the event, beginning around 4500 feet to 5500 feet this evening into the overnight hours, before briefly rising to 5500 feet to 6500 feet from midday Monday into the evening, then falling back toward 4500–5500 feet overnight Monday through Wednesday morning. As a result, probabilities of exceeding 12 inches of snowfall above 5500 feet are around 50% to 90% along the Sierra, with highest probabilities favored from I-80 southward. ∨ EVEN WITH THE DISTINCT DIFFERENCES IN ASSOCIATED MOISTURE PLUMES ACROSS THE REGION, CURRENT PROBABILITIES OF EXCEEDING 1 INCH OF PRECIPITATION SIT AROUND 30% TO 60% ACROSS THE VALLEY AND FOOTHILLS, WITH PROBABILITIES OF 50% TO 70% OF EXCEEDING 2 INCHES OF PRECIPITATION ALONG THE SIERRA. SNOW LEVELS ARE EXPECTED TO FLUCTUATE SOMEWHAT THROUGH THE EVENT, BEGINNING AROUND 4500 FEET TO 5500 FEET THIS EVENING INTO THE OVERNIGHT HOURS, BEFORE BRIEFLY RISING TO 5500 FEET TO 6500 FEET FROM MIDDAY MONDAY INTO THE EVENING, THEN FALLING BACK TOWARD 4500 TO 5500 FEET OVERNIGHT MONDAY THROUGH WEDNESDAY MORNING. AS A RESULT, PROBABILITIES OF EXCEEDING 12 INCHES OF SNOWFALL ABOVE 5500 FEET ARE AROUND 50% TO 90% ALONG THE SIERRA, WITH HIGHEST PROBABILITIES FAVORED FROM INTERSTATE 80 SOUTHWARD. [DISC] Heaviest snowfall from I-80 southward is anticipated later in the day on Monday through through Tuesday, with primarily lingering snow showers by Wednesday as the trough is finally exiting the region. On the heels of the ejecting trough, a period of breezy northerly winds is expected on Wednesday. This will help usher in a push of colder air to interior Northern California, although coldest temperatures are anticipated Thursday morning. While some patchy low elevation frost may be possible in the northern Sacramento Valley on Wednesday, the breezy winds will likely deter any widespread impacts. ∨ HEAVIEST SNOWFALL FROM INTERSTATE 80 SOUTHWARD IS ANTICIPATED LATER IN THE DAY ON MONDAY THROUGH THROUGH TUESDAY, WITH PRIMARILY LINGERING SNOW SHOWERS BY WEDNESDAY AS THE TROUGH IS FINALLY EXITING THE REGION. ON THE HEELS OF THE EJECTING TROUGH, A PERIOD OF BREEZY NORTHERLY WINDS IS EXPECTED ON WEDNESDAY. THIS WILL HELP USHER IN A PUSH OF COLDER AIR TO INTERIOR NORCAL, ALTHOUGH COLDEST TEMPERATURES ARE ANTICIPATED THURSDAY MORNING. WHILE SOME PATCHY LOW ELEVATION FROST MAY BE POSSIBLE IN THE NORTHERN SACRAMENTO VALLEY ON WEDNESDAY, THE BREEZY WINDS WILL LIKELY DETER ANY WIDESPREAD IMPACTS. [DISC] Extended discussion (Thursday through Sunday). Moving toward the end of the week, somewhat split northwesterly flow aloft initially looks to become replaced by ridging aloft by next weekend. This will result in winds becoming lighter by Thursday, with more widespread low temperatures in the low to mid 30s by Thursday morning. As a result, some 30% to 70% probabilities of low temperatures less than 36°F are popping up across the valley/foothills for Thursday morning. There is a slight chances for additional showers from I-80 southward on Friday as a separate offshore trough moves toward Southern California, but current probabilities of exceeding 0.1 inches of precipitation are only around 20% to 40% at this time. Otherwise, with ridging expected to build in into the weekend, generally dry conditions with light to breezy diurnal/terrain driven winds accompanying the pattern. ∨ .EXTENDED DISCUSSION (THURSDAY THROUGH SUNDAY)... MOVING TOWARD THE END OF THE WEEK, SOMEWHAT SPLIT NORTHWESTERLY FLOW ALOFT INITIALLY LOOKS TO BECOME REPLACED BY RIDGING ALOFT BY NEXT WEEKEND. THIS WILL RESULT IN WINDS BECOMING LIGHTER BY THURSDAY, WITH MORE WIDESPREAD LOW TEMPERATURES IN THE LOW TO MID 30S BY THURSDAY MORNING. AS A RESULT, SOME 30% TO 70% PROBABILITIES OF LOW TEMPERATURES LESS THAN 36F ARE POPPING UP ACROSS THE VALLEY/FOOTHILLS FOR THURSDAY MORNING. THERE IS A SLIGHT CHANCES FOR ADDITIONAL SHOWERS FROM INTERSTATE 80 SOUTHWARD ON FRIDAY AS A SEPARATE OFFSHORE TROUGH MOVES TOWARD SOCAL, BUT CURRENT PROBABILITIES OF EXCEEDING 0.1 INCHES OF PRECIPITATION ARE ONLY AROUND 20% TO 40% AT THIS TIME. OTHERWISE, WITH RIDGING EXPECTED TO BUILD IN INTO THE WEEKEND, GENERALLY