####018008388#### FXUS66 KMTR 130445 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 845 PM PST Fri Dec 12 2025 ...New UPDATE, MARINE... .KEY MESSAGES... Updated at 1248 PM PST Fri Dec 12 2025 - Hazardous beach conditions through the evening - Impacts from Tule Fog continue in the North Bay and interior East Bay valleys - Wetter conditions expected next week && .UPDATE... Issued at 844 PM PST Fri Dec 12 2025 Tule Fog and radiational fog have begun to develop and spread across larger areas of the North Bay interior valleys and East Bay interior valleys. A Dense Fog Advisory has been issued until 11 AM Saturday morning. Please use caution if traveling in these areas tonight and Saturday morning. Don't use your high beams, give yourself extra time and extra distance between vehicles. Most locations that saw fog last night and this morning will see similar conditions tonight and tomorrow morning. The Beach Hazards Statement will be allowed to expire at 10 PM tonight with diminishing seas through the weekend. && .SHORT TERM... Issued at 1248 PM PST Fri Dec 12 2025 (This evening through Saturday) Persistent stratus and fog continues across the valleys of the North Bay and interior East Bay, with the clouds continuing to mix out throughout the afternoon and into the early evening hours, when the Tule Fog outgrowth returns to the Bay Area. To the south, a southerly surge is developing to the west of San Luis Obispo County, and will travel northwards along the Big Sur coast, flow into the Monterey Bay region, and progress along the San Mateo coast through the evening and overnight hours. Continuing to opt for a more persistent forecast for high temperatures today, with highs in the Central Coast valleys reaching the lower to middle 70s, the Bay Area valleys reaching the upper 50s to lower 60s barring the northern and eastern parts of the interior East Bay, where highs reach the middle 40s to near 50, and highs across the higher elevations into the lower to middle 70s. Overnight, expect lows in the upper 30s to middle 40s for the valley regions, and the middle 40s to the lower 50s in the higher elevations. Dense Fog Advisories may need to be issued early Saturday morning for the inland valleys, but also the immediate coast depending on the evolution of the Tule Fog and southerly surge through the next day. By Saturday, the ridge that has brought us the last few days of stable conditions will begin move off to the east, with the coastal stratus retreating to the immediate coastal region. How the Tule Fog will react to the change isn't all too clear. The current forecast shows a similar clearing pattern to today's. High temperatures are currently expected to remain nearly the same as today's in the lower elevations, perhaps a couple of degrees cooler in the higher elevations. && .LONG TERM... Issued at 1248 PM PST Fri Dec 12 2025 (Saturday night through next Thursday) As we head into the early part of next week, the ridge continues to move to the east and a pattern change brings more zonal flow to the region by Tuesday. This new pattern should help scour out the Tule Fog and, when combined with a plume of moisture with PWAT values up to 1.2 inches, brings a chance of light rain to the region Tuesday and Wednesday, focused on the North Bay. A weak ridge will move through the state on Thursday and Friday, but the overall flow should remain generally zonal and lingering showers and drizzle are possible from remnant moisture in the region. Beyond the 7-day outlook, the forecast points towards another round of wet weather across the region for the weekend of the 20th and 21st as a deep trough in the eastern Pacific coincides with another plume of moisture moving through the West Coast. The CPC outlooks are leaning towards precipitation totals above the seasonal average in their latest 6-10 day outlooks (from December 18th to the 22nd, 55-70% probability), giving the region a moderate chance for heavy rain and high winds (40-60% probability of total rainfall and sustained winds reaching the 85th percentile of the seasonal distribution) starting on the 20th. For context, when taking the long-term averages, December is the wettest month for downtown San Francisco with monthly average precipitation of 4.76 inches. We have not seen a drop of rain since the 20th of November, and for the 6-10 day outlook, the expected rainfall total lies somewhere around three quarters of an inch of rain. The chances for rain don't stop that weekend: CPC outlooks maintain the lean towards precipitation totals above