Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/23/21

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
912 PM CST Fri Jan 22 2021 .UPDATE... Issued at 910 PM CST Fri Jan 22 2021 No major changes made to the forecast tonight. Timing for snow moving in late tonight/early Saturday morning still looks good, as well as placement of Winter Weather Advisory headlines. && .SHORT TERM...(This Evening through Saturday Night) Issued at 338 PM CST Fri Jan 22 2021 Low clouds have moved to the east of the James Valley this afternoon and will continue to move out of the CWA into the evening hours. Otherwise, for tonight and Saturday, we are still on track for accumulating snowfall across most of the CWA. A shortwave trough ejecting out of the southwest U.S. upper trough and across our region through Saturday night will be the main influence in bringing the snowfall. Also, the confluence of the southwest and northwest airstreams over South Dakota will be the other big influence on the lift for snowfall. A northwest to southeast xsct through South Dakota shows the greatest deep layer lift mainly across our far southern CWA and across southern South Dakota. WAA increasing tonight along with mid level frontogenesis will provide good lift in the snow growth zone into Saturday. The lapse rates were favorable from 700-500H in the 7 to 8 degree C range. Also, the RR quadrant of a jet streak to our northeast will provide good upper divergence for lift. Therefore, all models and ensembles point to snow developing after midnight in our southwest CWA, then spreading northeast through Saturday. The northern edge of the snow will still be tricky with north central SD looking to get little to no snowfall. The Winter Weather Advisory still looks fine, extending from southwest SD into northeast SD/west central MN later tonight into Saturday night where 2 to 5 inches are expected. The system will move out quickly Saturday evening with colder air pushing in on north to northeast winds. Don`t expect much for blowing snow with this system. .LONG TERM...(Sunday through Friday) Issued at 338 PM CST Fri Jan 22 2021 The extended period looks pretty inactive overall. The period starts out with polar high pressure centered over southern Saskatchewan/Manitoba and nudging down into the Dakotas and Minnesota. The surface high doesn`t move much through the first half of next week and results in below average temperatures through Tuesday. The one question in regards to precipitation is presently Tuesday night. Deterministic solutions are consistent in low pressure developing over the Central Plains Tuesday and pushing off to the northeast Tuesday night through Wednesday. That said, latest model guidance maintains a system that either grazes the southern forecast area or keeps it south altogether. Either way, it`s still Day 5, so just something to monitor for now. && .AVIATION...(For the 00Z TAFS through 00Z Saturday Evening) Issued at 525 PM CST Fri Jan 22 2021 Terminals KABR,KATY,KPIR,KMBG VFR conditions will prevail across the area tonight. An area of snow, accompanied by IFR/MVFR cigs and MVFR vsbys, will spread from southwest to northeast on Saturday. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...Winter Weather Advisory from 3 AM Saturday to midnight CST Saturday night for SDZ018>023-035>037-045-048-051. MN...Winter Weather Advisory from 3 AM Saturday to midnight CST Saturday night for MNZ046. && $$ UPDATE...Parkin SHORT TERM...Mohr LONG TERM...Telken AVIATION...Parkin
Area Forecast Discussion
National Weather Service Caribou ME
1100 PM EST Fri Jan 22 2021 .SYNOPSIS... Low pressure will cross the region overnight. Low pressure will then remain across the Maritimes Saturday through Monday. High pressure will build toward the region Tuesday into early Wednesday as low pressure passes well south of the region. && .NEAR TERM /THROUGH SATURDAY/... 11:07 PM Update: Light snow persists in northeastern parts of our area supported by a weak inverted trough over the region. The light snow will continue for a couple hours then dissipate to snow showers as the trough moves away. Updated forecast to reflect this and adjusted temps a bit. Previous discussion: Tonight...WAA continues w/light snow occurring across the northern and western areas w/radar showing echoes weakening as the sfc low pres weakens this evening as it lifts ne. Further s, pretty quiet w/the regional radar showing some development of light snow across swrn areas pushing ne. An inverted trof extending back from the low e of Nova Scotia will act as a focus mechanism for more snow with radar filling later tonight. The steadiest snow will be across the northern 1/2 of the CWA as a vigorous vort max provides the available lift for the light snow. Additional inch or so of snow is expected w/this feature. Across srn areas, an upper disturbance will move across the Gulf of Maine waters w/precip expanding as it interacts w/the inverted trof at the sfc. The latest HRRR and RAP were aligning well w/this setup and show the precip shield to the s expanding back toward the coast w/the far eastern side of Washington County seeing some enhancement, as does the NMM and WRF. But, these two sets of guidance have been overdoing the current activity. The ECMWF has been very consistent w/showing this feature but the 12z run did shift the precip shield a bit further s, matching closer to the 