Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/07/24


AREA FORECAST DISCUSSION
National Weather Service Albany NY
913 PM EST Sat Jan 6 2024 .SYNOPSIS... Our first major winter storm of the season impacts eastern NY and western New England tonight with moderate to heavy snow. Steady snow continues tomorrow morning before transitioning to snow showers in the afternoon and ending Sunday night. Dry conditions return Monday before our attention turns to our next widespread precipitation event for the middle of the week. && .NEAR TERM /THROUGH SUNDAY/... Radar and satellite trends show light to moderate snow over central and eastern NY spreading into western New England. The best isentropic lift, low level forcing and upper divergence is tracking across the eastern Catskills, mid Hudson Valley and NW CT and points south. The heaviest precipitation and deepest moisture are south of our region and moving east and northeast, possibly disrupting the better flow of moisture and low level forcing from building into our region. There are pockets of moderate snow in central and eastern NY but no organized bands or large areas. Snowfall rates have been in the 1/4 to 1/2 inch range with bursts around 3/4 of an inch per hour north of the eastern Catskills, mid Hudson Valley and NW CT. The NY Mesonet and reports from surrounding areas suggest 1 to 4 inches of snow in the past 6 hours and with the deepest moisture and cooling cloud tops in IR satellite image steadily moving east, there may be a lull in the steadier snow before daybreak, before the nest trailing upper energy and low level forcing tracks into our region toward daybreak, and affects our region with more periods of snow through the day Sunday. So, took snow amounts down a little bit for tonight from about I-90 northward, but still, some enhanced snowfall is possible in higher terrain due to upslope, especially in the southern Adirondacks, eastern Catskills and southern Green Mountains. However, even in those areas, a little less snow than previous forecast. Grand storm totals through Sunday are still 5 to 10 inches with some spots near a foot in higher terrain in most areas along and north of I-90, which still supports Winter Storm Warnings in most areas. Still expecting a storm totals through Sunday of a foot or more over areas south of I-90. PREVIOUS DISCUSSION: GOES16 water vapor imagery shows our southern stream shortwave intensifying over the Appalachians with strong upper level diffluence in the left exit region of our 300hPa jet resulting in our strengthening sfc low over the Delmarva Peninsula. Satellite imagery shows rapidly cooling cloud tops in response to the strong forcing for ascent with the storm`s precipitation shield expanding and advancing northward across the mid-Atlantic states. While the main precipitation shield is still to our south over PA, MD and NJ, some snow showers have developed ahead of it in Central NY and the Catskills with some ASOS and NYS mesonet sites showing light snow. Any snow showers will be light and with some dry air in the mid-levels (as seen on the 12 UTC ALY sounding), any snow that does reach the ground will only result in coatings. The main precipitation shield that will be responsible for our moderate to heavy snowfall is still progged to reach our northern/eastern Catskill and mid-Hudson Valley locations by 21 to 00 UTC before spreading north and eastward early this evening. The RAP and HREF have handle the onset timing the best of all the high res so we adjusted POPs based on this guidance. && .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... * Winter Storm Warnings remain in effect for all of eastern New York and western New England tonight through tomorrow evening.. * Avoid any unnecessary travel tonight as heavy snowfall rates will lead to dangerous travel conditions and reduced visibilities. Snow arrives from southwest to northeast this evening with snow reaching the Mohawk Valley and Greater Capital District by 00 - 03 UTC before advancing into the southern Adirondacks, Upper Hudson Valley, and western New England by 03 - 06 UTC. Strong isentropic lift combined with mid-level frontogenesis on the leading edge of our winter storm will produce moderate to heavy snowfall rates quickly after snow begins. Forecast soundings support lift intersecting the dendritic snow growth zone which will support snowfall rates ranging 1 to 1.5 inches through about 06 - 08 UTC for much of the area. This is supported via the latest probabilistic guidance from the HREF and DESI. Travel conditions will be especially dangerous during this time as heavy snow results in reduced visibilities and snow efficiently accumulates. With high pressure positioned in northern New England, the isallobaric wind component may help drain chilly air currently in the North Country southward. Thus, we sided with the NBM10th for temperatures showing many dropping into the 20s tonight. In addition, northeasterly winds in western New England turn breezy tonight with gusts up to 25-30 kts possible. Easterly 925hPa winds increase to around 30 kts during this time and local ALY research has shown that these wind regimes enhance snowfall amounts in the eastern slopes of the eastern and northern Catskills, southern Adirondacks, Rensselaer Plateau, northern Berkshires, and southern Greens. Therefore, snowfall rates up 2 inches per hour are likely in these higher terrain areas. On the flip side, this wind regime will likely lead to precipitation shadowing in Washington County and western Bennington County and even parts of northern Herkimer and Hamilton County due to blocked flow from the southern Greens and southern Adirondacks. Thus, lower snowfall rates are expected here. Our coastal low tracks off the coast of Long Island and escapes towards Cape Cod after 06 UTC. As a result, the strongest forcing for ascent will shift eastward out of our area resulting in lighter snowfall rates. In fact, high res guidance suggests that the associated mid-level dry slot will intrude into parts of our forecast area, especially the mid-Hudson Valley, Berkshire and Litchfield County. While this will reduce moisture in the DGZ and thus will reduce snowfall rates, moisture should be maintained in the lower levels so light snow should still continue for the rest of the overnight. We did, however, reduce POPs, south of I-90 to account for the dry slot and added brief sleet mention for the I-84 corridor. Total snowfall by Sunday morning likely ranges 6 - 10 inches across much of the forecast area with 12 - 15 inches likely in the aforementioned favorable upslope higher terrains. Light snow early Sunday will likely turn moderate once again by mid to late morning as the upper level trough moves overhead and we enter into the upper level deformation of the intensifying coastal low. Snowfall rates will not be as high as seen overnight but rates 0.5 - 1 inch per hour may return through early Sunday afternoon. Expect an additional 1 to 3 inches with potential for 2 - 4 inches if local mesoscale banding can develop. Snowfall rates decrease mid to late Sunday afternoon as the coastal low exits even further out to sea but with