Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/22/24


Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
906 PM CST Thu Nov 21 2024 .KEY MESSAGES... - Patchy fog is possible tonight. - Fresh snow cover could cause overnight low temperatures to fall into the single digits tonight. Otherwise, temperatures Friday and Friday night should be close to normal. - There is a 15 to 25% chance of light snow over portions of north central and northeastern SD into west central MN Sunday through late Sunday night. Little to no accumulation is expected. - Average to slightly below average temperatures this weekend and around 5 to 10 degrees below average early next week. && .UPDATE... Issued at 905 PM CST Thu Nov 21 2024 Current forecast is on track, therefore no changes made at this time. && .SHORT TERM /THIS EVENING THROUGH FRIDAY NIGHT/... Issued at 117 PM CST Thu Nov 21 2024 At 1 PM CST, other than overcast skies on the Prairie Coteau and west central Minnesota, the CWA is basically sunny or mostly sunny with some higher level clouds streaming by. Temperatures under the cloudy skies are in the upper teens to mid 20s (also the area with the most snowfall the other day), while sunny sky areas were warming through the 20s into the low 30s. Winds were northwest at 5 to 15 mph, with some areas east in the CWA gusting to around 25 mph at times. Surface high pressure is over the Missouri River valley region of the CWA. It is forecast to re-align along the Dakotas border with Minnesota by 12Z Friday. If the clouds over the eastern zones dissipate or continue their move off into Minnesota, the portion of the CWA that received 2in to 5-6in of snow Tuesday night into Wednesday could be staring a clear sky/light wind night square in the face; meaning there is the potential for low temperatures over this new snowfield to bottom out a good 5 to 10 degrees (or more) lower than surrounding bare ground areas. Have attempted to draw in that potential some in the min T forecast grid, while maintaining bordering CWA integrity with neighbors. There could also be some fog on/near this snow field later tonight as winds go light and temp/dewpoint depressions narrow to just a degree or two at the surface. Also worth noting, the HREF skycover guidance is hinting that the scattered coverage higher-level cloudiness happening now will be ongoing overnight, which could end up pumping the breaks on snowfield ultra-cold low temperatures, and on fog development. During the day on Friday, there is an attempt made for low level WAA over the CWA, in particular across the western third of forecast zones (Missouri River valley region), in response to lee of the Rockies/Black Hills surface pressure falls. So, fully expecting high temperatures to warm into (at least) the low to mid 40s across much of central and north central South Dakota. Something to watch, though, is how far south into the CWA a shallow cold airmass can push Friday night. The latest RAP output shows a cold front beginning to work into Corson County by 00Z Saturday, potentially reaching as far south as a line from Pierre to Miller to Watertown to near Appleton, MN by 12Z Saturday. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Issued at 117 PM CST Thu Nov 21 2024 Starting out the long term on Saturday, models are consistent on a ridge overhead with zonal winds turning southwesterly. Just west of the ridge, the low continues to spin off the coast of WA/OR with a trough, south of this low, extending over the Pacific Ocean. The ridge overhead will slide eastward with a negative shortwave forming over southern Alberta/Saskatchewan/northern MT along with several embedded shortwaves/pulses over the Rockies Saturday evening. At the surface, an elongated area of low pressure will form over this area, pushing east/southeast with the broad surface low extending from the Northern Plains southward through Texas by 12Z Sunday. The low then track east/northeast Sunday into Monday with the upper level waves following behind. Models keep most of the precip along the ND/Canadian border Saturday night through Sunday (closer to the 700-850mb low skirting east within this wave). However, ENS brings the chance of precip a bit further south, brushing our northern/northeastern CWA Sunday through early Monday as it indicates the wave aloft plunging further south than GEPS/GEFS. NBM does a good job indicating this with pops of 15- 25%, highest along the ND/SD border, with Ptype being mainly snow. EC meteograms do indicate a 10-15% chance that ptype could be light freezing rain/drizzle at 8D3 and less than 10% chance at KATY mixed in with the snow early Sunday. EC soundings at 8D3/KATY shows a potential warm nose (and dry air above this) with GEFS soundings for these locations keeps the column at or below freezing indicating all snow (which GEFS plumes do indicate). Low confidence exists on this potential as of now. No ice accumulation expected with little to no snow accumulations. Otherwise, behind the system, high pressure moves in and will be the dominant weather pattern through the midweek, keeping the area dry and quiet. Aloft, winds will mainly be zonal through the midweek as models indicate a broad positive tilted trough moving west to east over the CONUS with lots of variability between the models on track and intensity and whether it the pattern remains phased together or becomes split flow. Both EC/GEFS do hint at a possible lee low forming near CO/OK/TX area Wednesday and tracking northeast through end of next week. Depending on track this may bring the return of snow (under 20% chance for now). Confidence is low this far out on the overall pattern and where/if precip will fall and where. Temps will be around average to a few degrees below average for the weekend. As that high moves in early next week, it will bring in colder air with it with 850mb temps ranging to the single digits below zero to -11C with the coldest air over the northern CWA with GEFS being the most aggressive on this colder air. Temps are forecasted to run about 5 to 10 degrees below average. Even colder air is forecasted to move in for the end of the week (again GEFS being the most aggressive) with 850mb temps ranging from -10 to -13C by early Saturday morning with this colder air hanging around at least through the early following week. Latest NBM has a 30 to 60% chance of low temperatures below zero by Sunday morning (12/1) and 30-55% chance Monday morning (12/2). CPC highlights this well with a slight risk (20%) of "Much Below Normal Temperatures" 11/28-12/4 and a moderate (40% chance) over the north central CWA 11/28-11/30. && .AVIATION /00Z TAFS THROUGH 00Z FRIDAY/... Issued at 525 PM CST Thu Nov 21 2024 Terminals KABR,KATY,KPIR,KMBG For the most part, VFR conditions will prevail across the area tonight and through the day Friday. The exception will be across far eastern parts of the area where some patchy fog and MVFR cigs may develop late tonight into Friday morning. KATY may be affected. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...Parkin SHORT TERM...Dorn LONG TERM...MMM AVIATION...Parkin
Area Forecast Discussion
National Weather Service La Crosse WI