seasonal averages in the 8-14 day outlook (December 20th-26th, seasonal average of over an inch of rainfall at downtown San Francisco), the moderate chances for heavy rain and high winds mentioned earlier in this paragraph extend through the 26th, and the ensemble mean products suggest a lingering trough in the eastern Pacific through this period, a pretty notable signal especially this far out into the forecast. && .AVIATION... (00Z TAFS) Issued at 332 PM PST Fri Dec 12 2025 Currently VFR but fog and stratus remain entrenched along the Delta and in portions of the interior East Bay. Kept the timing of fog returning to STS, APC, LVK, and SJC about the same as the last night following a persistence forecast. The one thing to watch for is that more expansive fog cover across the East Bay tonight than at this time last night may result in a slightly faster arrival time of fog to LVK and SJC. For coastal sites HAF, MRY, and SNS, a southerly surge of marine stratus will bring a return of IFR-LIFR conditions overnight. This is likely to at least temporarily bring fog to MRY and SNS. Winds generally stay light through the TAF period but maintained some gustier conditions at APC given the similar setup tonight compared to last night. Vicinity of SFO...VFR. Not expecting Tule Fog to reach SFO tonight. The one question would be if low clouds from the southerly surge will be able to reach SFO by mid to late tomorrow morning. Forecaster is leaning more towards the HREF which supports SFO staying VFR through tomorrow morning but suggests clouds will return by late tomorrow evening, at the end of or just after the end of the current TAF period. Winds generally remain light and offshore through the TAF period with periods of more variable winds overnight. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...VFR becoming IFR-LIFR as a southerly surge arrives bringing low clouds and fog. Confidence is slightly higher that fog will impact SNS than MRY but there is some potential for both to at least temporarily see fog tomorrow morning. LAMP guidance leans on the side of MVFR-IFR conditions at MRY but there is still a low chance of LIFR conditions developing. Winds remain light at MRY through the TAF period. Moderate SE drainage winds develop at SNS overnight with light NNW to N winds otherwise expected. && .MARINE... (Tonight through next Thursday) Issued at 844 PM PST Fri Dec 12 2025 Dense fog is possible across the southern coastal waters tonight as a southerly surge of marine stratus moves northward. Gentle northeasterly winds will gradually shift southerly on Saturday morning before moderate northerly winds return again on Monday. Seas continue to subside with slight waves continuing through the weekend. Unsettled weather returns by the middle of next week with seas to build and light rain possible across the coastal waters. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...Beach Hazards Statement until 10 PM PST this evening for CAZ006- 505-509-529-530. Dense Fog Advisory until 11 AM PST Saturday for CAZ506-510. PZ...None. && $$ SHORT TERM...DialH LONG TERM....DialH AVIATION...Kennedy MARINE...Kennedy Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, X, and YouTube at: www.facebook.com/nwsbayarea x.com/nwsbayarea www.youtube.com/nwsbayarea ####018003834#### FXUS63 KDMX 130446 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 1046 PM CST Fri Dec 12 2025 ...Updated for the 06z Aviation Discussion... .KEY MESSAGES... - Winter Weather Advisory for 1 to 4" of snow Saturday. Locally higher amounts possible. - Cold Weather Advisory follows Saturday night and Sunday morning. Wind chills as low as -30 expected north. - Mild weather builds in the first half of the work week. && .DISCUSSION... Issued at 229 PM CST Fri Dec 12 2025 A thermal front has moved across the state today and temperatures were starting to slide into the teens in northwest Iowa. Precipitation was sparse along the front, with most of it closer to the parent low to the northeast of the state. Midlevel cloudiness will replace the low level stratus at least for a time tonight. The last gasp of energy along the northwest flow pattern arrives tonight. A notable change has been a warming of the midlevels compared to yesterday, taking some of the profile out of the DGZ. This is due to the strong downslope flow with wind speeds up to around 70kts. This reduces the SLRs below 20:1, increasing confidence in snowfall amounts remaining under 4 inches for much of the Advisory area. There will be locally higher amounts embedded as the