the parent shortwave intensifying into a cut-off low, mid-level moisture lingers over much of eastern NY and western New England through the rest of the daytime and even into Sunday evening. However, without the strong forcing in play, additional snow accumulations will be light with only up to around one inch or so expected. The majority of the snow should finally end Sunday evening (00 - 03 UTC Monday) but with winds shifted to the northwest, snow showers will likely linger in the favorable upslope areas of the southern Greens, northern/eastern Catskills, and southern Adirondacks. Overnight temperatures Sunday night turn chilly as clouds partially clear, dropping into the upper teens to low 20s. Total snowfall for this winter storm ranges from 8 - 12 inches with 12 - 18 inches in the higher terrain areas of the northern/eastern Catskills, southern Adirondacks, Berkshire County, and southern Greens. Lower amounts of 4 to 8 inches expected in Washington County, NY into western Bennington County, Vt as well as parts of northern Herkimer/Hamilton Counties due to blocking effects from the southern Greens and southern Adirondacks. High pressure builds in for Monday resulting in mostly sunny skies, seasonable temperatures, and breezy conditions thanks to the sfc pressure gradient overhead. Effective radiational cooling conditions expected Monday night given clear skies, light winds and a fresh snow pack. We sided with the cooler end of guidance for low temperatures with many expected to drop into the teens. && .LONG TERM /TUESDAY THROUGH SATURDAY/... The active and progressive pattern continues through the long term period, bringing additional chances for rain and snow, as well as potential high wind and flooding hazards to the region through the end of the workweek and into the upcoming holiday weekend. A deep upper trough over the Central Plains will support the development of a surface cyclone over the Mississippi Valley which will subsequently deepen as it tracks northeastward toward the Great Lakes. The upper trough will become negatively tilted as it approaches the Northeast, with potent northward advection of relatively warm and humid air on its eastern flank within a 60-80 kt south-southeasterly low-level jet, a +4-5 SD anomaly per the latest NAEFS guidance. This anomalous flow may additionally bring PW nearing 1" to southern zones and in excess of 0.75" to much of the region, as IVT reaches some 4-6 SD above normal for this time of year. Diffluence ahead of the upper shortwave will further increase the synoptic support for lift and chances for heavy precipitation across the region. As the surface low approaches from the southwest and the LLJ impinges on the region, strong, gusty winds may develop due to downslope enhancement on the western slopes of the southern Greens, Berkshires, Taconics, and Adirondacks where gusts may reach 30-50 mph on Tuesday. Cold, dry high pressure in place over the Northeast ahead of the aforementioned system may allow for precipitation to initially fall as a burst of snow for much of the region, or as rain/snow mix in the warmer fiver valleys, by Tuesday afternoon before transitioning to rain across the area as warm advection increases. Temperatures won`t be able to fall very far from Tuesday highs in the upper 20s to low 30s in higher terrain and mid 30s to mid 40s at lower elevations to Tuesday night lows in the upper 20s to upper 30s across the region as rainfall spreads northward overnight. Within warm advection on Wednesday, temperatures rise well above normal as highs reach the upper 30s to low 40s in high terrain and mid 40s to low 50s at lower elevations. Periods of heavy rain are possible Tuesday night into Wednesday morning as the surface low makes its closest approach as it passes to the west of the region. Upslope terrain enhancement on southeast facing slopes will provide additional forcing for heavy rain, with particular concern in the eastern Catskills. Given the widespread snowpack which will be in place across the forecast area, potential flooding due to heavy rain could be exacerbated by snowmelt contributions to additional runoff. As such, WPC has maintained a Slight Risk for flooding from excessive rainfall over the eastern Catskills, Mid-Hudson Valley, Taconics, Berkshires, and Litchfield Hills for Tuesday and Tuesday night, with a Marginal Risk farther north including the Mohawk and Schoharie Valleys, the Greater Capital District, and southern Vermont. Multi-model ensemble river forecasts additionally suggest at least 30% chances of minor or moderate flooding on many area rivers and streams, particularly south and east of Albany. See the hydro discussion below for additional details. As rainfall ends Wednesday evening into Wednesday night, westerly low-level flow and cold advection arrive behind the cold frontal passage. Lake-effect snow showers developing late Wednesday may persist through Thursday and much of Friday across the southwestern Adirondacks and western Mohawk Valley. Otherwise, brief upper ridging overhead will yield a return to dry conditions for the rest of the region for Thursday and Thursday night. Temperatures trend down toward seasonable values, with highs in the upper 20s to mid 30s in high terrain and upper 30s to mid 40s at lower elevations on Thursday and Friday, while lows dip into the upper 10s to upper 20s across the region Thursday and Friday nights. Yet another deep upper trough and associated surface low looks to approach the region late Friday, bringing additional chances for rain and snow into the holiday weekend. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... Snow is spreading over the region and conditions at all TAF sites will become IFR, with periods of LIFR through the night. The snow is expected to continue through most of Sunday, but the intensity may lighten up a bit, allowing for some periods of MVFR conditions. Winds will be light from the northeast and east at less than 10 Kt tonight, although, some gusts around 15 Kt are possible at KPSF. Northeast to east winds continue Sunday at 10 Kt or less but will be gusty at KPSF, up to 20-25 Kt. LLWS is possible tonight at KALB, KPOU and KPSF with winds at 2000 feet east to southeast at 35-45 Kt. Outlook... Sunday Night: No Operational Impact. NO SIG WX. Monday: No Operational Impact. NO SIG WX. Monday Night: No Operational Impact. NO SIG WX. Tuesday: High Operational Impact. Breezy. Likely RA...SN. Tuesday Night: High Operational Impact. Windy With Gusts To 32 kts. Definite RA...SN. Wednesday: High Operational Impact. Windy With Gusts To 31 kts. Definite SHRA...RA. Wednesday Night: Low Operational Impact. Slight Chance of SHRA. Thursday: No Operational Impact. NO SIG WX. && .HYDROLOGY... Widespread moderate to locally heavy rain is expected Tuesday night through Wednesday as a anomalously moisture rich disturbance impacts the Northeast. Antecedent conditions are wet given recent heavy rainfall events in Decembers and with a snowpack on the ground, the combination of heavy rain and some snow melt may result in both river and localized flooding. Guidance has been consistently showing this event for multiple days so confidence is growing for yet another hydro event. In fact, the Weather Prediction Center continues to place much of eastern NY and western New England in its marginal and slight risk in its Day 4 Excessive Rainfall Outlook. In addition, the Northeast River Forecast Center has outlined our eastern Catskill, mid- Hudson Valley and NW CT areas in its Significant Flood Outlook for this period as well. While heavy rain looks likely, there are some uncertainties regarding how much snow melt can take place as the snow pack needs to ripen before it can melt. Even still, temperatures are expected to warm well above normal Tuesday night through Wednesday including dew points rising into the 40s so some snow melt is expected. Those prone to river flooding should maintain a close eye on the forecast over the coming days. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...Winter Storm Warning until 7 PM EST Sunday for CTZ001-013. NY...Winter Storm Warning until 7 PM EST Sunday for NYZ032-033- 038>043-047>054-058>061-063>066-082>084. MA...Winter Storm Warning until 7 PM EST Sunday for MAZ001-025. VT...Winter Storm Warning until 7 PM EST Sunday for VTZ013>015. && $$ SYNOPSIS...Speciale NEAR TERM...NAS/Speciale SHORT TERM...Speciale LONG TERM...Picard AVIATION...NAS HYDROLOGY...Picard/Speciale
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1020 PM EST Sat Jan 6 2024 .UPDATE... In light of inbound radar returns, the degree of elevated ascent set to overspread Se Mi late tonight into Sun morning is a little stronger than earlier expected. There is also some concern in that RAP soundings show respectable supersaturation with respect to ice within the dendritic growth layer. There have nudged pops and snowfall totals up a bit from the earlier forecast. Can not rule out the potential for some half inch to inch type accumulations as temperatures hold largely around or just below freezing. Left some room for the potential for further adjustments based on observational trends and the arrival of the full 00Z model suite. && .PREV DISCUSSION... Issued at 555 PM EST Sat Jan 6 2024 AVIATION... An area of light snow will exit northeast of the terminals shortly after TAF issuance with the passage of a short wave impulse. After some rebound in ceilings heights per area observations, upstream observations and model guidance suggest lower clouds will advance across Se Mi during the course of the night. Probabilities for IFR ceilings actually become quite high late tonight and through Sunday morning. Broad troughing along and at the surface will sustain some weak forced ascent tonight and Sunday. With increasing moisture and thermal profiles supportive of snow, light snow showers/flurries are again expected late tonight into Sunday. For DTW...The next rough of light snow and reduced ceilings/visibilities across Illinois should expand across metro Detroit after 08Z. DTW THRESHOLD PROBABILITIES... * Moderate to high in ceilings aob 5000 feet this afternoon through tonight. * Moderate in precip type being snow today and tonight. PREV DISCUSSION... Issued at 308 PM EST Sat Jan 6 2024 KEY MESSAGES... - Nuisance snow showers this weekend to bring minimal accumulations as temperature reach the mid 30s both days. - Surge of moisture in advance of developing winter storm to the west will bring a burst of heavy, wet snow Tuesday morning with a few inches of accumulation expected before snow changes to rain by afternoon. - This strong winter storm will then track through the region into Wednesday with lingering rain and a possible change back to snow with additional light accumulations possible for some areas. - A wintry pattern will continue through the week with several more storm systems bringing possible accumulating snow followed by much colder conditions next weekend. DISCUSSION... Scattered light snow showers will persist this evening as upper low pressure lifts into northern Lower MI and vorticity lobes pivots through the area around the base of this low. Any accumulations, well under an inch, should be confined to grassy surfaces given the relatively mild conditions in place. Flurries may persist overnight before a second period of slightly enhanced snow shower activity works into the region Sunday morning as a secondary channel of vorticity shears through the area and provides a period of lift as minor surface low pressure reflection develops from southern Lake Michigan and then fills as it cross the area. This Sunday morning activity will be focused along and south of M-59 and again any minor accumulations under an inch should mainly occur on grassy surfaces as temperatures once again climb into the mid 30s. After a dry period from late Sunday on into Monday evening as high pressure translates east across the area, attention will turn to a strong winter storm developing to the west. The initial impact from this system will come early Tuesday morning as the warm conveyor in advance of this storm system is driven north within the corridor of a substantial low level jet (H85 40-60 kts). Expected an area of strong lift associated with this surge of warm air advection, aided by left exit region of strong H3 upper jet nosing into the area and coupling to some degree with massive anti-cyclonically curve jet more in the H2 layer as it brushes the area on its way into the northeast CONUS. This will lead to a rapidly expanding area of snow which should lift into the forecast area from the pre-dawn hours of Tuesday on through the rest of the morning. Given the degree of lift involved, suspect a fairly heavy burst of heavy, wet snow will be possible over parts of the area early Tuesday morning with this area then shifting east in the mid/late morning period. Continued broad scale lift with then maintain precipitation throughout the day Tuesday into Tuesday night with a changeover to rain with time on Tuesday afternoon as the surge of mild/moist air continues north through the area in advance of the center of this storm system. The storm will then mature and track over or just west of the region by Wednesday. There will be a tendency for the rain to mix with or change back to snow Wednesday as colder air associated with the core of the storm system wraps back east into the area. Precipitation will also become more inconsistent as a mid level dry slot also wraps into the area as the low pressure center lifts into lower MI. This period of the forecast will be largely defined by the west to east orientation of the winter storm by the time it ejects into the Great Lakes. With the current consensus, the heaviest snow (outside that initial burst Tue AM) will hold well west of the region with only minor accumulations as leftover snow wraps back into the area Wednesday as the system passes. A wintry pattern sets up for the rest of the week into next weekend as the next Pacific shortwave races quickly into the area by around Thursday and brings the potential for light snow or perhaps a rain and snow mix into Friday. Yet another strong shortwave will then encroach on the area by early next weekend with some potential for widespread snow. Confidence in the track of this system remains very low at the moment. Temperatures