548 PM CST Thu Nov 21 2024 .KEY MESSAGES... - Diminishing winds and areas of rain this afternoon will give way to a small chance (20%) of drizzle developing into tonight. Temperatures should largely stay above freezing to mitigate the threat of freezing drizzle. - Active weather returns early next week with generally low to medium (20 to 50%) chances for minor amounts of snow with a couple systems Monday through Thanksgiving Day. Could be minor impacts to holiday travel. - Slight warming trend into this weekend, then below normal temperatures next week. && .DISCUSSION... Issued at 214 PM CST Thu Nov 21 2024 Diminishing winds and drizzle potential into tonight: Broad occluded cyclone continues to slowly depart through the Great Lakes region. Lingering snow impacting portions of central and southwest Wisconsin since last night switched to all rain by midday as temperatures continue to climb into the upper 30s to lower 40s. Winds have been gusty behind this departing system with gusts commonly in the 30 to 40 mph range. Gusts higher than that have been few and far between, so have canceled the wind advisory for southwest Wisconsin and Clayton County early. The pronounced trowal with this occluded system continues to wrap around back through the Mississippi River valley this afternoon, bringing a tongue of increasing low level moisture into the local area. Forecast soundings show increasing depth of low level saturation through this afternoon, especially along and east of the Mississippi River. While synoptic scale forcing will gradually weaken heading into this evening, the RAP shows a 700-600mb band of frontogenesis developing over the region which may interact with the 1+ km deep low level saturation to produce areas of drizzle. This is hinted at by some high resolution composite reflectivity guidance, such as the NamNest and the HRRR. While confidence is low to medium in drizzle potential, it does look to be more favored where minimum temperatures tonight will be at or above freezing. Will have to keep an eye on trends this evening, but currently not anticipating potential for freezing drizzle. Active, colder weather early next week for pre-holiday travel: A drier airmass and upper level ridging will bring a break from the breezy/windy conditions and active weather Friday through the weekend. The next system makes landfall on the West Coast early Saturday, with the wave(s) traversing the northern US and southern Canada and eventually reaching the Upper Midwest by late Sunday. Whether this arrives as a singular, stronger wave (riding the US/Canada border) or 2 weaker split waves remains in question, but there is ensemble agreement for some light snow potential locally. There is about a 40 to 60% probability for at least measurable snow (0.1") north of I-90, but only a 20% or less chance for 1" or more. Somewhat active weather is expected to continue in the busy pre- Thanksgiving travel days early next week. However, there are few overall forecast details to hang one`s hat on at this time, and ensemble guidance is split on snow potential that far out. ENS probabilities suggest around 40% for 1" or more of snow late Wednesday into Thanksgiving Day while GEFS is closer to 10%. There is more confidence in the temperature pattern dropping below normal by Monday, staying chilly through at least Thanksgiving Day. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 548 PM CST Thu Nov 21 2024 Main aviation concerns this evening continue to revolve around winds and low ceilings across the forecast area. Gusty winds should continue to diminish through the night tonight, remaining from the north/northwest through the period. What looks to stick around is the low stratus currently across the area, with MVFR to IFR cigs forecast. There is some variability between the different models, but there does remain some signal for a few pockets of LIFR to develop late tonight/early Friday morning (mainly across SE MN). Have maintained the previous mention this issuance, but will continue to monitor trends this evening. Otherwise, guidance would suggest ceilings will be slow to improve on Friday, so have continued to trend that way. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...Kurz AVIATION...EMS
Area Forecast Discussion
National Weather Service Burlington VT
1014 PM EST Thu Nov 21 2024 .SYNOPSIS... A long duration rain event with mountain snow showers is currently underway with rain and snow likely to linger through the weekend. This beneficial rainfall comes after a prolonged dry spell and is welcomed as no impacts are expected from this system. A brief break in precipitation is expected Friday afternoon but otherwise we will remain showery and cool through the upcoming weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 1001 PM EST Thursday...We have increased southeasterly downslope winds from Rutland County northward along the western Slopes of the Green Mountains for the 10-14Z time frame Friday. The secondary surface low southeast of Long Island lifts northward overnight, and is associated with an intensifying 850mb easterly jet. Don`t think we`ll see full mixing based on low-level stability profiles, but gusts up to 40 mph are likely for an hour or two around daybreak based on latest HRRR and 00Z NAM3. We`ll continue to monitor in the event the low-level jet strengthens more than currently expected. Also seeing melting layer drop to between 1500-2000ft based on KCXX radar, and that`s about where it should remain through the remainder of the overnight. A slushy 1-2" snow accumulation is expected in the 1500-2000ft elevational band with some evidence of accumulation on higher elevation roads, especially in the northern Adirondacks. Higher snowfall totals will occur about 2000ft with subfreezing temperatures, especially in the northern Adirondacks. The high peaks of the Adirondacks should see an additional 4-8" overnight at summit level, but again, just wet conditions for the majority of motorists across the region except for the highest elevation roadways. Previous discussion follows. Previous Discussion...We continue to see a complex storm system impacting the northeastern US this afternoon with widespread rainfall and mountain snow showers impacting Vermont and northern New York. Presently, an anomalously strong upper level low is situated across the Ohio River Valley with a surface low displaced to the southwest of the upper low center. In addition, we have begun to observe a new double barrel low pressure system developing near Benchmark. The strong upper low to the west has cut off the supply of cold air and have funneled the coldest air across central and southern New York where the bulk of snowfall has been seen thus far. The coastal low is actually helping to keep the warmer air locked into the region as we see the onset of increasing easterly flow off the western Atlantic. The precipitation currently overspreading the region is tied to a frontal occlusion attached the surface low well to our west. Temperatures aloft are cooling slightly from a combination of the wet-bulb effect and very subtle cold air advection. Webcams have shown that Whiteface Mountain and Killington have both