weak fgen band generates lift in the DGZ. Omega values generally remain below -5, but midlevel Q vectors intensify as the clipper reaches southeast Iowa, increasing synoptic forcing. Some ice pellets could mix in on the southwest flank of the snow as ice introduction aloft is lost, but the drops will fall towards the cold low-levels, causing freezing before they reach the surface. Temperatures plummet as clouds are pulled away and an arctic high approaches. Cold northwest flow will drop temperatures below zero statewide. There will be a window of wind chills as low as -30 degrees in the north, the window for this being short due to the high settling overhead, calming winds. A Cold Weather Advisory was issued for Saturday night/Sunday morning to reflect when these dangerous wind chill values will occur. An upper level ridge will break this stagnant northwest flow pattern in the early week. Temperatures over 40 degrees will work to erode the snowpack. Flow will switch to zonal during the second half of the week which will open up the chance for a more active pattern with the Pacific moisture in play. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1042 PM CST Fri Dec 12 2025 Ceilings are expected to lower from northwest to southeast through the morning as the next system arrives into Iowa. This will bring light to moderate snow across the state through the morning, peaking between sunrise through 18z across the majority of terminals, and less so at KMCW, before gradually tapering off through the afternoon. MVFR/IFR conditions are expected during this time due to the lowered ceilings as well as for reduced vsbys from the snow. Exact timing and impacts are expected to be tweaked further over the next several hours as the event unfolds. Otherwise, winds gusting up to 15 knots into the afternoon could blow some of this fresh snow around at times leading to possible lingering restrictions. && .DMX WATCHES/WARNINGS/ADVISORIES... Cold Weather Advisory from 6 PM Saturday to 10 AM CST Sunday for IAZ004>007-015>017-023>028-033>039-045>050-059>062-073>075- 084>086-095>097. Winter Weather Advisory until 3 PM CST Saturday for IAZ023- 033>036-044>048-058>060. Winter Weather Advisory from 3 AM to 3 PM CST Saturday for IAZ049-061-062-073>075-085-086-097. && $$ DISCUSSION...Jimenez AVIATION...Bury ####018006640#### FXUS63 KAPX 130449 AFDAPX Area Forecast Discussion National Weather Service Gaylord MI 1149 PM EST Fri Dec 12 2025 .KEY MESSAGES... - Widespread light to moderate snow this evening and tonight with heavy lake enhanced snow over parts of NW lower, eastern upper, and near the tip of the mitt - Long duration lake effect snow and cold temperatures this weekend will lead to hazardous travel conditions for areas of northern lower and eastern upper. Wind chill values will struggle to reach above 0F Saturday - Chances for snow continue Monday as another system passes over northern MI - Temperatures begin to warm Tuesday with precipitation chances continuing next week && .SHORT TERM /THROUGH SATURDAY/... Issued at 210 PM EST Fri Dec 12 2025 Currently, surface observations place a stronger cold front near the MN/WI border. Surface gradients have been increasing this afternoon, leading to strengthening southwest winds over Lake MI and northern MI. Radar is hinting at some light snow showers forming just off the coast of Charlevoix and moving into Emmet Co. Tonight: An approaching system will continue to spread light to moderate snow over northern lower and eastern upper this evening. Stronger winds aloft and the tighter surface pressure gradient will continue to strengthen winds as they veer westerly. This "punch" of colder air will encompass northern MI by early Saturday morning. Times of moderate and heavy snowfall will be seen initially along the snowbelts, tip of the mitt, northern Lake MI coast, and areas of eastern upper late this evening and tonight. The stronger west to west-northwest winds and colder air during this time will result in powder like snow. This snow has slightly lower SLRs (still a dry snow), but is so fine that visibilities are greatly reduced when it blows around. Peak snowfall intensity is seen early Saturday for much of NW lower as snow transitions to more of a lake effect footprint, and will continue through the day. Saturday: Snowfall will become more confined to the northern section of the NW lower snowbelt as winds remain west-northwest. A band of focused snow could form near Little Traverse Bay, resulting in the potential for Emmet and Cheboygan counties to see spots