through the week will remain in the 30s with a much colder air mass just beginning to spill into the region over the weekend after the passage of that potential storm system. MARINE... Weak low pressure tracks eastward this evening bringing chances for snow to the region, with the highest chances for precipitation over northern Lake Huron. Easterly flow will die down overnight before flipping to westerly flow tomorrow. Wind speeds briefly pick up Sunday evening peaking at 15-20 knots. After a brief period of high pressure following the current low pressure, the next big system slated to move in will impact the region beginning Tuesday into Wednesday. A deep upper level trough will bring the storm track up from the southwest, bringing chances for precipitation and high winds over the lake. Sustained southeast flow followed by a shift to northeast will give chances for gale force gusts Tuesday evening and Wednesday morning. Confidence on the gale event is low at the moment, but hazardous conditions still have the potential to materialize. HYDROLOGY... Developing low pressure to the west will lead to an expansion of precipitation into the area Tuesday morning. This precipitation will begin as snow early Tuesday morning and transition to rain during the afternoon with rain continuing into Tuesday night. Given the degree of moisture that will be pulled up from the Gulf of Mexico, current forecast rainfall amounts for the day Tuesday range from around an inch near the Michigan and Ohio state line to one third to one half an inch north into the Saginaw Valley and Thumb. While significant flooding is not expected, these rainfall totals will be sufficient to produce minor flooding in low lying and poorly drained areas as well as ponding of water on roadways once the initial snow melts. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ UPDATE.......SC AVIATION.....SC DISCUSSION...DG MARINE.......BC HYDROLOGY....DG You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Quad Cities IA IL
527 PM CST Sat Jan 6 2024 .KEY MESSAGES... - Winter storm Monday - Tuesday Night - Another wintry system possible late next week - Very cold air arriving for next weekend && .UPDATE... Issued at 521 PM CST Sat Jan 6 2024 Around 4 PM, I updated to increase pops to likely to categorical for the ongoing light snow. This light snow has accumulated on grass outside our office to 0.2", and that`s probably less than what it`s doing to to our east, thus graphics and grids have been updated for the 1/2 inch snow event this evening, with marginal surface temperatures for road impacts, which could be slick in spots, but probably mainly wet in most locations. The snow should taper off from west to east between 6 pm and 10pm. && .SHORT TERM /THROUGH SUNDAY NIGHT/... Issued at 250 PM CST Sat Jan 6 2024 Flurries and light snow are ongoing along and east of the MS River with otherwise low clouds and patchy aviation fog with visibilities mostly 2 to 5 miles. This is as a result of an upper level wave currently sweeping across the region. Added at least flurries into the forecast with some slight/low chances for mainly light snow through the evening and overnight. The best chances will be along and east of the MS River where a light dusting to a half inch of snow will be possible. Little to no impacts from this snow are anticipated. The current forecast has the snow ending by 6 AM, but the HRRR is hinting that some flurries or light snow may linger across the NE half of the CWA into Sunday. Some partial clearing is forecast for Sunday afternoon with clouds returning Sunday night ahead of the system for Monday. Lows tonight will slip into the mid 20s to low 30s. Highs Sunday will be in the lower and middle 30s. For Sunday night, temperatures will be a little colder with most of the CWA in the 20s. && .LONG TERM /MONDAY THROUGH SATURDAY/... Issued at 250 PM CST Sat Jan 6 2024 Monday through Wednesday...Winter Storm Discussion Our well advertised and discussed winter storm remains on track in latest model guidance to impact portions, to a good chunk of eastern Iowa, northwest Illinois and northeast Missouri. The strong trough of low pressure that is going to be responsible for our winter storm is currently over the Pacific Northwest, and is beginning to get good sampling with surface observations, RAOBs and the hurricane hunters. Latest deterministic guidance shows this trough traversing the western CONUS and Rockies over the weekend, becoming a closed low as diffluence aloft from a very strong jet streak strengthens. This closed low will make its way towards the Four Corners and eventually the Texas/Oklahoma panhandles by midday Monday, where strong cyclogenesis is poised to take place in the low- levels and the development of a surface low. Both the closed low aloft and the surface low are progged to deepen relatively quickly as they traverse the central Plains into the mid-Mississippi Valley with help of strong diffluence with the jet aloft, and very strong CVA accompanying the closed low aloft. This system will find itself in the Midwest beginning Monday night, with a wide variety of impacts expected through Wednesday. As has been talked about in great detail lately, deterministic model guidance, and to an extent more conservative ensemble guidance, has been rather jumpy on the system track, ultimately shifting around the axis of heaviest snowfall. Not shockingly (given we are still 3- 4 days out) 12 UTC guidance from today has been no different. However, several things do remain consistent. First, as mentioned in the previous AFD, the heaviest deformation snow band position generally remains consistent, which looks to stretch from western Missouri into north central Illinois (roughly a Warrensburg MO - Quincy IL - Chicago IL line). This is supported by the LREF and ECMWF ensembles (and to an extent its deterministic), which have shown this trend in most of their latest model runs. Second, its going to be really windy. With a very strong jet aloft promoting strong divergence as the system tracks over the Midwest, the surface low is expected to deepen quite rapidly and promote a tight pressure gradient from the Ohio River Valley to the Midwest. As was mentioned yesterday, probabilistic guidance continues to hint at a medium to high chance (50-80%) of wind gusts near 40 MPH through much of the storm`s duration, especially Tuesday afternoon and overnight into Wednesday. Probabilities for wind gusts around 45 MPH or greater are much lower (10-30%), but that should not discount the fact that winds could lead to additional impacts through the event. Given the spatial distribution still evident on most deterministic models, will continue to advertise more of a probabilistic forecast with this fcst package. ECM and GEFS ensembles are consistent in an impactful snow (> 3 inches) roughly along and south of a Freeport IL to Ottumwa IA line, with > 6 inch probabilities (70- 100%) focused mainly along the aforementioned heaviest deformation snow band position in the previous paragraph. This includes much of southeast Iowa, west central Illinois and northeast Missouri. The snow that falls Monday night into Tuesday morning is likely to have the most impacts given temps daytime Tuesday will be in the low 30s. Given the uncertainty of the rain/snow line, how daytime temps in the low 30s Tues could impact snowfall totals and lack of sampling of jet streak with this system over the Pacific, decision was made in collaboration with surrounding offices to hold on a Winter Storm Watch in this forecast package. Regardless, those in eastern Iowa, northwest Illinois and northeast Missouri that have plans early next week should continue to monitor the latest forecasts. Thursday... A shortwave riding on a poleward exit region of an upper level jet streak will arrive across the area just in time for the Thursday AM commute, which is likely to bring a light, fluffy snow areawide. Too early to get into specifics at this time. Friday and Saturday... Guidance remains consistent on another storm tracking across the Midwest, which has potential to bring impactful snow to the region. Will have to keep a closer eye on this as colder air will be in place ahead of this system, which could lead to more impacts. More details on this will be in later forecast packages. Following this system, a deep Arctic air mass is poised to build across the Plains, Great Lakes and Midwest as we head into next week. While there are a quite a few variables (eg. snow cover) that could impact how cold we get, probabilities are there in latest ensembles for lows next Saturday and Sunday to fall well into the single digits (60-90%). This falls in line with the CPC 6-10 and 8- 14 Day temp outlooks, which favor below normal temperatures for the region. && .AVIATION /00Z TAFS THROUGH 00Z MONDAY/... Issued at 521 PM CST Sat Jan 6 2024 Widespread stratus cigs between 1000 and 2000 ft will continue tonight, with the light snow ending, but light fog continuing through 12Z in Illinois, and through around 08-10Z in Iowa, when west winds will increase, and drier air will arrive. A slow improvement in cigs will continue through the day Sunday, with some VFR conditions expected to be widespread by 18Z. In the next few hours, the light snow over Illinois will move east of all terminals, with little accumulation on any ground surface, but a dusting to 1/2 inch on elevated surfaces. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...None. IL...None. MO...None. && $$ UPDATE...Ervin SHORT TERM...14 LONG TERM...Speck AVIATION...Ervin
Area Forecast Discussion
National Weather Service Grand Junction CO
502 PM MST Sat Jan 6 2024 .KEY MESSAGES... - Dry weather prevails through early evening before activity redevelops over the southern mountains. Snow becomes more widespread tonight through Monday. - The highest totals will be in the southern mountains and valleys. The highway 550, 160 and 491 corridors can expect 8-16 inches of snow, along with winds gusting up to 45 mph. The southern valleys will receive 5 to 12 inches with winds gusting to near 40 mph. Travel will be impacted due to slick, snow-packed roads as well as reduced visibility in blowing and drifting snow. - Light to moderate accumulations are expected in the northern and central valleys with upwards of 6 inches possible in east- central Utah due to banding. - An active weather pattern will keep temperatures cold this week. More snow returns Wednesday, Thursday, and next weekend. && .SHORT TERM /THROUGH SUNDAY NIGHT/... Issued at 414 PM MST Sat Jan 6 2024 Quiet weather has prevailed this afternoon (apart from some light snow over the Elkhead and Park Mountains) as a weak, transitory ridge remains in place. Clearing skies are evident on satellite across eastern Utah, but observations also show the next round of dense cloud cover is on our doorstep. The next trough of low pressure will continue to dig into the Pacific Northwest this afternoon, engulfing the entirety of the western CONUS in response. Flow aloft will shift to the southwest as a result, tightening into the overnight hours as the low sinks into the Great Basin. While there isn`t an abundance of moisture associated with this system, with PWATs only peaking at 100 to 120 percent of normal, intense broad scale ascent will be more than enough to get things going. Scattered showers will kick off across mainly the mountains in southeast Utah and southwest Colorado late this evening before spilling into the adjacent valleys by midnight. Strong upslope flow will enhance rates over these areas, particularly the Southwest San Juans and Highway 160 corridor from Cortez east towards Wolf Creek Pass. Rates will exceed 1 inch/hour and they could potentially reach 2 or more inches per hour, as confidence continues to increase regarding heavier bands of snow developing late tonight and into Sunday morning. Not only will the southern tier of the forecast area be receiving periods of moderate to heavy snow from this event, but the continued tight gradient aloft will fuel gusty winds at the surface, generally on the magnitude of 35 to 45 mph. This will lead to increased travel impacts as these stronger winds bring about blowing and drifting snow, reducing visibility to less than a mile, or even less over the mountain passes. Therefore, the ongoing Winter Storm Warnings remain in place, although did cut off a bit from the end time to account for the drier weather and lower snow rates on Monday morning for several zones. Please use caution as this storm impacts the West Slope by checking the latest forecast and road conditions before heading out. As far as impacts to other portions of the forecast area...the aforementioned banding potential has led to higher snowfall projections across the Canyonlands / Natural Bridges and Arches / Grand Flat areas in eastern Utah. The NAMNest is hitting the intensity of the bands a bit harder than the HRRR but, either way, a band straddling the central portion of Utah Zone 29 and another one over the Bookcliffs at the northern edge of Zone 27 overnight will enhance rates in these areas. Therefore, went ahead and added both of these areas to the Winter Weather Advisories starting tonight. If the bands do not materialize as expected, or even reside longer, snowfall totals will be subject to change. Either way, expect travel impacts along the I-70 corridor from the Utah / Colorado border tonight and early Sunday. While some higher amounts close to 4 inches will bleed over into the far western portion of the Grand Valley, the rest of the zone will be sub-advisory. This trend continues going along the rest of the I-70 corridor with generally 1 to 3 inches possible. Drifting farther north, the East Tavaputs and Roan Cliffs will generally see 5 to 7 inches of snow, so opted to leave them out of the highlights as well. The same can be said elsewhere in the forecast area with only light accumulations expected in the northern valleys and mountains. We`ll continue to monitor things though as this storm moves through. By late Sunday morning the trough axis will be just outside our border before its center tracks over the Four Corners later that evening. This will keep conditions unsettled across the southern zones and locations along the Divide, while drier air invading from the north will see showers