switched over to snow with temperatures between 28 and 30 degrees. Other summit sites remain between 33 and 35 degrees but those too will be dropping shortly as precipitation continues to fall through dry air and cools off the surface. As you head down below 4000 ft, we have seen just plain rain as temperatures continue to hover in the upper 30s to mid 40s. Rainfall thus far has ranged from just a few hundreths across northeastern Vermont all the way to three tenths of an inch across the St. Lawrence Valley. Basically, everything remains on track from the previous forecast. Models have come into much better agreement showing that warm air will remain entrenched in the lower elevations, especially tonight and much of Friday to where we have continued to fine tune our snow level grids. For tonight, we expect snow levels to drop to about 2500 feet across northern New York but will remain at or above 3800 ft across Vermont. && .SHORT TERM /SATURDAY THROUGH SUNDAY/... As of 240 PM EST Thursday...Cold air will finally begin wrapping into Vermont Friday afternoon and evening as the upper level low moves into western Massachusetts/western Connecticut. However, the colder air will likely coincide with a noticeable dry slot where the majority of the late morning through early evening hours will have very little, if any, precipitation falling across the region. Winds during this time about 1000 ft will be easterly given the position of the upper low which would favor some downslope conditions along the western slopes and upslope across the eastern facing slopes. As both the coastal low and surface low shift further offshore late Friday night into Saturday morning, we will see wind shift back to a more climatological northwest direction which will then begin the upslope machine. Precipitation isn`t likely to be heavy Saturday or Sunday but with continued upslope flow, we could easily see 1-2 inches of accumulation every 6 hours along the western slopes that will add up over time. Snow levels on Saturday will drop to 1800 to 2200 feet which will allow for some mid-mountain snow accumulations but most of the population centers for the North Country will continue to see rain showers while the mountains get in on all the snow action. We will see snow levels drop to 1200 feet Saturday night which may allow for some very minor accumulations to occur along the foothills of the Green Mountains but any accumulations will remain well under an inch. && .LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/... As of 240 PM EST Thursday...Vertically stacked low pressure will be moving away into the Canadian Maritimes on Sunday, leaving northwesterly flow and orographically enhanced showers in its wake, mainly in the morning hours before precipitation tapers off in the afternoon. Snow levels will sit at about 1,000 to 2,000 feet elevation. Everywhere below 1,000 feet is expected to see only rain showers. Additional rainfall amounts of up to 0.20" are possible in terrain areas, especially the Greens, while additional snowfall of up to about 3 inches is possible above 2000 feet elevation. Northwesterly wind gusts could reach up to 15-30 knots off the departing low, perhaps up to 40 knots at the peaks and in downsloping gusts on eastern slopes of the mountains. Highs Sunday will be seasonable in the upper 30s to upper 40s, but may feel much chillier (mid 20s to upper 30s) due to the wind. Gusty winds will taper off a bit into the overnight hours on Sunday, but remain at about 10-25 knots. Temperatures will fall into the 20s and lower 30s overnight Sunday into early Monday, and precipitation will finally come to a complete end by then. There will be brief ridging and a break from precip on Monday before another trough arrives Monday night/Tuesday with associated surface low and occluding frontal boundary. Highs Monday and Tuesday will be mild in the 40s during this period thanks to the brief ridging and then influx of milder air with the system. This will raise snow levels to above 3000 feet and produce mostly rain on Monday night before cold air advection follows on Tuesday and snow levels could plummet to 1000 feet again, allowing snow to mix in at these elevations and higher before the system moves out Tuesday night. There`s the potential at the onset of this system for some freezing rain type precipitation to occur as model soundings produce a warm nose, but it`s too soon to set any details on p-type in stone. Cold air advection following the system could keep snow showers lingering at high elevations into Wednesday. After this, models diverge on the timing and placement of the next wave to come through the forecast area late next week. Overnight lows are expected to take a plunge into the teens to mid 20s by Thursday night. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... Through 00Z Saturday...Generally a mix of MVFR and IFR conditions areawide overnight along with periods of rain. Did include a rain/snow mix after 03Z at KSLK, but with sfc temperatures remaining slightly above freezing, shouldn`t be of significant impact for aviation ground operations at KSLK. Appears precipitation will become lighter during the late morning and afternoon hours on Friday, and may even see a return to VFR ceilings for a time Friday afternoon as mid-level dry slot moves in from the east. Winds are light out of the north and northeast early this evening. However, winds will be increasing and becoming gusty during the pre-dawn into the daylight hours on Friday as they shift NE and E. Strongest winds will be at the KRUT TAF sites, possibly reaching 35kts around 10Z Friday. LLWS is expected to dominate sites outside of the wider valleys as easterly winds pick up over parts of Vermont and increase at 2000 ft agl up to 40 to 45 knots. LLWS is a concern mainly for SLK, RUT, MPV, and EFK. Most likely timing for LLWS will be from 09Z to 18Z Friday. Outlook... Friday Night: Mainly VFR, with local IFR possible. Chance SHRA. Saturday: Mainly MVFR, with areas IFR possible. Chance SHRA. Saturday Night: Mainly MVFR, with local IFR possible. Likely SHRA, Definite SHSN. Sunday: Mainly MVFR, with areas VFR possible. Chance SHRA, Chance SHSN. Sunday Night: Mainly VFR, with local MVFR possible. NO SIG WX. Monday: Mainly VFR, with areas MVFR possible. NO SIG WX. Monday Night: Mainly VFR, with local MVFR and IFR possible. Chance SHRA, Likely SHSN. Tuesday: Mainly MVFR, with areas IFR possible. Likely SHRA. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Clay NEAR TERM...Banacos/Clay SHORT TERM...Clay LONG TERM...Storm AVIATION...Banacos
Area Forecast Discussion
National Weather Service Dodge City KS