of heavy snow through much of Saturday. Intensity of snowfall over the southern part of NW lower will weaken, but snow should persist. Around 2 to 6" is expected over the advised areas of northern lower by late Saturday, with locally higher amounts up to +8". Over eastern upper, heavy snow will likely be confined to northern Chippewa (Whitefish Point and the SOO), with light to moderate times of snow meandering into other parts of Chippewa. Bands of heavier lake effect snow will begin early Saturday and linger for much of the day, resulting in accumulations of 4 to 8 inches with locally higher amounts of +10" near Whitefish point and near the SOO. Although the snow characteristic will be more of a powder, an ideal environment and some synoptic help will allow for times of snowfall rates of 1-2" per hour under the heavier bands. Gusty winds and cold temperatures will be present for most of northern MI Saturday, resulting in areas of blowing snow and wind chill values that struggle to rise above 0F the whole day. See the latest winter weather products for more details. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... Issued at 210 PM EST Fri Dec 12 2025 Late Saturday into Sunday, the upper closed low amplifies west to east and rotates southward over the area. This helps push the final slug of cold air southward. Winds over the CAN shield will turn north-northeast early Sunday. As they do, established lake aggregate troughing over NE Lk Superior will shift over the Whitefish Bay. With this, heavy snow could be pointed right at the SOO, leading to a 3-6 hour window of 1-2" per hour rates. There is still some uncertainty with the exact time this will occur - Saturday evening or more Saturday night; however the potential remains high for total snow accumulations (Sat & Sun) to reach +8" near the SOO. This will also be a night of very cold temperatures, especially for spots that can see clearer skies overnight (parts of NE lower). During the day Sunday, winds will veer north and weaken. Potential exists for some areas of LL convergence near Grand Traverse Bay, which could keep areas near, south and west of Grad Traverse Bay snowy most of Sunday. Another system quickly approaches the area Monday, returning southwest winds and snow chances to most of eastern upper and parts of northern lower. Some brief lake effect snow will be seen late Monday as the system passes. The focus of snow amounts for this system looks to be eastern upper at this time. Tuesday thru end of period: Temperatures begin to warm Tuesday with breezy southwest winds. Precipitation chances continue for eastern upper late Tuesday into Wednesday, likely in the form of snow up there. Temperatures will warm above freezing beginning mid week, with multiple rounds of precipitation next week as temperatures remain relatively mild. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1141 PM EST Fri Dec 12 2025 Lake effect snow will continue to organize through early this morning, with the primary target area centering between taf locations into the northwest lower Michigan snow belts through today. Still expecting to see some lighter snow showers and areas of lower cigs at the taf locations, but thinking vast majority of this time will remain MVFR to lower end VFR. West winds will remain gusty (up and over 25 knots at times), producing some blowing and drifting snow as well. Winds veer northwest this evening, focusing bands of snow across the western taf locations...likely producing periods of IFR conditions. && .APX WATCHES/WARNINGS/ADVISORIES... MI...Winter Weather Advisory until 7 PM EST Saturday for MIZ016-017- 020>022-025>028-031-032-099. Winter Storm Warning until 10 PM EST Saturday for MIZ086-087. MARINE...Small Craft Advisory until 7 PM EST Saturday for LHZ345>349. Small Craft Advisory until 7 PM EST Saturday for LMZ323-341- 342-344>346. Small Craft Advisory until 7 PM EST Saturday for LSZ321-322. && $$ SHORT TERM...ELD LONG TERM...ELD AVIATION...MSB ####018005508#### FXUS63 KFSD 130449 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 1049 PM CST Fri Dec 12 2025 .KEY MESSAGES... - Patchy blowing and falling snow may reduce visibilities through the early evening hours, so use extra caution on the roads during the evening commute. - Another round of snow moves in late tonight and continues into tomorrow morning. 