DRY CONDITIONS WITH LIGHT TO BREEZY DIURNAL/TERRAIN DRIVEN WINDS ACCOMPANYING THE PATTERN. [DISC] Aviation. VFR [Visual Flight Rules] conditions are mainly over interior Northern California except for isolated areas of MVFR [Marginal Visual Flight Rules]/IFR [Instrument Flight Rules] conditions in the northern Sacramento Valley and along the Sierra through 06Z [10pm PST]. After 06Z [10pm PST], more widespread MVFR [Marginal Visual Flight Rules]/IFR [Instrument Flight Rules] expected in precipitation. Southerly surface winds less than 12 knots [14 mph] become breezy up to 15 kts [17 mph] at times after 12Z [4am PST]. Periodic southwesterly gusts 15–25 knots [17–29 mph] over the Sierra. ∨ .AVIATION... VFR CONDITIONS ARE MAINLY OVER INTERIOR NORTHERN CALIFORNIA EXCEPT FOR ISOLATED AREAS OF MVFR/IFR CONDITIONS IN THE NORTHERN SACRAMENTO VALLEY AND ALONG THE SIERRA THROUGH 06Z. AFTER 06Z, MORE WIDESPREAD MVFR/IFR EXPECTED IN PRECIPITATION. SOUTHERLY SURFACE WINDS LESS THAN 12 KNOTS BECOME BREEZY UP TO 15 KTS AT TIMES AFTER 12Z. PERIODIC SOUTHWESTERLY GUSTS 15 TO 25 KNOTS OVER THE SIERRA. [AVIA] STO [Sacramento/WFO CA] Watches/Warnings/Advisories
.STO WATCHES/WARNINGS/ADVISORIES... WINTER STORM WARNING UNTIL 4 AM PST WEDNESDAY FOR WEST SLOPE NORTHERN SIERRA NEVADA-WESTERN PLUMAS COUNTY/LASSEN PARK. [WARN] |
Point Forecast Auburn CA 24 Nov 09:15pm PST Tonight A 30% chance of showers, mainly between 11pm and 4am. Mostly cloudy, with a low around 43°. ESE wind around 5 mph. Monday Showers, mainly after noon. High near 51°. SSE wind around 7 mph. Chance of precipitation is 90%. New precipitation amounts between a tenth and quarter of an inch possible. Monday Night Showers. Steady temperature around 50°. South wind around 6 mph. Chance of precipitation is 100%. New precipitation amounts between a quarter and half of an inch possible. Tuesday Showers likely. Mostly cloudy, with a high near 51°. South wind around 5 mph. Chance of precipitation is 70%. New precipitation amounts between a tenth and quarter of an inch possible. Tuesday Night A 40% chance of showers, mainly before 4am. Mostly cloudy, with a low around 37°. Light NE wind. Wednesday A 20% chance of showers before 10am. Sunny, with a high near 54°. Wednesday Night Mostly clear, with a low around 37°. Thanksgiving Day Mostly sunny, with a high near 54°. Thursday Night A slight chance of showers after 10pm. Partly cloudy, with a low around 41°. Friday A slight chance of showers. Mostly sunny, with a high near 56°. Friday Night Partly cloudy, with a low around 41°. Saturday Mostly sunny, with a high near 57°. Saturday Night Partly cloudy, with a low around 42°. Sunday Mostly sunny, with a high near 57°. Tonight A 30 percent chance of showers, mainly between 11pm and 4am. Mostly cloudy, with a low around 43. East southeast wind around 5 mph. Monday Showers, mainly after noon. High near 51. South southeast wind around 7 mph. Chance of precipitation is 90%. New precipitation amounts between a tenth and quarter of an inch possible. Monday Night Showers. Steady temperature around 50. South wind around 6 mph. Chance of precipitation is 100%. New precipitation amounts between a quarter and half of an inch possible. Tuesday Showers likely. Mostly cloudy, with a high near 51. South wind around 5 mph. Chance of precipitation is 70%. New precipitation amounts between a tenth and quarter of an inch possible. Tuesday Night A 40 percent chance of showers, mainly before 4am. Mostly cloudy, with a low around 37. Light northeast wind. Wednesday A 20 percent chance of showers before 10am. Sunny, with a high near 54. Wednesday Night Mostly clear, with a low around 37. Thanksgiving Day Mostly sunny, with a high near 54. Thursday Night A slight chance of showers after 10pm. Partly cloudy, with a low around 41. Friday A slight chance of showers. Mostly sunny, with a high near 56. Friday Night Partly cloudy, with a low around 41. Saturday Mostly sunny, with a high near 57. Saturday Night Partly cloudy, with a low around 42. Sunday Mostly sunny, with a high near 57. |
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