517 PM CST Thu Nov 21 2024 .KEY MESSAGES... - Mild afternoon temperatures Friday, Saturday, and Sunday as upper level high pressure builds across western Kansas. Highs each day in the lower 60s likely (>60% chance each day, especially Saturday). - Dry weather through at least Wednesday in a zonal jet stream pattern across the Rockies. - Probabilities of measurable precipitation, including snow, increase by late Wednesday into Thursday (24hr QPF probs increasing to 40+ %) && .DISCUSSION... Issued at 222 PM CST Thu Nov 21 2024 Water vapor loop and RAP analysis showed a mid-upper level ridge continuing to build and expand across the Rockies and High Plains. Only a few high clouds have moved across western Kansas, but otherwise very quiet weather continued, including a light/variable wind across western Kansas as a surface high pressure ridge moves across Kansas. For tonight, southwestern Kansas will remain under the influence of the departing surface high, but winds will slowly become southerly late tonight into early Friday. Persistence is a pretty good forecast method right now, so we will see lows tonight similar to that of last night, generally in the mid to upper 20s. The overall synoptic pattern will not change much on Friday, but as the air mass gradually modifies after a recent cold front passage, we should see afternoon temperatures exceed today`s highs by 6 to 8F across western Kansas, resulting in highs right around 60F for most of our forecast area. Heading into the weekend, a strong upper tropospheric Pacific jet core will push into the western CONUS and across the Rockies, which will foster a deepening of the leeside trough in the lower troposphere across the length of the High Plains. A lead shortwave trough moving out across the Northern Rockies and Dakotas will result in a cold front late Sunday across the Central Plains. Ahead of the front, more afternoon temps of the lower 60s are likely across much of southwest Kansas. As the leeside trough strengthens, so will the southerly winds, although the MSLP gradient will not be all that intense, so winds Saturday afternoon will likely be 10-15 mph. An extended polar jet core will overspread much of the CONUS with high zonal index, so the zonal pattern will lead to continued dry weather. Now, as we head deeper into the holiday week, there continue to be indications of a pattern shift as the large scale pattern amplifies just a bit, marked by a fairly strong disturbance, shown by all three of the major global models. This system, though, will still be moving east across the Central CONUS within a fairly fast/zonal hemispheric regime. This will prevent substantial Gulf of Mexico moisture transport into Kansas, but fairly strong large scale baroclinic zone in vicinity of the jet core would go a long way in aiding in upward vertical motion for at least some light precipitation wherever the Wednesday-Thursday wave comes out. Nevertheless, there is fairly high confidence in a low level air mass being cold enough for snow, so even light amounts of precipitation with Wednesday-Thursday system would have to be monitored closely for potential winter impacts. && .AVIATION /00Z TAFS THROUGH 00Z FRIDAY/... Issued at 516 PM CST Thu Nov 21 2024 VFR flight category with winds in general under 12 kts for all the terminals during the time period. && .DDC WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Umscheid AVIATION...Tatro
Area Forecast Discussion
National Weather Service Gray ME
1047 PM EST Thu Nov 21 2024 .SYNOPSIS... Low pressure will track north tonight, bringing rain to the area overnight. The broad system will be slow to exit, with chances for precipitation continuing through Saturday. Conditions will start to dry out Sunday into Monday as the low pressure lifts into the Canadian Maritimes. && .NEAR TERM /THROUGH FRIDAY/... 1035 PM Update... Latest RAP13 sfc pressure analysis as of 04Z shows the center of low pressure located over Long Island, NY with the h5 low further to the southwest over PA. Radar trends this evening have shown the vast majority of the rainfall streaming from southeast to northwest over NH and points south and west with a sfc trough leading mostly to just light drizzle over ME. Latest forecast guidance brings the low into the Hudson River Valley by Friday morning with our area on the northern periphery. Despite this, hi-res guidance including the HRRR continues to advertise a brief period of light to moderate rain to lift northward early Friday morning in association with the LLJ, dropping up to around 1/2" of additional rainfall on average. Therefore, while I lowered the QPF forecast for much of ME there are still indications that most locations should end with at least 1/3-1/2 inch of rain by late Friday morning. East-northeasterly winds have been on the increase this evening as well with coastal sites now gusting up to around 30 mph and offshore sites nearing 50 mph. The HRRR has been handling these winds pretty well this evening and the 00Z run indicates the potential for a brief period of gusts nearing 45 mph along the coast early Friday morning. In addition, strong downsloping winds northwest of the Whites could approach 50 mph for a brief time. Previously... 600 PM Update... Made some minor adjustments to PoPs based on latest radar trends and sfc observations. This generally delayed them some over much of western ME where weak forcing for ascent is still present but did introduce drizzle to the forecast based on observations. Otherwise, the inherited forecast remains largely unchanged at this time. Previously... Surface circulation continues to organize south of Long Island this afternoon as cyclogenesis takes place. This area of low pressure will give the final nudge north for rain that has mainly been focused in SW NH today. Showers begin, then become more steady overnight as this low wraps inland over central New England. Accompanying this low will be a brief but potent low level jet developing off the NH/southern ME coast overnight. Daytime deterministic solutions have this as a 40-60kt jet through 925/850mb, thus have increase surface gusts for much of tonight. HREF min gusts do push 30-40 mph along the immediate coast and southern NH tonight. Another zone of enhanced winds may be the downslope locations NW of the Whites and western ME mountains where gusts to 40 mph can`t be ruled out for a 4 or 5 hour window after midnight. As these winds move north through the area overnight, so too will more steady rainfall. Rain rates will be heaviest after midnight for the southern CWA, and after daybreak for western ME and the Midcoast. No flooding is expected with very dry antecedent conditions. && .SHORT TERM /FRIDAY NIGHT/... A dry slot moves northward through NH and southern ME Friday morning and early afternoon. This should offer a quick shutoff of both precipitation and the aforementioned gusts from overnight, but only up to the Kennebec Valley/western ME mountains. There was still a lot of discrepancy between guidance solutions heading into Friday night. This revolves around how resilient the dry slot will be as well as general progression of the low consolidation to the west. Additional onshore flow from the SE will advect moisture in later Fri afternoon to begin another period of stratiform precipitation across the area overnight. Rain is expected for the lowlands, but snow will feature more widely at greater elevations in the Whites, western ME mountains, and western NH Greenway, especially overnight. In general, accumulating snow may be hard to come by outside of the elevated Whites, but flakes will be about. && .LONG TERM /SATURDAY THROUGH THURSDAY/... 