2-4" of snow is expected mainly near and south of I-90, with a low-to-medium chance (20-50%) of a few spots seeing greater than 4 inches of snow. - An influx of arctic air over the weekend will lead to cold temperatures and even colder winds chills especially by Sunday morning. Wind chill values as low as -30 degrees are expected. - Quieter conditions return by next week with a shift towards milder temperatures by midweek. && .DISCUSSION... Issued at 248 PM CST Fri Dec 12 2025 It's been a cold and breezy day on our Friday as temperatures have fallen throughout the day. We are currently sitting in the single digits to low 10s above zero, but wind chills are below zero for most of the area. Winds have been able to blow the fresh snow pack around, and additional light snow has reduced visibilities from time to time today. This will continue for the next few hours, so continue to use extra caution on the roads. Falling snow and winds will diminish this evening, but the break from falling snow will be short-lived as our next winter system is set to move in around midnight tonight, which we'll discuss below. After some lingering light snow this evening over south-central South Dakota, a new band of snow will develop and move into our area west of the James River around midnight and quickly expand southeastward. The band of snow will intensify a bit around daybreak and then exit off to our south and east around noon. So a quick-moving system, but will have rates up to 0.75" an hour leading to a stripe of 2-4" of snow across parts of the area when all said and done. The favored areas for this stripe for these amounts will be near and south of I-90. Can't rule out an even narrower band of 4-6" somewhere within the general 2-4", but guidance today has become less excited on the potential for 4+ inches. Currently, the chance of at least 4 inches of snow or greater is around 20-50%, with the chance of at least 6 inches now less than 20%. The chance of 1" per hour snowfall rates have also come down a bit according to the 12z HREF compared to the run last night. For areas north of I-90, amounts look to drop of quickly from south to north, but overall the current Winter Weather Advisory remains in good shape. Attention then turns to the colder weather that will move in after the snow. Wind chills are set to drop to as low as 30 degrees below zero Saturday night into Sunday morning, and for that reason, a Cold Weather Advisory has been issued for all of southwest Minnesota, most of northwest Iowa, and a large part of east-central South Dakota. Winds will be fairly light Saturday night, but with air temperatures dropping to the teens below zero within the Cold Weather Advisory, any light wind will result in these dangerously cold wind chills through much of Sunday morning. From here, temperatures will warm-up fairly quickly, with highs by Sunday afternoon in the teens and 20s above zero. After another cold night Sunday night, temperatures warm-up further into Monday as highs then look to climb near the freezing mark. Tuesday and Wednesday will be the warmest days next week, with highs in the 30s and 40s. Temperatures will be knocked back down a peg Wednesday night into Thursday, but it won't get nearly as cold as what we'll see this weekend. In fact, temperatures will be overall seasonal to close out the next work week. A quieter pattern also sets up, with only small rain chances north of I-90 late Wednesday into early Thursday at this time. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1046 PM CST Fri Dec 12 2025 MVFR stratus and the next round of snow are still expected to move into the area overnight, moving southeast through the morning and early afternoon hours. Beginning to see some light returns on radar as well as some snow on the DOT cameras across south central SD. Once VFR conditions deteriorate, we should remain MVFR to IFR with the snow. MVFR stratus may linger through the late afternoon, with some improvements and return to VFR through the evening hours. Northerly winds remain light through much of the period, with gusts around 20 knots during the afternoon. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...Winter Weather Advisory until noon CST Saturday for SDZ038-050- 052>054-057>071. Cold Weather Advisory from 6 PM Saturday to 10 AM CST Sunday for SDZ038>040-053>056-059>062-065>067. MN...Cold Weather Advisory from 6 PM Saturday to 10 AM CST Sunday for MNZ071-072-080-081-089-090-097-098. IA...Winter Weather Advisory until noon CST Saturday for IAZ001-012- 013-020>022-031-032. Cold Weather Advisory from 6 PM Saturday to 10 AM CST Sunday for IAZ001>003-012>014-021-022-032. NE...Winter Weather Advisory until noon CST Saturday for NEZ013-014. && $$ DISCUSSION...Samet AVIATION...SG