12/18z NAM. Therefore, decided to show a nose of enhanced precip moving into the coast and Washington County w/potential of an additional inch or so of snow by early Saturday morning. Above normal temps for tonight. For Saturday, light snow in the morning will be transitioning to snow showers as the upper trof swings through and forcing weakens. Some CAA coupled w/a gusty NW flow off the open St. Lawrence will set the stage for the potential for some snow showers and perhaps streamer activity across the mtns and nrn areas. Plus, a fairly potent vorticity max is forecast to slide se across the region helping to trigger the snow shower/streamer activity. Not expecting much additional accumulation from this activity. NW winds will be picking up though w/sustained winds of 10-20 mph w/gusts up to 30 mph. Daytime temps near to slightly above normal. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... Saturday night into Sunday will be marked by windy conditions generated by a tight pressure gradient between a large low pressure complex in the Maritimes/North Atlantic and a sprawling high pressure system over large portions of Canada and the eastern US. Warmer air aloft will actually be wrapping around the closed upper low from Labrador and northern Quebec into the forecast area. This will generate clouds and snow showers Saturday night and Sunday...mostly in northern zones. No appreciable snow accumulations are expected and these warm air advection events from the north usually don`t produce much. Wind chills will be below zero for much of the area Sunday morning and wind gusts will reach up to 30 mph on Sunday. The winds will gradually decrease Sunday night into Monday as the low in the Maritimes moves out and high pressure builds. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... A large dome of high pressure over most of Canada and the northern tier of the US builds Monday night and dominates through Friday. The storm track will be well south of the area. In general, temperatures look to be slightly above normal, but have some concerns that nighttime model temps may be a bit warm at night for areas with snow cover in northern zones. Went for lower temps than guidance on Monday night. Did add some PoPs for Tuesday night into Wednesday for another weak upper disturbance rotating south from northern Quebec. This is primarily shown by the ECMWF and confidence in this feature is not very high. Again, any snowfall would be light. At this point, this January ranks as the 4th least snowy on record at Caribou and there`s not much on the horizon to suggest that`s going to change appreciably. && .AVIATION /04Z SATURDAY THROUGH WEDNESDAY/... NEAR TERM: Predominately MVFR at the northern terminals overnight in lower clouds and occasional light snow. Very brief IFR visibility restrictions are possible. VFR for KBGR and KBHB with a period of MVFR with isolated to scattered snow showers possible after midnight. Light and variable wind less than 10 kts becoming NW by early Saturday morning at 10 kt. For Saturday, MVFR continues for the northern terminals in light snow/snow showers. VFR for KBGR-KBHB. NW winds increasing to 10-15 kt w/gusts to AOA 25 kt. SHORT TERM: Saturday night into Sunday...MVFR tempo IFR in snow showers north of HUL and GNR. VFR elsewhere. NW winds gusting to 30 kt. Sunday night into Tuesday...VFR with light NW winds Tuesday night into Wednesday...MVFR tempo IFR in snow showers north of HUL and GNR. VFR elsewhere. Light NW winds. && .MARINE... NEAR TERM: Light winds WNW less than 10 kt increasing to 10-15 kt late tonight. Seas 1-2 ft, slowly building to 2-3 ft by morning. For Saturday, a Gale Warning as been posted for late Saturday into Sunday including the intra-coastal zone. NW Winds will be increasing to 20-25 kt w/gusts increasing to 35+ kts. Seas will build to 3-4 ft. SHORT TERM: Gale conditions are expected Saturday evening into Sunday evening...followed by SCA conditions into Monday evening. && .CLIMATE... Month to date it has been the 2nd warmest January and 13th least snowy January on record in Caribou, Maine. Weather records date back to 1939. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...Gale Warning from 5 PM Saturday to 4 PM EST Sunday for ANZ050>052. && $$ Near Term...CB/Hewitt Short Term...MCW Long Term...MCW Aviation...CB/Hewitt/MCW Marine...CB/Hewitt/MCW Climate...CB
Area Forecast Discussion
National Weather Service Cleveland OH
1016 PM EST Fri Jan 22 2021 .SYNOPSIS... High pressure will build east across the Great Lakes Saturday and Sunday. Low pressure will move northeast through the Ohio Valley Monday into Tuesday with mixed wintry precipitation. && .NEAR TERM /THROUGH SATURDAY NIGHT/... The flow across Lake Erie has shifted to more northwesterly this evening with lake effect snow showers extending farther inland across the snowbelt of NE Ohio. This has allowed for a weakening trend although expecting light snow to continue for portions of the overnight with moisture extending into the shallow dendritic growth zone. A light powdery snow will be focused across favored upslope areas, although single digit dewpoints spreading southeast across Lake Erie will prove to be a limiting factor as we progress through the night. For Northwest Pennsylvania, lake effect snow bands seen in SW New York are expected to shift westward with time into eastern portions of Erie and Crawford Counties. These areas will see an uptick in snow overnight with an additional 1 to 4 inches expected while areas closer to the Ohio State line will see snow shower activity decrease. The uncertain part of the forecast remains the location of any more dominant band extending from Lake Huron later tonight. Generally expecting enough movement of this band that we did not issue an advisory but will need to be monitored overnight. Previous discussion... Lake effect snow continues across Northeast Ohio and Northwest Pennsylvania this afternoon as another trough axis swings east across Lake Erie. Snow intensity has increased slightly over the past couple of hours, especially in Lake, Geauga and Ashtabula Counties, prompting two lake effect special weather statements highlighting the gusty winds and reduced visibilities. Satellite and radar trends suggest some of this snow is being enhanced by an upstream connection from Lake Michigan and perhaps even as far north as Lake Superior. Increased snow totals over the Lake/Geauga/Ashtabula areas by about an inch or two through the next 6 hours. Hires guidance from the HRRR suggests that low- level moisture will be sufficient to sustain moderate lake effect snow through at least 7 PM this evening. Will have to monitor trends to see if a short-fused advisory is warranted for Lake/Geauga/Ashtabula. Otherwise, as the trough swings east across the lake, flow aloft becomes more northwest to north, with lake effect snow primarily transitioning to Northwest Pennsylvania. In particular, will have to keep an eye on southern Erie County to see if an upstream connection to Lake Huron occurs. Did not have enough confidence to go with an advisory at this point for southern Erie, but if the upstream connection develops, an advisory will likely be needed overnight through tomorrow morning. High pressure builds in later on Saturday, with height rises and drier air signaling an end to any residual lake effect snow across Northeast Ohio and Northwest Pennsylvania. Areas west of I-77 may have a decent shot at seeing sunshine during the day as high temperatures reach the upper 20s to lower 30s. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... Generally quiet early Sunday as high pressure just to the east moves farther east and cloudiness increases as warm advection overspreads the region. There is a slight chance of light snow or perhaps mixed wintry precipitation late in the day south of US Route 30. On Sunday night moisture will continue to increase and there is a slight chance again of light snow possibly mixed with freezing rain generally south of US Route 30. Northeast Ohio and nw PA should remain dry. On Monday mixed wintry precipitation with just snow on the northeast edge will spread into the area but timing differences appear as the GFS is more progressive(faster)than the ECMWF short wave over the Mississippi Valley. The NBM pops have been used which could be too low if the recent run of the GFS is correct. On Monday night the low pressure area will be moving across the Ohio Valley just south of the region and allow enough warm air aloft for mixed wintry precipitation to prevail across the region. The GFS is faster with the movement of the system and thus colder on the backside of the system but will lean toward the slower Euro which is more consistent with the NBM data. && .LONG TERM /TUESDAY THROUGH FRIDAY/... The upper low will exit the region Tuesday evening with light mixed wintry precipitation ending as snow showers Tuesday afternoon. The southern stream jet persists across the country through the remainder of the period with generally zonal flow with somewhat of a repeat of the pattern with a system passing by to the south of the region. The pattern is slightly colder and drier with little precipitation expected in the form of snow showers. High temperatures will be below normal from the upper 20s to lower 30s. Lows will be in the teens to lower 20s. && .AVIATION /00Z Saturday THROUGH Wednesday/... Lake effect snow showers will continue across portions of the Ohio and Pennyslvania snowbelt overnight and will be most likely to impact YNG this evening and ERI after 06Z although could briefly clip CLE. Visibilities could drop to a mile or less in the heavier snow showers but that will be short lived at any terminal. Otherwise ceilings will range from MVFR to VFR overnight and expecting to start to see some clearing developing across NW Ohio between 04-06Z with an eastward expansion into Saturday. Winds will become more northwesterly with time and some gusts to 20 knots may continue overnight at terminals near Lake Erie. Outlook...Non-VFR possible once again with snow Sunday night through Tuesday, some mixed precipitation is possible Monday. && .MARINE... Northwest flow prevails across the region with a weak surface trough persisting across the lake. Cold advection is allowing northwest winds generally of 15-22 knots with higher gusts to mix to the surface and this will likely continue into Saturday afternoon. High pressure over the Iowa will gradually build east over the lake by Saturday evening and allow winds to slacken. The high pressure area will remain just northeast of the region into Sunday night as low pressure develops over the Ozarks. The low pressure area will move northeast into the lower Ohio Valley Monday afternoon and upper Ohio Valley by Tuesday morning. Northeast winds will increase early Monday and a small craft advisory is likely that will persist through Tuesday. The surface low will move off the Mid-Atlantic coast by Wednesday morning as high pressure persists north of the lake. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. MARINE...Small Craft Advisory until 4 PM EST Saturday for LEZ147>149. Small Craft Advisory until 10 AM EST Saturday for LEZ145-146. && $$ SYNOPSIS...Kahn NEAR TERM...KEC/Kahn SHORT TERM...LaPlante LONG TERM...LaPlante AVIATION...KEC MARINE...LaPlante
Area Forecast Discussion
National Weather Service Corpus Christi TX
551 PM CST Fri Jan 22 2021 .AVIATION... Expect a transition to IFR/LIFR ceilings and MVFR/IFR visibilities overnight/early Saturday morning followed by IFR/MVFR ceilings and VFR visibilities during the late morning/afternoon Saturday. Brief MVFR visibilities near isolated showers, mainly Saturday afternoon over the Coastal Plains. Generally weak onshore flow overnight/early Saturday, followed by weak to moderate Saturday afternoon. && .PREV DISCUSSION... /Issued 253 PM CST Fri Jan 22 2021/ SHORT TERM (Tonight through Saturday Night)... Afternoon satellite and surface data revealed a diffuse boundary stalling offshore ahead of subsidence and drying aloft. Surface dewpoints behind this boundary have remained largely unchanged, and actually risen in some areas. This will help set the stage for stratus and fog development later tonight as ENE winds pull deeper moisture onshore. Although the odd model out, the NAM is now slower in veering northerly winds to the east (thanks to drier surface ridging arriving from the N TX) and as a result has considerably less fog overnight compared to the SREF, HRRR and RAP. This lends uncertainty to widespread dense fog development, although later shifts will monitor trends for a possible Dense Fog Advisory. Stratus overnight will gradually thicken through the day on Saturday as moist isentropic ascent improves ahead of a developing warm front. Even though models trended drier with PoPs for Saturday, afternoon soundings across the Coastal Plains depict low stratus thickening to at least 2000 feet which is usually a good threshold for some drizzle or very light rain development. However, PoPs were shaved back to just slight chance as much of this activity may only produce a trace at best of precip. High temps tomorrow were lowered a good 3-7 degrees below the suspiciously mild NBM for this otherwise cloudy and cool easterly flow regime. Additional PoPs remain intact Saturday night as the warm front lifts north across the region, yet soundings still show saturated layers confined to the lowest 2-4k feet beneath the EML/capping layer, so only light rain or drizzle remains in the offing. LONG TERM (Sunday through Friday)... A deep trough over the desert Southwest will shift easterly over the Southern Great Plains early next week, bringing a cold front through the area late Sunday night into Monday morning. Models have slowed the progression of the front lately, with the NAM being the slowest showing the front reaching the coast around noon. In advance of the front, isolated showers are possible as low-level moisture remains high with PWAT values around 1.5". However, a strong cap is in place on Sunday behind the warm front with warm dry southwesterly flow above 850mb remaining in place. In addition, CIN values are well into the triple digits, with much of the area less than -300 J/Kg. Due to this combination, have removed thunderstorm potential and have limited activity to isolated light showers with the aid of isentropic lift across the Coastal Plains and Victoria Crossroads Sunday. As the weak cold front approaches the area late Sunday night into Monday morning, a similar situation is in place; isolated showers are possible for the Coastal Plains and Bend but thunderstorm chances remain silent as energy aloft remains focused north and east of the area. Models have also been trending drier and therefore have decreased PoPs from the NBM. Drier conditions and high pressure take over in wake of the front, persisting through Tuesday night ahead of the next weak cold front passage on Wednesday. Rain chances remain only slight on Wednesday for the Coastal Bend and waters as a surface trough over the northwest Gulf of Mexico prohibits sufficient moisture advection with PWATs below 0.75". Dry conditions return Thursday for all areas. In regards to temperature, Sunday will be the warmest with highs in the upper 70s to mid 80s and lows in the 60s due to strong southerly warm air advection and clouds at night. Otherwise, highs are expected to remain in the 70s through the extended with lows in mid 40s to mid 50s. MARINE... Northeast winds will remain weak tonight before turning easterly on Saturday and increasing to weak to moderate ahead of a warm front. Sea fog is likely later tonight into Saturday morning before dissipating in the afternoon. Dense fog is possible. Occasional light rain or drizzle should develop Saturday through Saturday night ahead of weak to moderate southeast flow overnight. Additional sea fog is expected Saturday night, lingering over the bays and nearshore waters through Sunday morning. Moderate onshore flow Sunday morning will strengthen to moderate to strong in advance of a cold front passage early Monday morning. Small Craft Advisory conditions with seas building to near 10 feet are likely Sunday night into Monday. Winds then weaken to moderate and rotate counter clockwise through the day Monday, becoming northeasterly by Monday night. Moderate north to northeasterly flow persists through Thursday with another cold front passage on Wednesday. Small Craft Exercise Caution conditions are possible Wednesday through Thursday for the offshore waters. Isolated showers are possible Sunday through Monday, and then again on Wednesday in association with the fronts. && .PRELIMINARY POINT TEMPS/POPS... Corpus Christi 59 67 64 78 65 / 10 20 20 20 10 Victoria 58 68 62 77 63 / 10 30 30 30 20 Laredo 59 70 66 84 61 / 10 10 10 10 10 Alice 57 68 64 83 64 / 10 20 20 20 20 Rockport 57 66 63 73 64 / 10 20 20 20 20 Cotulla 57 67 63 81 60 / 0 10 20 10 20 Kingsville 58 68 64 82 65 / 20 20 20 20 10 Navy Corpus 60 67 66 73 65 / 10 20 20 20 10 && .CRP WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ WC/87...AVIATION
Area Forecast Discussion...Update
National Weather Service Hanford CA
518 PM PST Fri Jan 22 2021 ...Update to Air Quality Issues Section... .SYNOPSIS...A low pressure system will bring periods of light rain and mountain snow to the area through early Saturday as it moves across central California. A colder system will bring precipitation to the area Sunday night and Monday. A potentially strong storm will bring moderate to locally heavy precipitation to the area on Wednesday and Thursday. && .DISCUSSION...The first of a series of at least three storm systems is now impacting our area as an upper low which was off the PAC NW coast yday is now centered over the SF Bay Area as depicted by satellite imagery. As the associated trough deepened over our area today, the airmass over our area has become unstable enough for showery precipitation to spread southward into our area with several spotters in the San Joaquin Valley reporting ice pellets and radar imagery indicating some fairly strong (50 to 55 dBz) reflectivities. The convection itself is low based and very shallow, but would not be surprised if a thunderstorm or two briefly pops up in the valley this afternoon. Mesowest indicating the snow level has been running from around 4000 feet near Yosemite Park to around 5000 feet in Tulare County. We expect the showery precipitation to continue through this evening then taper off overnight as the HRRR is indicating the low will drop southward to the Socal coast overnight the push inland south of our area on Saturday. The low is progged to move east of our area by Saturday night which in a dry period across our area Sunday night and Sunday morning with brief shortwave ridging. The second storm is progged to push southward into our area on Sunday evening and bring a period of significant precipitation to our area Sunday night and Monday. This system is also expected to have more moisture with it than today`s system and we are anticipating liquid equivalents of half and inch to an inch and a quarter of liquid precipitation over the Sierra Nevada with this system and a quarter to three quarters of an inch of liquid precipitation over the Kern County Mountains. This second system is also expected to be much colder with snow levels lowering to 1500 to 2500 feet by Monday afternoon. The main concern with this second system will be snow at lower elevations that could adversely impact travel over the mountains. Between 6 and 12 inches of snow are expected above 4000 feet in the Sierra Nevada and between 3 and 6 inches of snow above 3000 feet in the Kern County Mountains which would impede travel over the Tejon, Tehachapi and Walker passes. With impacts to travel being a concern we have issued a Winter Storm Watch for the Sierra Nevada and the Mountains of Kern County from 1000 pm PST Sunday evening until 400 pm PST Monday afternoon. This second system will move out of our area by Tuesday morning. Mother than some residual Mountain showers, Tuesday should be a dry and chilly day across our area. Temperatures across much of the San Joaquin Valley will likely be below the freezing mark for a few hours on Tuesday morning. That sets up the stage for the third storm which is expected to be the strongest system to impact our area in several months on Wednesday and Thursday. Confidence is improving in that it will spread widespread precipitation into our area by Wednesday morning and pick up some subtropical moisture Wednesday night and Thursday. The NBM is indicating that this system could produce 1.5 to 3 inches of rain in the San Joaquin Valley and 4 to 6 inches of liquid precipitation in the Sierra Nevada on Wednesday and Thursday. There is some uncertainty on where the snow level will be with this system as any subtropical moisture that gets pulled up will likely mean higher snow levels and increased potential for runoff and possible flooding concerns. This storm will move out of our area by Friday, but cyclonic flow behind it will likely maintain a chance of showers across our area. && .AVIATION...Areas of MVFR and local IFR in low clouds and showers over the San Joaquin Valley, West Side Hills and Sierra foothills. Widespread mountain obscuring IFR over the Sierra Nevada in low clouds and snow showers. Increasing areas of IFR over the Tehachapi Mountains after 03Z Sat becoming widespread mountain obscuring IFR by 06Z Sat in low clouds and showers. Otherwise, VFR conditions will prevail over the central CA interior during the next 24 hours. && .AIR QUALITY ISSUES... On Saturday January 23 2021... Fireplace/Wood Stove Burning Status is: No Burning Unless Registered in Fresno County. Further information is available at && .CERTAINTY... The level of certainty for days 1 and 2 is medium. The level of certainty for days 3 through 7 is medium. Certainty levels include low...medium...and high. Please visit for additional information an/or to provide feedback. && .HNX WATCHES/WARNINGS/ADVISORIES... Winter Storm Watch from Sunday evening through Monday afternoon for CAZ192>197. && $$ public/aviation/fw...DS pio/idss...DCH
Area Forecast Discussion
National Weather Service Marquette MI
709 PM EST Fri Jan 22 2021 .SHORT TERM...(This evening through Saturday) Issued at 351 PM EST FRI JAN 22 2021 Very broad upper-level troughing covers all of the Great Lakes and eastern Canada this afternoon. With 850 mb temps around -21 C, lake effect snow showers continue in the NW wind snow belts of the east half. However, MSAS analysis shows surface high pressure centered over Iowa extending a ridge northward over western Lake Superior. Low-level drying with this surface ridge (plus subsidence with mid- level height rises) has allowed cloud cover to begin clearing from south to north. As the low levels dry out, lake effect snow showers have ended around Ironwood and diminished to mostly flurries over the Keweenaw. Temps have been steady in the upper single digits and low teens throughout the day and it seems that little bit of sunshine hasn`t helped at all. Tonight, NW flow aloft will continue and the surface ridge will slide by to the south through Wisconsin and into northern Illinois. A fast-moving short wave currently seen in water vapor satellite over southern Alberta will reach western Lake Superior by about 09z tonight just as the low-level flow is becoming SW over the western U.P. The combination of lift from this wave and SW flow with enhanced landbreezes will induce a convergence band over western Lake Superior. This band will take full advantage of lake sfc-850 mb delta T`s around 19-20 C and saturation to around 7 kft to produce a classic "Bayfield Bomber" lake effect snow band across the western half of the lake and into the Keweenaw. This will be the main story of this short-term period. HRRR and other high-QPF CAMs have been verifying well in this regime with multiple lake-effect events over the past week, so with such a strong convergence signal and such favorable parameters, felt confident to lean high on QPF. The slight warming aloft will actually be a net positive for SLRs as it means the DGZ will be thicker and overlap more with the low-level omega. Therefore, SLRs > 20:1 are likely. The end result is a narrow band of 6-12" of snow from about Twin Lakes north to about Delaware. The exact placement will determine who sees how much snow, but it is possible that this band stalls in one area long enough to produce 12"+ of snow. Right now the best bet for seeing those high-end amounts would be north of Calumet and southwest of Eagle River. Have issued a new Winter Weather Advisory for Keweenaw and northern Houghton counties for tonight and tomorrow. Amounts could justify a warning but the small areal coverage of high amounts does not. The eastern Winter Weather Advisory segment remains in effect through 05z as previously scheduled. There is some concern that the end of the aforementioned strong convergence band will reach the eastern shoreline around Melstrand or Grand Marais. If it did, there could be several inches more over a small area after midnight tonight, but confidence in that happening is not particularly high. As for temps tonight, it`s going to be a cold one. Lows should fall into the single digits below 0 across the interior, although the arrival of mid-level clouds overnight should keep temps from getting even colder. Tomorrow, continued height rises and WAA aloft will lead to warmer temps. There could even be some sunshine across the west half. This will lead to temps rising into the low to mid 20s for highs. Over the Keweenaw, the ongoing LES band will begin weakening by midday as temps continue to warm and lake-based instability decreases. The snow there should be done by about sunset tomorrow evening. .LONG TERM...(Saturday night through Friday) Issued at 332 PM EST FRI JAN 22 2021 Models suggest a split flow developing across the CONUS through much of the extended with a progressive northern stream affecting the northern Great Lakes. After a brief period of slightly below normal temps this weekend, expect temperatures to slowly moderate through next week with above normal temperatures by the end of the week. Beginning late Sat night and Sun, models still in reasonable agreement that a northern stream shortwave and associated inverted sfc trough will bring an area of snow through the region from late Sat night into Sun. Forecast 280k-290k isentropic lift and 1.5-2 g/kg moisture available were consistent with the 0.10-0.20 inches of model QPF given the quick movement of the system. With SLR values likely in the 15/1 to 20/1 range, expect 1 to 3 inches of snow, highest south central and southeast. South to southeast winds and 850 mb temps around -11C may also bring the potential for some lake enhancement off of Lake Michigan into locations from MNM/ESC/ISQ where models suggest low level convergence will develop. This could maybe boost local snow accumulations in these areas close to 4 inches. Mon-Fri, increasingly confluent split flow and mean ridging into midweek will result in mostly dry conditions. Only exception will be some light LES in developing north-northeast flow for west and north central U.P. Mon-Wed. Strengthening southerly flow and WAA by late week, especially Fri, under mid-upper level ridging will continue dry conditions as 850 mb temps climb to 0 to -2C. Expect highs by Friday to reach near 30F across much of the area. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 709 PM EST FRI JAN 22 2021 VFR conditions are expected at IWD as light southwest flow and land breezes keep lake clouds off to the north. MVFR cigs at SAW should also give way to VFR overnight with most of the lake clouds remaining to the north. However, the clouds may remain close enough so that confidence in clearing is lower. CMX will be the challenging location. Models suggest that a moderate to heavy lake effect snow band will develop over western Lake Superior and move into the CMX area after about 02z. This band may initially lift to the north before moving back south and setting up to the south. Signficant variabitily in conditions will be possible with vsby at or below mins possible for a brief time. LES bands will likely persist into Saturday morning before gradually diminishing by Saturday afternoon. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 351 PM EST FRI JAN 22 2021 25 kt NW winds east half will subside below 20 kts tonight. A few pockets of 20-25 kt winds are possible across the lake on Sunday. Otherwise light winds 20 kts or less are expected across the lake through at least the middle of next week. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... Winter Weather Advisory until midnight EST tonight for MIZ006- 007-085. Winter Weather Advisory until 4 PM EST Saturday for MIZ001-003. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...RJC LONG TERM...Voss AVIATION...JLB MARINE...RJC
Area Forecast Discussion
National Weather Service Las Vegas NV
347 PM PST Fri Jan 22 2021 .SYNOPSIS...An active weather pattern will bring multiple low pressure systems across the region. The first will continue to impact our region this afternoon and evening with elevated southerly winds areawide and scattered showers and thunderstorms in southeastern Nevada and northwestern Arizona. A much colder system will arrive early next week bringing measurable snow to the mountains, rain for many of the valleys and the chance of low elevation snowfall. Late in the week, systems will take advantage of moisture from the atmospheric river, allowing the Sierra Nevada to accumulate significant snowfall. && .SHORT TERM...Today through Sunday. The first of several systems will continue to push through the area today before a reinforcing area of low pressure spins up and around the previous low, to bring lingering impacts. Wind Advisories remain in effect for western San Bernardino County up through Death Valley, eastward including western Clark County through 6pm PST tonight. Lake Wind Advisories for Lake Mead Recreation Area continue through 6pm as well as southerly wind gusts persist through sunset. Other than windy conditions, precipitation chances enter the forecast for much of Lincoln, Clark and Mohave counties this evening, with the best chances between 4pm and midnight PST tonight. Looking at forecast RAP and HRRR soundings for KLAS and KIGM (Las Vegas and Kingman), there exists a decent amount of CAPE as well as shear this evening. Though 250 J/kg of CAPE would be nothing to write home about in the Midwest or even during monsoon season, it is a decent amount to have in winter, particularly when coupled with upper level shear. Are we expecting severe thunderstorms tonight? No, but a rumble of thunder is not out of the question. For elevations below 6000 ft, the bulk of the precipitation expected tonight will be in the form of rain. However, above 6000 ft, snow is expected. Further, if a convective cell forms over higher elevation, convective snow has the capability of dropping a substantial amount of snow in a short period of time, with potential rain rates 2- 3"/hour. For this reason, confidence is moderate regarding snowfall totals tonight, as isolated higher amounts are possible underneath a stronger cell. All in all, this event will shape up to be relatively minor compared to next week`s systems. Widespread precipitation amounts between 0.10" and 0.30" expected tonight, though when the reinforcing area of low pressure swings around, so will additional chances of precipitation along southern Mohave County and southeastern San Bernardino County, that could amount to an additional 0.10" to 0.25" Saturday and Sunday. Otherwise, most areas can enjoy a break with dry weather on Sunday as we gear up for what the coming work week has in store. Winds will be overall calmer through the weekend than today, though elevated southerly winds can be expected. Temperatures will drop about 10 degrees between today`s highs and tomorrow`s highs, as the cold front pushes through the region tonight. Impacts are overall anticipated to be minor, but it is important to note that grime, oil and dirt build up on the roadways due to months without widespread wetting rains need very little rain to become incredibly slick. Double the distance between you and the car in front of you when driving, if you can, than you normally do. .LONG TERM...Monday through Thursday. The parade of weather continues. Monday morning, the next system will dip down the Western CONUS. Originating from Alaska, this system is substantially colder than its predecessors. As such, snow levels will drop to 3000 feet or lower, potentially reaching valley floors in some areas. As a result, measurable snowfall can be expected above 3500 ft, with a dusting to an inch possible even lower. Snow chances continue to remain elevated across the region on Monday, particularly, Monday morning. Looking at probabilistic NBM resources, valleys such as Las Vegas, Yucca Valley, and Bishop can expect to see snow in some capacity on Monday, with 40%, 72% and 78% respectively. ECMWF ensemble members are increasing in confidence as well regarding measurable snowfall here in Las Vegas, with only one member keeping all of the precipitation as rain. What does this mean for impacts? What about the roads? Though snow is possible, accumulating snow is not as likely, with Las Vegas sporting a whopping 1% chance of snow greater than 1 inch (though Yucca Valley and Bishop have better odds with 35% and 55% respectively). Additionally, ambient temperatures are not expected to drop low enough in Las Vegas to cool roadways and allow snow to accumulate. What could be a potential concern is black ice, depending on how much rain Las Vegas gets during the day on Monday, followed by how cold it gets Monday night/Tuesday morning. There is a nonzero chance of isolated spots of black ice around the valley if temperatures dip low enough for long enough. Chances of this at this time are low. The "Shift of Tails" from the Ensemble Situational Awareness Table, continues to indicate climatologically significant rainfall amounts across southern Nevada and northwestern Arizona Monday, further enhancing confidence. What is also shows, of note, is a climatologically significant amount of CAPE across the forecast area on Monday. This would indicate that there may be enough dynamics in place to overcome potentially meager moisture amounts... and would increase rain rates if there is a substantial amount of moisture left over from the weekend system. Regarding snowfall...confidence is not currently high enough to warrant any Winter Weather headlines at this time. Additionally, we want to avoid putting out any headlines this afternoon for Monday, as we don`t want people to confuse the headlines with tonight`s event. Snowfall rates will be highest Monday morning, decreasing through the event, with measurable amounts expected above 3500 ft. Due to low confidence in moisture potential, there is low confidence in precise snow totals at this time, but are trending upward for higher elevations and lower for the valleys. Wind does not look to be a major impact for most of the area for this system, but elevated southerly breezes can be expected. That said, areas with lower anticipated rain rates can expect stronger wind gusts. Areas that fit this description include cities south of I-40 including Barstow-Daggett and Lake Havasu City as well as potentially Yucca Valley and Twentynine Palms. Lake Wind products for Lake Havasu will be reevaluated as we get closer and have increased confidence, as these winds could result in waves 1.5-2.5 feet if they come to fruition. Additionally, local wind guidance as well as CONSMOS continue to trend upward for western San Bernardino County, so wind headlines may be necessary as we get closer and confidence increases. But wait, there`s more. The next system to drop down will coincide with a surge of moisture as a fairly robust atmospheric river funnels into the western CONUS. This system has the potential to dumb a substantial amount of snow on the Sierra Nevada and White Mountain ranges with chances of light rainfall elsewhere. && .AVIATION...For McCarran...Clouds continue to this afternoon as chances for rain increase into this evening. A few showers and isolated thunderstorms can be expected through the evening hours, ending by midnight. The greatest potential for showers and isolated thunderstorms impacting the terminal area will be between 01z-08z. Clouds as low as 4k-6k feet will be possible with heavier shower activity. Southerly winds will continue at around 15 kts gusting to 25 kts through 06z when wind will begin to slowly subside. For the rest of southern Nevada, northwest Arizona and southeast California...Windy conditions prevail over much of the area this evening as a weather system moves through the area. Southerly winds of 10-15 kts gusting to over 25 kts has been common, particularly along the Colorado River Valley. This will continue through the evening before winds begin to decrease after about 08z. Showers and isolated thunderstorms are possible this evening with the greatest chance between 01z and 08z. CIGs as low as 3-5kft are expected along the Colorado River and in areas through 08z and in areas with ongoing precipitation. Over southeast California, cloud bases will be higher, AOA 15kft except in areas of showers and precipitation will be more isolated. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && $$ DISCUSSION...Varian AVIATION...Berc For more forecast information...see us on our webpage: or follow us on Facebook and Twitter