04Z Long Term Forecast Update... Latest ensemble and global forecast guidance continues to indicate unsettled conditions to persist on Saturday as low pressure drifts to the Canadian Maritimes. While doing so, colder air will be brought down from the north with northwesterly flow and this could allow for a brief period of wet snow to mix in south of the mountains before ending. Another s/wv trough looks to cross on Sunday, bringing additional rain/snow showers that will be mainly confined to the north/mountains. Brief s/wv ridging builds on Monday, allowing for dry and mainly sunny conditions. The pattern becomes more unsettled again mid-late week as the next storm system approaches the region. Broad upper low will be centered near Cape Cod Saturday morning, and waves of energy rotating to the north and west over the area will prolong cloudy and rainy conditions for at least the morning hours with snow toward the north and higher elevations (although a few flakes may mix in early farther to the south). The upper low will gradually move off to the northeast through the day and into Saturday night, and there`s still come uncertainty among the models on how quickly this occurs, but the general trend will be decreasing precip chances south of the mountains going into the afternoon and evening, although could be more Saturday night per the ECMWF. A surface low will also be deepening as it lifts northward into Nova Scotia, and with the tightening gradient expected breezy conditions to develop by the afternoon with gusts of 20 to 30 mph possible. Once precip tapers off, skies are expected to remain partly- mostly cloudy south of the mountains through Saturday night while the mountains stay cloudy with scattered upslope snow showers. Stacked low pressure will remain near the Canadian Maritimes on Sunday leaving northern New England in a northwest flow, which will be on the breezy side with a tight pressure gradient. Based on latest forecast soundings, we`re looking like upwards of 25-30mph. Rain and snow showers will likely continue across the north and mountains, and a few of these may occur downwind of the mountains if we can get enough daytime instability and Froude numbers are high enough (the NAM is more supportive of this) as there will be an upper trough nearby. The upslope precip in the mountains will wind down either Sunday night or early Monday as high pressure briefly builds into the region bringing a dry day with seasonable temperatures mainly in the 40s. As quickly as the high moves in, it will quickly give way to an upper trough and surface low moving across the Great Lakes that bringS the next shot at widespread precipitation Monday night and into Tuesday. Temperature profiles may be cold enough to support some snow or even a mix Monday night or Tuesday morning, but confidence is low and would probably be across northern areas if anywhere. After this system passes, there is a good support among the GFS and ECWMF ensembles members with dry conditions on Wednesday (other than mountain upslope snow showers). Going into next Thursday/Thanksgiving, the operational GFS is hinting at low pressure potentially bringing some snow to the area, but this is the faster solution with many of its ensemble members (as well as the ECWMF) keeping conditions mostly dry. The NBM PoPs of slight chance across southern areas capture this well. Lastly, there is pretty high confidence in a cooler airmass arriving toward the end of next week, and even though this is just beyond the extended forecast, there is a signal for what could be the first measurable snowfall of the season for many areas. This would potentially be in the day 8 or 9 time period, and as always this far out, details (such as amounts and timing) are uncertain. && .AVIATION /04Z FRIDAY THROUGH TUESDAY/... Short Term...MVFR and IFR cigs are expected overnight tonight along with increasing east winds and RA. Winds may gust 20 to 30 kts tonight as low pressure drifts into central New England. Winds slacken Friday morning as well as some improvement in restrictions with IFR becoming MVFR and perhaps VFR later in the afternoon. Another round of lowered ceilings arrives Friday night with RA. More in the way of SN may be possible along the western ME mountains and the Whites Friday night. Long Term...Rain along with IFR to MVFR ceilings expected at most TAF sites on Saturday, but conditions look to improve to VFR late in the day into Saturday night with the exception of HIE and LEB, where MVFR ceilings and possibly rain and snow showers continue through Sunday or even Sunday night. . Elsewhere, mostly VFR expected Sunday and Monday with northwest wind gusts 25-30 kt possible on Sunday. A few rain or snow showers may also develop Sunday afternoon. Another low pressure system looks to bring increasing precipitation chances Monday night and Tuesday along with flight restrictions. && .MARINE... Short Term...A period of Gales as well as increased wave heights is expected tonight. Low pressure strengthening south of Long Island will track north, with a strong jet moving along the coastal waters tonight. A window of 35 to 40 kt gusts will be possible overnight, before subsiding Friday morning. However, this will be part of a broadening area of low pressure across the Northeast. Another round of increased winds and building waves is likely into Friday night. Long Term...SCA conditions expected on Saturday as low pressure lifts northward toward Nova Scotia but remaining mostly east of the waters. With more of an eastward forecast, the potential for Gales during the day Saturday has lowered but will still be possible Saturday night and Sunday as offshore flow increases with a tightening gradient. Conditions may be able to fall below SCA levels late Monday or Monday night as high pressure briefly builds in before winds increase ahead of and also behind a low pressure and front that look to cross around Tuesday. Another area of low pressure may approach the waters toward the end of next week, but confidence is low on timing and potential track of the low. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Gale Warning until 6 AM EST Friday for ANZ150-152>154. Small Craft Advisory until 6 AM EST Friday for ANZ151. && $$ NEAR TERM...Tubbs SHORT TERM...Cornwell LONG TERM...Tubbs/Combs
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