slowly taper off Sunday night over northeast Utah and northwest Colorado. Even with plenty of clouds lingering on Sunday night, overnight lows will drop to near or several degrees below normal area-wide. && .LONG TERM /MONDAY THROUGH SATURDAY/... Issued at 414 PM MST Sat Jan 6 2024 Model ensembles are indicating a significant shift in the weather pattern with a cold dome of air sliding south over the CONUS through the coming week that pushes the jet stream and storm track south forming a mid to upper level longwave trough across the continent that will last into the foreseeable future. A train of shortwave troughs and weak ridges transiting the region every few days will keep the weather generally unsettled with light orographic mountain snow showers under the passing ridges becoming more moderate and widespread across the region with the passing troughs. Clearing skies in eastern Utah and the far western Colorado along the Utah Border with each passing ridge will promote radiative cooling setting up inversions in the valleys. Current guidance suggests Tuesday and Friday mornings are prime for these conditions. Temperatures will start the week near normal to five degrees below normal in the lower elevations and five to ten degrees below normal in the mountains. As the colder air moves south through the week, these temperatures will drop to about ten degrees below normal and 20 degrees below normal respectively. Should the overnight clearing happen, expect temperatures to drop another ten degrees Tuesday and Friday, especially in the favored cold spots. Winds in the valleys remain on the light side keeping the low level moisture in place making fog and low stratus possible under inversions through the period and feeding the orographic showers in the mountains favoring the northern and western faces. A shortwave passing to the northeast will bring increased snow showers to the northern mountains Tuesday night spreading south into the central Colorado mountains Wednesday. Mid level moisture from a weak AR slipping through the Oregon gap will get pulled into this system increasing the potential for heavier snow in the northern mountains. A second shortwave hot on the first`s heels will push the showers into the southern mountains Thursday. Currently the snow accumulation expected from these waves remains borderline advisory level with no winter weather headlines anticipated at this time. Stay tuned for updates as this may change over the next few days. A third shortwave next weekend looks to bring yet more snow to the region supported by moisture from a second weak AR squeezing through the Oregon gap Saturday, but it`s too far out to really look at snow fall totals from this system. Expect this unsettled weather to continue into the following week. We may not see a big storm dump on us, but slow and steady builds the snow pack just as well. && .AVIATION /00Z TAFS THROUGH 00Z MONDAY/... Issued at 500 PM MST Sat Jan 6 2024 VFR conditions with increasing mid and high clouds will occur this evening with snow increasing across the area after 06Z. Snow will be fairly widespread with most TAF sites seeing VCSH with mountain obscuration through the day on Sunday. Tonight through Sunday morning, snow will fall across southeast Utah and southwest Colorado before spreading into the central and northern zones Sunday afternoon and evening. Conditions will be below ILS breakpoints especially across the south due to low CIGS and VSBY. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...Winter Weather Advisory from 11 PM this evening to 11 PM MST Sunday for COZ003. Winter Storm Warning from 11 PM this evening to 5 AM MST Monday for COZ009-017-021>023. Winter Weather Advisory from 11 PM this evening to 5 AM MST Monday for COZ012-020. Winter Storm Warning from 11 PM this evening to 8 AM MST Monday for COZ019. UT...Winter Weather Advisory from 11 PM this evening to 11 PM MST Sunday for UTZ025-029. Winter Storm Warning from 11 PM this evening to 5 AM MST Monday for UTZ022-028. Winter Weather Advisory from 2 AM to 5 PM MST Sunday for UTZ027. && $$ SHORT TERM...MMS LONG TERM...DB AVIATION...MDA
Area Forecast Discussion
National Weather Service Marquette MI
641 PM EST Sat Jan 6 2024 .SHORT TERM...(This evening through tonight) Issued at 251 PM EST SAT JAN 6 2024 Light snow continues across most of the area with RAP analyses showing a weak midlevel trough swinging through the Great Lakes. With surface temperatures in the upper 20s to near 30F and a rather warm airmass aloft (850mb temperatures only around -8C), SLRs are on the lower end at around 10-12:1 so far. IR imagery shows the back edge of this first wave of snow moving into the UP, and surface observations indicate that snow is tapering off over western WI and far western Upper Michigan. However, with persistent southeast flow over the area, lake enhanced snow should linger into the evening hours in the eastern and central UP. Up to a tenth of an inch of QPF is expected in the SE lake effect areas of the east and central UP, and in the Keweenaw, with lighter amounts elsewhere. This should widespread totals of a trace to half an inch the rest of today and into the evening, with locally higher amounts around or just in excess of an inch where lake enhancement occurs. As snow largely tapers off later this evening, expect cloudy skies and patchy fog to linger into the night while temperatures drop into the mid 20s. An approaching cold front will touch off our next chances for light snow in the western UP heading into the early morning hours of Sunday. .LONG TERM...(Sunday through Saturday) Issued at 306 PM EST SAT JAN 6 2024 Key Messages: -We transition into an active pattern next week, bringing with it a couple opportunities for widespread snow. How much will depend on the track of the system`s producing these. -Deepening low pressure over the Plains will move into the Great Lakes Tuesday night and Wednesday, bringing with it the potential for accumulating system/lake enhanced snowfall and gusty winds. -Another system will be possible Thursday/Friday. The main item of interest in the long term period will be the transition from our benign winter pattern so far, to a more active pattern across the Great Lakes region, resulting in a couple opportunities for snow. For some time now, guidance has suggested a couple deep troughs over the southern Plains/Rockies will kick out and lift northeast a couple different lows next week, potentially interspersed with a weaker low/shortwave/clipper trying to dig into the Northern Plains and middle Mississippi River Valley. Last night`s 0z and today`s 12z guidance continues to suggest a similar pattern. It should be noted that with this pattern, snow accumulations will depend on system track. At this point, there is still a notable amount of uncertainty in their trajectories, so continued monitoring of the forecast is recommended for next week. Beginning Sunday, a shortwave trough and clipper surface low will press west to east through Lake Superior, pulling a cold front through our forecast area. Frontal forcings and upper level dynamics are lacking with this system and mostly confined closer to the surface low. The post frontal airmass, characterized by 850mb temps falling to around -9C atop a +4 or +5 degree lake surface, should be enough to yield a brief round of lake effect snow though, mainly in the Keweenaw and the eastern UP. Dry air and increasing subsidence aloft though should work to lower inversion heights and erode shower activity through the day, which will limit snow accumulations. Both NBM and HREF snow probabilities highlight this well, indicating the highest amounts are likely to be confined to the Spine of the Keweenaw, perhaps upwards of 2 inches by the end of the day and mostly in the morning hours. Less is expected elsewhere, with perhaps isolated amounts approaching an inch in the eastern northwest wind snow belts, mostly in the afternoon hours. Brief surface ridging emanating southeast from a high over Saskatchewan will result in a quiet Sunday night with lows in the teens interior and near 20F by the lakeshores. This high slides southeast through our forecast area during the day Monday as a deep trough moves out of the southern Rockies and surface cyclogensis begins in the Texas/Oklahoma/Colorado region. With this, a dry Monday with highs in the upper 20s or low 30s is expected. As the trough presses eastward and begins taking on a negative tilt, the surface low will deepen as it lifts northeast into the Ohio River Valley and Great Lakes region Tuesday into Wednesday. Increasing q- vector convergence and isentropic lift will precede the low, allowing a mix of ptypes to lift northeast, then wrap around the low and cool into snow as it moves toward the low`s deformation axis. Those caught on the southern and eastern side of the system should expect mostly rain, but those on the northeast side should expect a mix of ptypes before transitioning to all snow along the low`s northern flank. The GEFS and EC ensemble systems have consistently positioned the UP to the northern or northwestern side of the system within the deeper cold air while the low tracks through Lower Michigan. This has checked well against previous GFS and EC deterministic runs as well. These solutions would yield lake- enhanced snow with an upslope component for the northeast snow belts Tuesday and Wednesday, with maybe light to moderate system snow in areas near Lake Michigan and the east if the precip shield extends far enough north. The most recent NAM has trended north, bringing the low through northern Lake Michigan and positioning the UP in the ideal position for widespread system snow. When considering other 12z guidance though, this appears to be an outlier save for the EC`s precip shield`s northward extent. At this point, leaning toward a more northward spreading precip area, mixing in both the lake enhanced and system snow option. Greatest areas of concern for this scenario will be along the Lake Michigan lakeshores from Menominee through Schoolcraft counties, Luce County, and the northeast snow belts of Alger County and west of Marquette in Marquette County. Snow probabilities among the various ensemble systems suggest these areas are most likely (50% or higher) of exceeding 3 inches. With the surface low deepening as it moves through the Great Lakes, increasing pressure gradient will yield gusty winds, particularly near the lakeshores and in the central/eastern UP. Depending on its depth, northeast and northerly gusts upwards of 30 mph, with higher gusts near the lakeshores, will be possible. Weak ridging will follow Wednesday night, but erodes quickly as a weak shortwave lifts northeast out of the Plains and a clipper presses east across the Dakotas. Previous runs had both weakening on their approach, but 12z guidance suggests the clipper may weaken while reinforcing the low from the southeast. In either situation, the colder airmass overhead coupled with forcings from either should be able to yield additional widespread light snow Thursday/Thursday night. It should be noted that there is some potential that this could be a sneaky and overachieving system. EC and GEFS ensemble meteograms show a couple members at various sites in the UP yielding 2-4 inches. At this point though, I`d say the probability of this is low (<25%), but is something to watch as we move into next week. As Thursday`s event unfolds over the region, another deep trough is expected to dig into the Intermountain West/Four Corners region. Much like the mid-week system, as it ejects into the Plains, a surface low with ample access to Gulf of Mexico moisture will develop and lift northeast. It is certainly way to early to speak with much confidence about the track of this system, but anyone with weekend plans should monitor the forecast for updates. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 640 PM EST SAT JAN 6 2024 The -sn that was over the area today continues to diminish, leaving behind MVFR to IFR conditions. A cold front will move across the area on Sun, bringing some lake effect -shsn. At IWD, expect MVFR to prevail tonight. Cigs may bounce around to VFR at times, but vis should remain MVFR in br with some -sn/flurries also possible. Wind shift to nw Sun morning at IWD should bring cigs down to IFR with ocnl -shsn as well. MVFR will prevail for Sun aftn. At CMX, IFR should mostly prevail tonight. While cigs may bounce around to MVFR or even VFR at times, vis should remain IFR in br and ocnl -sn. Wind shift to nw will occur early Sun morning with an increase in -shsn. Expect improvement to MVFR by late morning at CMX with MVFR then continuing thru the aftn. At SAW, IFR should prevail thru the night, though cigs may occasionally bounce around to MVFR or VFR at times. Passage of cold front Sun morning will bring improvement to prevailing MVFR. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 306 PM EST SAT JAN 6 2024 Winds should weaken tonight below 20 knots lake-wide. A cold front pressing through the lake tomorrow will result in increasing colder air aloft and wind gusts from the northwest. Raw guidance suggests wind gusts mostly in the low 20s, but model soundings show some higher gust potential within the boundary layer. With this in mind, trended the winds on the higher end of guidance into the upper 20s. With the lake commonly overachieving with these sorts of clipper events, I suspect some low 30 knot winds will even be possible across the east half Sunday for high reporting platforms. Light winds should prevail Sunday night and Monday with high pressure sliding through the region. A strong system is expected to lift into the Great Lakes Tuesday into Wednesday. Ahead of the low, increasing southeasterly winds to 20-30 knots are expected Monday night across the east near the international border. As the low approaches the region Tuesday, these stronger winds will spread across the lake as winds shift to the northeast. These strong winds will persist Wednesday, when the strongest pressure gradient is expected. Some gales will be possible, mainly across the east half. Recent EC probabilistic guidance suggests 50-70 percent gusts could exceed 34kts Wednesday. If this trend continues, a gale watch may be needed in future forecast packages. Another system may follow Thursday night/Friday that could again result in increased winds in the 20s or near 30kts. Beyond this, the most notable feature is a potential strong storm next weekend somewhere the Great Lakes. With this system being so far out and confidence on a track being very low (<10%), its advised to continue monitoring the forecast if transiting any of the Great Lakes this weekend. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...LC LONG TERM...JTP AVIATION...Rolfson MARINE...JTP
Area Forecast Discussion
National Weather Service Spokane WA
351 PM PST Sat Jan 6 2024 .SYNOPSIS... A weather system will continue to bring light to moderate precipitation in Eastern Washington this afternoon and through tomorrow (Sunday) morning in North Idaho. A cooling trend is likely next week along with additional chances for snow. && .DISCUSSION... ...Heavy Cascade Snow, Locally Windy, and Trending Much Colder Next Week... Today through Sunday: A Puget sound convergence zone has developed and is aimed at Stevens Pass early this afternoon aided by WNW winds aloft and even decent surface instability on the west side. Surface temperatures in the lowlands on the west side are in the low to mid 40s and 500 mb temperatures are around -35C. Talk about some steep lapse rates. Short term RAP guidance indicates low to mid level winds will turn NNW to nearly north in the early evening hours, shutting down the convergence zone for our area. An additional 2 to 5 inches of snow may fall at the crest through early this evening. Central Washington has remained quite warm and precip free through early this afternoon thanks to downsloping winds. Eastern Washington has been stubborn to clear out. I think its due to an established surface low that formed east of the Cascades. Fairchild AFB has the lowest surface pressure east of the Cascades and visible satellite even shows a small comma head just west of the AFB. High resolution models have struggled with the evolution of this surface low leading to a tough forecast. Snow levels turned out to be a larger issue than previously thought as well with locations downtown being just wet (so they are higher than I originally thought). 500 mb temperatures in eastern WA/north ID are still cooling off, but it appears the precip shield is benefiting from this as precipitation intensities have held on. The bulk of the precip should be departing Eastern Washington in the next few hours, so highlights will be taken down. Some light snow still may occur but road conditions appear to be good in the region, so it is not a major concern. North Idaho will hang on to higher precip chances through the evening since the surface low is still in Eastern WA, so the advisories will be kept for now. Temperatures will begin to fall into the upper to mid 20s, ensuring cold enough air for snow everywhere in north ID. Additional light snow is expected through tomorrow in the ID Panhandle but is not headline worthy. This was a tough forecast. db Monday through Friday: A Winter Storm Watch has been issued for much of the region as the next system continues to trek across along the Canadian coastline. The Watch expands over a period of 2 days, meaning that the snow will accumulate between Monday and Wednesday morning. The Cascades will see the heaviest snowfall, with accumulations upwards of 2 to 4 feet during this period, with rates in excess of 2 inch per hour around Tuesday morning. The valleys are a big trickier, as temperatures will be hovering right around freezing for daytime highs. The Columbia Basin and Okanogan Valley will see the lightest snow, with anywhere from a trace to 3 inches. Eastern Washington will see 4 to 8 inches of snow, but ensembles are indicating that there is a potential for some localized higher amounts. For the ID Panhandle, the snow amounts increase again, with widespread 8 to 12 inches in the valley locations, including CDA. On top of the snowfall, we are also going to see some increased winds in the Columbia Basin, Palouse, and Spokane area on Tuesday. Gusts up to 50 mph are expected. While temperatures will be around freezing, visibilities will be significantly reduced due with the snow and rain combination. Another system will slide into the region, following a similar path to the first two. This storm will bring additional snow to the Cascades . This could change as we move closer to the end of the week as there is quite a bit of uncertainty in the ensembles. High temperatures will be near freezing to start out the week with cooling temperatures beginning as early as Wednesday. Ensembles continue to hint at big changes arriving temperature wise with the potential for highs in the teens and lows in the single digits above or below zero. There is some variation in the ensembles, so stay tuned as we get closer to the end of next week. /KM && .AVIATION... 00Z TAFS: MVFR and occasionally IFR cigs and visibility continue to be the main concern in Eastern WA/North Idaho for the next 24 hours. Rain and snow showers will impact KPUW-KGEG-KSFF-KCOE through 03z as well potentially bringing very brief visibility reductions. After 03z, snow shower activity will be limited to the Idaho Panhandle. VFR conditions will prevail in central WA but KEAT will remain breezy this evening. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence for MVFR cigs and visibility in E WA/N ID. Lower confidence in ceilings behind the last round of rain and snow showers especially in eastern WA/North ID. ------------------ Confidence descriptors: Low - Less than a 30 percent chance Moderate - 30 to 70 percent chance High - Greater than a 70 percent chance For additional probabilistic information for NWS Spokane airports, please refer to the Aviation Dashboard on our webpage: https://www.weather.gov/otx/avndashboard && .PRELIMINARY POINT TEMPS/POPS... Spokane 26 32 21 32 30 35 / 30 30 0 80 90 90 Coeur d`Alene 26 31 20 31 29 34 / 60 40 10 80 90 100 Pullman 27 32 23 32 30 36 / 40 40 10 70 100 100 Lewiston 31 40 28 39 36 42 / 40 30 0 50 90 90 Colville 24 33 15 27 24 31 / 60 30 0 80 90 90 Sandpoint 23 33 19 29 28 30 / 70 80 30 90 100 100 Kellogg 26 31 23 31 30 34 / 80 70 50 80 100 100 Moses Lake 27 39 25 33 31 40 / 10 0 0 70 70 60 Wenatchee 28 38 27 32 31 38 / 10 0 0 70 80 80 Omak 27 33 20 32 30 33 / 20 0 0 70 90 80 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...Winter Weather Advisory until 4 AM PST Sunday for Central Panhandle Mountains-Coeur d`Alene Area-Idaho Palouse- Northern Panhandle. Winter Storm Watch from Monday morning through Wednesday morning for Central Panhandle Mountains-Coeur d`Alene Area-Idaho Palouse-Northern Panhandle. Winter Weather Advisory until 4 AM PST Sunday for Lewis and Southern Nez Perce Counties. WA...Winter Weather Advisory until 4 AM PST Sunday for Northeast Blue Mountains-Northeast Mountains-Okanogan Highlands-Spokane Area-Upper Columbia Basin-Washington Palouse-Western Chelan County. Winter Storm Watch from Monday morning through Wednesday morning for Northeast Mountains-Okanogan Highlands-Spokane Area. Winter Storm Watch from late Sunday night through Wednesday morning for Central Chelan County-Western Chelan County- Western Okanogan County. && $$