530 PM CST Thu Nov 21 2024 .KEY MESSAGES... - Patchy freezing fog possible tonight and Friday night. - One last chance to get some outdoor work done on Sunday with highs in the 40s. - Turning much colder next week, with our first taste of arctic air looking increasingly likely for Thanksgiving weekend. - No significant winter systems expected to impact the region over the next week. && .DISCUSSION... Issued at 401 PM CST Thu Nov 21 2024 A surface low as been tracking south across Lake Michigan through the day, with high pressure over the Dakotas keeping the ceaseless northwest winds going through this afternoon. The good news is that through Saturday morning, the Dakotas high will be slowly working across the MPX area. This means we finally lose the winds on Friday, but the big uncertainty is what happens with the cloud cover. Looking at RAP soundings, we look to have a scenario where we have a thin moisture layer that gets trapped beneath an inversion. This time of year, that translates into very stubborn stratus layers that are poorly resolved by the models. As the high pressure moves in on Friday, the loss of cyclonic flow should start to clear out the low clouds, but those low clouds look to be replaced by mid and upper level clouds. The biggest issue with cloud cover will come during the overnight periods the next two nights. Winds will become light and variable overnight in western MN and then across the entire area Friday night as the surface ridge axis moves through. With this setup, anywhere that sees clear skies tonight in western MN will likely have that clearing filled in with freezing fog, with that freezing fog threat spreading across pretty much the entire area Friday night. Again, the big uncertainty is what cloud coverage will look like the next two nights. Given the uncertainty with cloud cover, we don`t have much fog mention, but anyone that manages to get light winds and clear skies over the next two night will have the threat of freezing fog. For the weekend, models continue to show a shortwave working across the international border Sunday night/Monday. This shortwave will drag an inverted surface trough across the area Sunday into Monday morning. The best forcing and signal for precipitation continues to be across the international border and Lake Superior, though we could see some light rain/snow across central MN and northwest WI late Sunday into Monday. The main impact locally of this inverted trough will be the WAA out ahead of it. This WAA will send highs into the 40s for much of the MPX area on Sunday, giving us one last chance to get some outdoor work done before some real winter cold comes slamming in for the end of November. As for next week, the mean 200mb flow from the EPS shows the primary jet being a southern stream feature that will be well to our south. This means the primary storm track will be to our south. However, there will be a northern stream jet of the northwest variety coming down from northwest Canada into the Dakotas. This northwest jet is what will open us up to getting our first real shot of arctic air of the season over the extended Thanksgiving holiday weekend. This is a cold a dry pattern, so it looks unlikely we`ll see any significant weather systems up this far north, but given the multiple streams of flow near us, we will have to potential for seeing some quick hitting waves capable of producing some light precip. Given the temperatures we will have next week, any precipitation we see will come in the form of snow. At this point though, deterministic and ensemble systems would favor any snow we see next week being more of the cosmetic/nuisance variety as opposed to a big dump of snow. && .AVIATION /00Z TAFS THROUGH 00Z FRIDAY/... Issued at 521 PM CST Thu Nov 21 2024 High end MVFR is expected to drop into low MVFR/IFR territory over the next few hours. Once again, models have not been handling cigs well today. Generally kept things a little more optimistic than guidance, which had more IFR than MVFR. Ceilings will rise by early Friday afternoon, with VFR expected for all except KEAU by the end of the period. Winds will remain elevated for a few more hours before trending down. A surface high is expected to move overhead tomorrow, leading to winds 5kts or less. KMSP...No additional concerns /OUTLOOK FOR KMSP/ SAT...Chc MVFR cigs. Wind NW 5-10 kts. SUN...VFR. Wind SE 5-10 kts. MON...VFR/MVFR w/ chc -SHSN. Wind NW 10-15G20kts. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None. && $$ DISCUSSION...MPG AVIATION...Dye
Area Forecast Discussion
National Weather Service Marquette MI
935 PM EST Thu Nov 21 2024 .KEY MESSAGES... - Scattered rain showers continue over the north tonight through Friday. - Light lake effect rain/snow showers are possible in the east half of the U.P. Saturday. Little to no accumulations are expected. - Active weather with chances for accumulating snow return next week. && .UPDATE... Issued at 935 PM EST Thu Nov 21 2024 The band of rain showers that camped out over the central UP for much of today is tapering off to lingering upslope rain showers across the north-central UP with the surface low south of Lake Michigan opening up to a surface trough and the midlevel low moving towards the Mid Atlantic. Winds continue to fall back, but should still be able to gust to around 20mph across much of the UP tonight...particularly across our eastern zones where our pressure gradient remains fairly tight. Winds to the west have been knocked back slightly to align with latest observations and model guidance, otherwise the forecast remains on track. && .SHORT TERM /THROUGH TONIGHT/... Issued at 322 PM EST Thu Nov 21 2024 Afternoon satellite imagery and RAP analysis show the sfc low has made it just south of central Lake MI. Aloft, the mid level low is analyzed over Lake Erie and OH with a ridge building in over the Plains. Satellite imagery also highlighted some well defined gravity waves earlier this afternoon in the low cloud deck near the MN Arrowhead shores of Lake Superior. This is where some weak sfc to 850 mb CAA, low level fgen, and pressure rises resulted in northwest katabatic winds. A few ship observations came in with storm force winds gusting into the low to mid 50 kt range! SAR wind data also shows that these winds extended into the northern open waters of LSZ162. Outside the marine impacts, pressure falls this morning and the tight pressure gradient resulted in northerly wind gusts up to 35 to 45 mph in the north half of the UP with 58 mph recorded at Houghton County Memorial Airport. This ended up causing some power outages this morning, but winds have already begun to weaken this afternoon. North winds have fallen below 15 mph over the eastern half of the UP with gusts still in the 15 to 25 mph range over the west. North winds of 10 to 20 mph are expected for tonight. Numerous showers have continued to dominate the central UP with scattered showers over the west and isolated shower to dry conditions over the east. Some clearing is even observed on satellite over the Lake MI shores of Upper MI and northern Lower MI. The sfc low is progged to descend over the rest of Lake MI into this evening, dissipating tonight as the mid level low spins toward the Atlantic Coast. This yields a eastward shift in the dominating band of showers before some dry air moves in from the north. Model soundings show the drier airmass intruding above the the 5-7 kft level, diminishing shower coverage and overall QPF. That said, scattered upslope and lake enhanced showers are expected tonight over the north. An additional few hundreths to 0.15 inches are expected over the western 2/3 of Upper MI this afternoon through tonight. Up to 0.6" of additional rain is forecasted over portions of Baraga and Marquette Counties aided by the upslope flow; most of the QPF is expected to fall during the next 6 hours. Overall, wet snow and rainfall over the past 24 hours has brought around 0.5 to 2 inches of liquid precip which should help improve drought conditions across the UP. Otherwise, temps currently in the upper 30s to mid 40s are expected to settle into the mid 30s to low 40s tonight. && .LONG TERM /FRIDAY THROUGH THURSDAY/... Issued at 334 PM EST Thu Nov 21 2024 Mostly quiet weather returns this weekend as ridging over the west- central CONUS nudges into the Upper Great Lakes this Friday, however, we wont completely dry out as northerly flow over Lake Superior and weak lake enhancement provide some light rain/drizzle through the day. Favored upslope locations in the central U.P. could pick up a few hundredths, otherwise not expecting anymore widespread showers. Some light snow is possible in the Michigamme Highlands as temperatures head toward freezing Friday night. Upstream, a shortwave diving southeast across northern Ontario Saturday kicks off a weak surface low over James Bay. Though the better synoptic forcing remains to our north, a shot of colder 850mb temps near -8 to -10C will provide enough lake induced instability for showers in the east half of the UP given northwest flow. Lake effect showers will likely start off as rain but transition to light snow as wet- bulbing processes take effect and colder air filters in the column. Little to no snow accumulation is expected, though some heavier showers could provide a light dusting for Alger and northern Luce counties in the evening. A brief period of height rises on Sunday will put an end to lake effect showers and our attention then turn to a deepening trough across the Plains digging into the Upper Midwest Monday into Tuesday. Current deterministic guidance and their respective ensemble packages are still in disagreement on the placement of the surface low and associated snowfall/gusty winds. Euro ensemble is much further north and faster with a surface feature in the vicinity of the UP/Lake Superior by Monday morning, while GEFS low locations are weaker and move the low through lower Michigan late Monday into Tuesday. Ensemble meteograms only show light snow accumulations up to a few inches by Tuesday evening. Looking towards Thanksgiving, ensembles are in agreement in a period of negative 500mb anomalies across the central US, supporting active weather with chances for accumulating lake effect snow in the Great Lakes region and possible hazardous travel conditions during the late week holiday timeframe. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 655 PM EST Thu Nov 21 2024 The coverage of rain showers will diminish across the area this evening; however, mainly IFR conditions are expected to persist across the area through the TAF period. For tonight, there is ~30% chance for showers streaming off Lake Superior, but best confidence in showers is at SAW. Northerly winds will diminish through this evening, becoming mainly 10-20 kt for tonight persisting into Friday. && .MARINE... Issued at 334 PM EST Thu Nov 21 2024 Surface low pressure near 998 mb is making its way down the long axis of Lake Michigan this afternoon, further weakening as it continues southeast into Indiana this evening. With the pressure gradient lessening over Lake Superior, widespread northerly gales are expected to diminish through the afternoon; however, localized terrain driven storm force gusts upwards of 55+ knots were observed by passing ships just offshore of the Minnesota Arrowhead just before Noon EST, prompting a short- fused upgrade to Storm Warnings in far western Lake Superior. These enhanced gusts should continue to dwindle below gale force criteria by at least midnight tonight. Winds turn out of the north-northwest Friday gusting to near 25 knots over the east-central lake, then continue diminishing below 20 knots by Saturday evening, calming further into Sunday. Gusty winds return late Monday into Tuesday as a low pressure system is forecast to impact Upper Michigan. As of this forecast package, confidence is low (~40%) on the low pressure center location and strength. A low closer to the UP could bring northwest gales to Lake Superior while a more distant low through Lower Michigan could keep winds marginal. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ UPDATE...LC SHORT TERM...Jablonski LONG TERM...BW AVIATION...RM MARINE...BW
Area Forecast Discussion
National Weather Service San Francisco CA
413 PM PST Thu Nov 21 2024 ...New AVIATION, MARINE... .SYNOPSIS... Issued at 222 PM PST Thu Nov 21 2024 Atmospheric River continues to remain stationary across the North Bay with increasing flood risks developing. Prolonged rainfall is additionally resulting in an increased risk of landslides, downed trees, and downed powerlines across the North Bay. More widespread moderate rain will spread south on Friday into the rest of the Bay Area and Central Coast. && .SHORT TERM... (This evening through Friday) Issued at 222 PM PST Thu Nov 21 2024 Key Messages: -Aerial Flood Warning now in effect for central Sonoma County -Numerous Flood Advisories cover the North Bay -Flood Watch in effect for the North Bay through Saturday morning -Wind Advisory in effect from 10 PM tonight through 10 PM tomorrow -High Surf Advisory in effect through Friday morning A stationary rain band producing moderate to at times heavy showers continues to train over the North Bay with the highest rain totals focused in Sonoma County. Most areas in Sonoma and Napa counties have seen between 5" to 10" of rain in the last 48 hours. Locally higher amounts between 10" to 15" have been observed across the higher elevations of the coastal and interior North Bay Mountains. Southwards in Marin County, rain totals are slightly lower with most sites seeing between 3" to 6" over the last two days. Rain totals drop off significantly outside of the North Bay with most sites in the northern San Francisco Peninsula and East Bay seeing less than an inch so far. Reports of flooding and downed trees have started to increase across the North Bay. As such an Aerial Flood Warning is now in effect for portions of central Sonoma County, including urban Santa Rosa, with creeks and streams starting to rise in the vicinity of the city. Heading into Friday, we can expect more widespread moderate showers to spread into the rest of the Bay Area and Central Coast late tonight through tomorrow. This will bring an additional 2" to 5" across the North Bay with locally higher totals possible in the elevated terrain. The majority of the Bay Area and coastal mountain ranges will see between 1.5" to 3" of rain while portions of the South Bay and Central Coast will see up to an inch. A slight (less than 10%) chance of thunderstorms will continue through Friday evening. The main things to focus on heading into Friday are 1) increased flood risk across the North Bay, 2) flood risk across the rest of the Bay Area and Central Coast as rain spreads southward, and 3) elevated wind threat tonight into tomorrow. Showers have not let up over the North Bay in over a day and a half. As such two things are happening 1) streams and creeks in Sonoma County are starting to rise with many already reaching the action to minor flood stages. Among the most notable, official forecast points have the Russian River at Geyserville peaking at minor flood stage, Russian River at Guerneville peaking at the action stage, and the Mark West Creek near Mirabel Heights peaking at the moderate flood stage tomorrow evening. Streams and creeks throughout the North Bay are expected to continue rising as moderate to at times heavy rain continues to train over the North Bay today and tomorrow. This brings us to our second point, 2) soil saturation. Prior to this event soils were fairly dry across the North Bay, but, after the last two days, soils are becoming fairly saturated. As the soil becomes more saturated, it is able to absorb less water and results in increased surface runoff, resulting in more widespread flooding. As such, a Flood Advisory remains in effect across the entire North Bay through early Saturday morning and a more targeted Aerial Flood Warning is now in effect for urban Santa Rosa. Elsewhere, flooding potential will increase slightly across the rest of the Bay Area and Central Coast as moderate showers spread southward Thursday night into Friday. Soils remain dry in these regions which help to slightly decrease flooding concern for this region. However, nuisance flooding is still a possibility especially if moderate to heavy showers train over a particular location for an extended period of time. Strong, gusty southerly winds return tonight with a Wind Advisory in effect from 10 PM tonight to 10 PM tomorrow night along the coast and across areas of elevated terrain. HRRR model guidance supports a narrow frontal rainband developing overnight Thursday into Friday and pushing southwards through the evening. Strong winds are expected to develop ahead of and along this rain band but will quickly ease after frontal passage occurs. Widespread wind gusts up to 50 mph are possible but locally higher 60+ mph gusts may develop above 2,500 feet. This will contribute to an increased risk of downed trees and power outages, particularly across the North Bay, as soils become saturated. Anyone who is able to should avoid being out during the worst of the storm (early Friday morning through Friday evening) should do so. If you have any outdoors decorations, now is the time to secure them. If you have to be out on Friday, make sure to leave extra time to get to your destination and avoid driving through flood waters. Waters overtopping roadways may be deeper and swifter than they appear and can result in a dangerous situation developing. Flooding can be particularly hard to see in the dark so use extra caution when traveling at night. Remember - turn around, don`t drown. && .LONG TERM... (Friday night through next Wednesday) Issued at 222 PM PST Thu Nov 21 2024 Friday night through Saturday, light showers will continue across the region in the wake of cold frontal passage. Totals from these showers will be relatively minimal (amounting to less than a few tenths of an inch) with a 10% chance of thunderstorms persisting through the day on Saturday. However, the storm door remains open as we see low pressure lingering off the coast of Washington/Oregon and increased moisture transport into Central California through midweek. While there is still some uncertainty as to how long rainy conditions will persist for, it is looking increasingly likely that rain will persist through midweek. As such, an additional 1" to 2" of rain is expected across the North Bay, Santa Cruz and San Mateo Mountains, and Santa Lucia Mountains from Sunday to Wednesday and up to an inch of rain elsewhere. Some potential light at the end of the tunnel, models have trended drier beginning Wednesday afternoon into Thursday but, given uncertainty in the forecast almost a week out, this may change as we get closer. && .AVIATION... (00Z TAFS) Issued at 413 PM PST Thu Nov 21 2024 Stratus continues to funnel through our region creating a mix of IFR, MVFR, and VFR conditions. North Bay continues to have lower visibility and ceilings as the showers remain pretty heavy. As the heavier rain bands move over some of the terminals in SF Bay, East Bay, and South Bay ceilings will lower to MVFR with a chance of IFR conditions starting early Friday morning going into the afternoon. Higher confidence that KHAF will be socked in with IFR conditions with some moments of MVFR through the TAF period. Southerly winds remain relatively breezy to strong with gusty winds near SF Bay terminals. The gusty winds have eased a bit over the North Bay, but will make a return late tonight for KSTS and early tomorrow morning for KAPC. Otherwise, most sites will continue to see gusty southerly winds through the TAF period. Vicinity of SFO...MVFR as a heavier rain band have moved over the terminal. Some models call for a break in MVFR ceilings near 08-09Z but had low confidence to include at this moment. Higher confidence that MVFR/IFR conditions will prevail after 14/15Z along with occasional heavier rain bands from 15Z to the end of the TAF period. Southerly winds have eased a bit with gusty winds diminishing. There is a chance for moments gusty winds between now until 14Z but low confidence to keep gusty winds prevailing through 14-15Z. Higher confidence that winds start to rebuild after 15-16Z to breezy and strong. Will monitor winds closely for any updated changes. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...VFR through most of the TAF period. There is a chance for MVFR ceilings to develop tonight but confidence is moderate. VCSH were added to the TAF closer to the end of the TAF period, but confidence is low, as showers may start after 00Z. Southerly winds will build to relatively breezy, but moderate confidence of gusty winds forming by the afternoon hours. && .MARINE... (Tonight through next Wednesday) Issued at 413 PM PST Thu Nov 21 2024 Widespread gale force winds will continue the hazardous marine conditions. Winds will range between 25 knots to 40 knots. Seas up to and just above 15 feet are anticipated with long period swell continuing to roll in. Widespread rain showers will result in gusty and erratic outflows and subsequent rough waters. Boating conditions will improve this weekend, but still remain quite hazardous, particularly to smaller vessels and crafts. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...High Surf Advisory until 6 AM PST Friday for CAZ006-505-509-530. Wind Advisory from 10 PM this evening to 10 PM PST Friday for CAZ006-502>505-509-512-514-515-517-518-530. Flood Watch through late Friday night for CAZ502>506. Beach Hazards Statement through late tonight for CAZ529. PZ...Small Craft Advisory until 3 AM PST Saturday for Mry Bay-SF Bay N of Bay Bridge. Gale Warning until 9 AM PST Friday for Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM. Gale Warning until 9 PM PST Friday for Pigeon Pt to Pt Pinos 10- 60 NM-Pt Reyes to Pigeon Pt 0-10 nm. Small Craft Advisory until 3 AM PST Friday for Pigeon Pt to Pt Pinos 0-10 nm. Gale Warning from 3 AM Friday to 3 AM PST Saturday for Pigeon Pt to Pt Pinos 0-10 nm. Small Craft Advisory until 9 AM PST Friday for Pt Pinos to Pt Piedras Blancas 0-10 nm. Gale Warning from 9 AM to 9 PM PST Friday for Pt Pinos to Pt Piedras Blancas 0-10 nm. && $$ SHORT TERM...Kennedy LONG TERM....Kennedy AVIATION...SO MARINE...Murdock Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea