Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/04/18

Area Forecast Discussion
National Weather Service Duluth MN
847 PM CST Sat Feb 3 2018 .UPDATE... Issued at 847 PM CST Sat Feb 3 2018 Most of the snow has ended across the Northland this evening. Snow showers will continue along portions of the South Shore due to northerly winds across Lake Superior. However, lowering inversion heights, drying, and increasing large scale subsidence should limit additional accumulation to an inch to possibly two inches tonight over localized areas. We will let the Winter Weather Advisory for Bayfield, Ashland, and Iron Counties expire at 03Z. Few other significant changes were made to the forecast tonight. UPDATE Issued at 538 PM CST Sat Feb 3 2018 We extended the Winter Weather Advisory for Bayfield, Ashland, and Iron Counties through 9 pm for additional accumulation of 1 to 3 inches due to lake processes. The snow over the rest of northern Wisconsin, inland from Lake Superior, should diminish between 6 pm and 8 pm and the Winter Weather Advisory there will end at 6 pm. && .SHORT TERM...(This evening through Sunday) Issued at 304 PM CST Sat Feb 3 2018 Light snow was falling across the Northland this afternoon in response to an area of low pressure centered over northern Iowa. The strongest forcing for ascent was found over central Wisconsin westward across east-central Minnesota, the Twin Cities, and then southwest to near Worthington, MN. Convective cloud tops were noted in the GOES-16 channel 2 imagery over those areas. RAP analysis indicated an area of 850-700 mb frontogenesis over our southern zones, which sloped farther south in the 900 mb to surface layer. The clouds were thinning across our northern zones with mostly sunny skies just across the International Border in northwest Ontario. The snow will taper off through this evening for all but northern Iron County and northern Bayfield County, where lake effect/ enhancement will support a prolonged period of light snow. Additional accumulation of an inch or two is anticipated, but could approach 4 inches in Gogebic Range of northern Iron County. Skies will clear from the north tonight as a surge of Arctic air pours into the Northland. By 04.12Z (Sunday morning), 925 mb temperatures will dip into the -25 to -30 C range across the Arrowhead and much of north-central and northeast Minnesota. Combined with clear skies and fresh snow, think temperatures will plummet overnight. The bias-corrected blends seemed to have the right idea, and have leaned on them for tonight. Have further lowered temperatures in the typically colder towns and localities with a few spots around -30 F for overnight lows. Since the strongest thermal advection will be focused aloft, we don`t anticipate much mixing, which would buoy temps overnight. Downslope drainage winds could develop tonight along the north shore from Silver Bay to Grand Portage resulting in northwest winds of 10 to 20 mph with stronger gusts. While the signal for drainage winds exists in the high-resolution guidance, the evening shift will have an opportunity to reassess the parameters and possibly raise wind speeds above the current values. With the cold temperatures tonight, even a light wind will create dangerous wind chills. Think the going headlines are in good shape and have not made any changes with this update. A ridge of high pressure will slide through the Northern Plains and into the middle Mississippi Valley Sunday with mainly sunny skies expected through the morning. As the ridge slides by to the south, winds will back westerly, bringing marginally warmer air into the Northland. Highs for Sunday seemed on track with the morning forecast, so few changes were made this afternoon. .LONG TERM...(Sunday night through Saturday) Issued at 304 PM CST Sat Feb 3 2018 The long term period will be dominated by below normal temperatures and a few opportunities for snow. High pressure will generally bring dry weather to the Northland from Sunday night into Wednesday. Overnight lows from Monday night through Tuesday night will generally range from the single digits below zero in the south, to the teens below zero in the north. Highs will range from 5 to 15 above from Monday through Wednesday. The models start to show some pretty big differences toward the end of the week, as they differ in their handling of a low pressure system that will be moving into the Central to Northern Plains. The ECMWF strengthens a surface low and brings it to eastern Nebraska by 00Z Friday, while the GFS has the surface low in the northern Rockies by that time. Widespread snow would be ongoing at that time according to the ECMWF, but it would be well west of the CWA on the GFS. By 12Z Friday, the ECMWF has the surface low over southern Lake Michigan, while the GFS has it near Sioux Falls with widespread snow across the entire CWA. The ECMWF would have the heaviest snow across the southern half of the CWA. At this point, we will go with a southern CWA solution, which would be closer to the ECMWF. Temperatures for the latter half of the week should continue well below normal, with single digits and teens for highs, and single digits and teens below zero for overnight lows. We will definitely have opportunities for wind chill headlines throughout much of this period, especially at night. The current 8 to 14 day outlook does show the potential for above normal temperatures during that time, so we should see a bit of a turn around after this next week. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 538 PM CST Sat Feb 3 2018 Surface low pressure, with a center in central Iowa, will continue to move east to northeast tonight with light snow ending from north to south. The snow has ended or has become considerably lighter over most of northeast Minnesota with light to moderate snow still falling from Pine County in Minnesota into northern Wisconsin. The snow in northern Wisconsin will be diminishing through the evening hours with potential lake effect snow continuing along the South Shore, mainly from portions of the Bayfield Peninsula east through Iron County. Drier air will arrive over Lake Superior overnight which should cause the lake effect to diminish. VFR conditions will expand across the Northland, but MVFR and possibly IFR ceilings will linger longer over portions of northern Wisconsin, especially along the South Shore. VFR conditions are expect for most areas Sunday. North to northeast winds this evening will back to west to southwest Sunday. && .PRELIMINARY POINT TEMPS/POPS... DLH -16 3 -8 11 / 20 0 0 0 INL -30 1 -12 5 / 0 10 10 0 BRD -15 4 -8 13 / 20 0 0 0 HYR -10 5 -10 15 / 100 10 0 0 ASX -6 6 -4 14 / 100 10 0 10 && .DLH WATCHES/WARNINGS/ADVISORIES... WI...Wind Chill Advisory from midnight tonight to noon CST Sunday for WIZ001. Winter Weather Advisory until 9 PM CST this evening for WIZ002>004. MN...Wind Chill Advisory from midnight tonight to noon CST Sunday for MNZ020-021-033>038. Wind Chill Advisory until noon CST Sunday for MNZ010>012-018-019- 025-026. LS...None. && $$ UPDATE...Melde SHORT TERM...Huyck LONG TERM...DAP AVIATION...Melde
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1005 PM EST Sat Feb 3 2018 .UPDATE... A pocket of low level dry air from the central Plains took the place of the afternoon light snow and brought a break in the pattern during early to mid evening. At the same time, a well defined entrance region of the upper level jet is moving from the upper Midwest to over Lake Superior during the evening. This is producing steady surface pressure falls over northern Lower Michigan and accelerating the low level jet ahead of the migrating surface low and front. The resulting 50 kt 850 mb flow in model data is a good representation of the intensifying moisture transport/theta-e advection to the point of near destabilization. This is shown by considerable texture in satellite imagery and in the character of radar suggesting strong vertical motion is occurring as the low level moisture axis is driven into Lower Michigan. Expect this initial band of snow moving along and north of the I-69 corridor will quickly saturate through to the surface before midnight as the low level theta-e ridge builds eastward and southward. Advisory worthy snow will then continue through the night leading into the event peak marked by the surface low reaching near Saginaw by sunrise. The timing still looks good for a burst of fgen along the arctic front as the surface low exits and the front makes a surge southward through the day. At this point, the incoming 00Z NAM is landing about in the middle on QPF/snow accumulation in the going headlines while the latest RAP definitely supports the upper end of the range in the Saginaw valley and northern Thumb. The current advisories look Ok for now with perhaps a slightly later onset south of I-69 which will be mentioned in the WSW update. For points farther south through the Detroit area, it has been a quiet and mild evening as dry air dominated and as temperatures surged into the lower and mid 30s. However, there is growing concern regarding the activity moving up from the lower Ohio valley that is part of a secondary moisture axis which is expected to merge with the prefrontal theta-e ridge ahead of the front. The RAP is also very bullish with QPF in the Detroit area during this process but observations so far are less than supportive. There is still a lot of high based clouds over Indiana among a lot of radar returns that indicate low level dry air is still a factor. Surface temperatures in the lower to mid 30s with a 20 degree dewpoint spread is also a negative factor for overachievement on accumulation. An advisory upgrade is not out of the question but plan to monitor evolution in this area to see if a headline might be warranted by the 4 AM forecast issuance. && .PREV DISCUSSION... Issued at 650 PM EST Sat Feb 3 2018 AVIATION... Surface low pressure developing from Iowa into northern Lower Michigan will enhance a dry southwest flow into the terminal corridor during the evening. The result will be a substantial break in snow over the region, especially south of FNT, while MBS remains on the edge of activity. VFR is expected to hold for several hours before snow reintensifies along and ahead of the associated frontal system toward midnight and beyond. A drop in conditions back down into IFR/LIFR will occur and continue through much of Sunday. This will be accompanied by relatively mild southwest surface wind around 10 kts and near surface low level wind shear until early Sunday morning. The LLWS will fade as the front approaches and moves through the region in exchange for the peak in snowfall intensity along the front followed by an abrupt wind shift to the north with gusts to 25 kts. The snow will exit during mid to late Sunday afternoon followed by a steady transition through MVFR and a partial clearing trend Sunday evening. For DTW... Virga will be common on radar during the evening but with only a passing flurry or light snow shower at the terminal. Ceiling will be mostly above 5000 ft during this time. A downward transition and renewed coverage and intensity of snow will develop overnight with peak intensity Sunday morning through early afternoon. Total snow accumulation of 3-4 inches is on target with some blowing and drifting as the wind shifts north and gusts near 25 knots by mid afternoon. /DTW THRESHOLD PROBABILITIES... * Low for ceiling 5000 ft or less through this evening, trending to high confidence by sunrise Sunday. * High for snow as precip type. * Low for ceiling 200 ft and/or visibility 1/2 sm. PREV DISCUSSION... Issued at 358 PM EST Sat Feb 3 2018 DISCUSSION... Deep isentropic ascent through nearly the entire column has saturated the resident dry layer with light snow falling across most or all of the area at press time. Nonetheless, dry air evident on the regional base reflectivity mosaic over far SE Wisconsin and northern Indiana will still have to work through the area over the next 4 to 6 hours. During this time, locations north of 8 Mile may receive around an inch while dry air has a greater impact to the south. DTX radar returns have intensified over central portions of the CWA over the last couple of hours. This is occurring in response to strong convergence at the lead edge of a rapidly intensifying LLJ. Intensity will continue to increase at it lifts north, leaving the northern fringes of the CWA to receive the highest snow totals through early evening, but the greatest forcing will ultimately set up over Lake Huron. Focus will then turn toward activity developing along the 850mb frontal zone which is currently in the early stages of fostering some disorganized higher intensity activity over eastern Iowa. As supporting PV filament lifts into the CWA, dry air will likely again plague much of the southern half of the CWA, while an fgen response along the impinging 850mb front supports a band of higher rates over a portion of the NW sector of the CWA. This is where the bulk of activity will be focused overnight. Cross-section analysis reveals rather high static stability, so the suppressed ageostrophic circulation will likely keep QPF/rates in check for the balance of the night. Yet another PV filament embedded in the flow well in advance of the primary wave will provide impetus for renewed snow development from the Detroit area south after 09z. Some intensity increase across the board likely 09-15z as increasing height falls sufficiently lower static stability to also allow for a more vigorous frontal circulation. By 12z Sunday morning, general expectations are for 2 to 4 inches north of I-69, tapering to 1 inch near 8 Mile, and under an inch to the south of there. Deformation along the frontal zone is expected to increase upon the approach of the primary mid-level wave during Sunday morning, leading to the peak rates of the event along a SW-NE axis roughly north of M-59 12-18z. Increased vertical motion amidst a gradually cooling thermal profile could support efficient snow ratios approaching 20:1 during this time, which lends support to a more aggressive forecast in the favored axis roughly along a Saginaw to Bad Axe line, shifting south toward an Owosso to Port Huron line during the morning. Flood of colder air and crashing dewpoints as the front is finally ushered east during the afternoon may briefly lead to improved ratios along the surface front itself, but will ultimately favor a reduction in intensity even as forcing increases as quality of ratios diminishes. Finally, potential for overachieving will exist in the eastern Thumb where developing northerly flow may produce lake enhancement prior to flow backing to NW after 21z. This potential will be worth monitoring as it would bring WSW criteria into play. Event total expectations are for a range of 2 to 5 over most of the area, lowest south of I-94, and 5 to 7 in the Thumb extending into at least a portion of the Saginaw Valley. Cold upstream airmass characterized by 850mb temps near -20C will filter into the area through Sunday aftn into the overnight, when low temps will fall into the single digits or slightly below zero. A modest gradient will bring wind chills to the brink of WC advisory criteria north of I-69. Low amplitude wave zipping around the periphery of the large scale trough anchored over the eastern half of the US will potentially bring a couple inches of snow to southern counties Monday night. Light overnight snowfall from shortwave impulse passing over southern MI will come to an end early Tuesday. High pressure will build over the area for the rest of the day and result in quiet and calm weather. High temps will remain on the cool side, reaching the mid to upper 20s. Quiet and cool weather looks to stick around for Wednesday. The ECMWF still wants our area to receive some snowfall from a developing eastern CONUS low pressure system, but its latest run has trended a bit eastward with the snow and has therefore started to approach the solution the GFS and Canadian models have been advertising for days (no snow for SE Michigan). Will continue to monitor as the energy behind this system moves onshore, however, not expecting significant impacts at this time. The eastern CONUS system will help amplify the thermal trough over our area and bring a shot of Arctic air back in. The GFS has been hinting at some snow showers on Thursday as the base of the longwave trough passes over, but yet to see this signal emerge in the Euro or Canadian models. Conditions otherwise on Thursday will remain seasonably cool. A digging shortwave will lead to a developing cyclone over the northern plains which will move into the Great Lakes on Friday into Saturday, bringing a better chance for precipitation. High pressure will follow in its wake for the remainder of next weekend. MARINE... A brisk 15 to 25 knot south to southwest wind will persist into tonight in advance of low pressure and an arctic front. Gust potential remains limited, ensuring gusts remain below gales during this time. Winds turn northerly and become strong as the front drops across the lakes on Sunday. Brief gusts to low end gales are possible over central sections of Lake Huron during this time. This system will result in a period of widespread accumulating snow lasting through late Sunday. Winds will then shift to the west on Monday as high pressure slides across the Ohio Valley. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...Winter Weather Advisory until 7 PM EST Sunday for MIZ047>049- 053>055-060. Winter Weather Advisory until 7 PM EST Sunday for MIZ061>063- 068>070. Lake Huron...NONE. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ UPDATE.......BT AVIATION.....BT DISCUSSION...JVC/TF MARINE.......MR You can obtain your latest National Weather Service forecasts online at
Area Forecast Discussion
National Weather Service Grand Rapids MI
950 PM EST Sat Feb 3 2018 LATEST UPDATE... Update .SYNOPSIS... Issued at 300 PM EST Sat Feb 3 2018 Periods of snow will continue across the area into Sunday afternoon before diminishing. Most areas will see total accumulations of 3 to 6 inches, with some higher amounts north of Muskegon. A brief break in the weather is expected Sunday night and much of Monday with only some light lake effect expected along the lakeshore. Another system will then begin to affect the area late Monday and Monday night with some additional accumulations likely. Additional chances for snow will exist through the remainder of the week, with generally below average temperatures expected. && .UPDATE... Issued at 951 PM EST Sat Feb 3 2018 Our forecast and headlines are on track so I plan to keep a steady course and allow this all to play out. The evening we are being aided by mid level FGEN and Sunday morning we have the deformation band on the north side of the system as the cold air comes in. Most of the snow from this system will fall between now and sunrise. The heaviest being over our NW CWA (which is what we have been forecasting). That area has the best FGEN tonight and is in the deformation zone longest. Plus there is a touch of lake effect to help the cause Sunday afternoon. I could see 8 to 12 inches in some sections of Mason County. Our snow accumulations algorithm is already showing 6 to 8 inches over northern Muskegon County. Our radar overshoots the core of the echoes north of that. In any event the 8 to 12 inches for a storm total makes sense given what our radar shows and what we expect yet to fall. The latest run of the HRRR and HRRRX are slower to move the deformation band out of the CWA, compared to the NAMNEST. If that were in fact what actually did happen that would mean snow may fall into the early afternoon over eastern sections. As the cold air comes in winds will be gusty so I added blowing snow to the forecast Sunday morning. && .SHORT TERM...(This evening through Monday night) Issued at 300 PM EST Sat Feb 3 2018 No changes are going to be made with the headlines with this forecast package. The only things that might need to be adjusted with time would be an upgrade to a warning across the NW if snow falls to heavily, or some slight adjustments with regards to expiration times depending on the timing of the impactful snow out of the area on Sun. We are still thinking a general 3-6 inch event for much of the area, with locally higher amounts across the NW of up to 10 inches through Sunday. The duration of the snow across the NW will keep those accumulations from being too high of an impact. The heaviest snow will be across the NW portion of the area through tonight and will diminish Sun morning as the front sinks far enough SE and offshore flow takes shape. The heaviest snow for the SE portion of the area will come overnight tonight and through Sunday morning. This comes as the sfc front will sink into that portion of the area, and the upper wave passage takes place. There is fairly good consensus amongst the models, so we feel good at this time with the advisory. Some lake effect will be possible along the immediate lakeshore counties late Sun and Sun night with NNW flow and colder air coming back in. This lake effect should not be of much consequence as the ridging coming in the wake of the Sun upper wave will drive inversion heights down to around 3-4k feet AGL. We will not have to wait long then for our next synoptic snow event in this active pattern taking shape over the nrn CONUS. We will see a jet streak dive SE out of Canada and ride along the U.S./Canadian border. There is not much of a sfc low with this system, but there is quite a bit of stronger mid-level fgen that develops and moves through as a result of the RRQ of the strong jet streak. This will focus much of the snow late Mon and mainly Mon night across the South. The lakeshore may see some slightly elevated amounts with lake enhancement occurring with a wrly low level flow. Right now it looks like up to about 4 inches will be possible (highest South). The details still are a bit uncertain, especially with it being a fgen event and where bands may set up. .LONG TERM...(Tuesday through Saturday) Issued at 300 PM EST Sat Feb 3 2018 Active weather pattern continues through next week. There is still some lingering uncertainty on the potential for snow on Wednesday morning as the low tracks well to the southeast of Lower Michigan. As for the latest trend in the models...the 12Z Euro is consistent with previous runs and remains more amplified with the pattern and stronger with the sfc low which it tracks through the Ohio Valley, close enough to bring the northern edge of the snow into Lower Michigan. Meanwhile, the GFS is also consistent in showing less amplitude and a flat wave moving off the mid-Atlantic coast with the northern edge of its precip missing us to the south. The model blend forecast reflects this solution and was not changed as the GFS has been correct in a couple past events that looked similar to this one in previous weeks. An arctic front moving through Wednesday night should bring a burst of snow followed by some lake effect snow shower Wednesday night. A more significant northern stream low is depicted by both the Euro and GFS for late Thursday or Friday tracking across Lower Michigan. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 623 PM EST Sat Feb 3 2018 The break in the snow activity is about to come to an end as the upper level wave gets closer to the area. All TAF sites should become IFR by 03z or so. I expect occasional LIFR between 09z and 18z Sunday as the frontal system moves through. MKG, GRR and possibly AZO will have the lowest conditions. Also once the cold front comes through just between 10z and 14z (west to east) winds will become gusty causing some blowing and drifting snow too. The snow will likely not come to an end till late in the day at most of the TAF sites. && .HYDROLOGY... Issued at 300 PM EST Sat Feb 3 2018 At approximately 10:40 a.m., an impressive mass of broken ice was observed making its way down the Grand River, past Robinson Twp. Large chunks of ice continued passing by the River Haven Marina for about 20 minutes, before coming to a stop just after 11 a.m. Coordination with Emergency Management revealed that the ice flow was impeded by the river bend north of the 144th Ave and Green St intersection. River levels rose slightly near Robinson Twp and even more so at Eastmanville. No flooding resulted and no additional rises have been noted, indicating that water continues to pass under the ice jammed ice. Should water continue to easily flow underneath the ice and ice remains in place, it is fair to assume that there is no immediate threat. However, it will continue to be monitored. Other sites have experienced little change. Colder weather has resulted in erratic behavior on some river gauges, as usual. The advisory remains in effect for the Looking Glass River at Eagle with continued fluctuation noted again this morning. As advertised, additional precipitation will be in the form of snow through the weekend and into next week. No near term impacts are expected. Any flooding concerns will be related to potential ice jams with the Grand River at Robinson Twp serving as this morning`s best example. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Winter Weather Advisory until 9 AM EST Sunday for MIZ037>040- 043>046-050>052-056-057-064. Winter Weather Advisory until 5 PM EST Sunday for MIZ058-059- 065>067-071>074. LM...None. && $$ UPDATE...WDM SYNOPSIS...NJJ SHORT TERM...NJJ LONG TERM...JAM AVIATION...WDM HYDROLOGY...JAM
National Weather Service Jackson KY
737 PM EST Sat Feb 3 2018 .UPDATE... Issued at 735 PM EST SAT FEB 3 2018 Hourly temperature and dewpoint grids have been updated based on recent observations and trends. It still looks like a mix of rain and snow or snow initially with wetbulbing and perhaps lift leading to a slight cooling of the column for a couple of hours of snow for many locations. Air temperatures and ground temperatures should be marginal for many locations at the freezing mark if not a degree or two above. There is also some chance for sleet to mix in initially with the dry low level dewpoints which are in the teens across the board if not a tad drier in the 2.5 to 4kft msl layer over the far southeast per Flatwoods/Dorton area and Black Mtn summit KY Mesonet station observations and perhaps during the transition back to rain. The previous start time and onset times appear to be in good shape. Some of the eastern valley locations have dropped off to just above the freezing mark and with that in mind other than the warmer southwest locations, snowfall in the grids was increased slightly for southeast valleys to about two tenths or so. With marginal temperatures expected through the event accumulations should be greatest on grassy and elevated surface. && .SHORT TERM...(This evening through Sunday night) Issued at 325 PM EST SAT FEB 3 2018 19z sfc analysis shows high pressure on the retreat through eastern Kentucky. This high has been ineffectual in keeping the mid level clouds from covering the area and starting to thicken/lower. Even so, winds switching to the south and picking up at 5 to 10 mph are helping to support a much milder afternoon than yesterday with readings generally in the upper 30s to lower 40s and still climbing. Dewpoints, meanwhile, remain fairly dry in the mid to upper teens most places. It is these lower dewpoints and the wetbulb principle that will make for a messy forecast later tonight as a slug of pcpn moves in well ahead of a cold front. The models are in good agreement aloft with the longwave pattern through the short term, though the GEM lags the others late in the period. They all do depict a flat pattern amplifying tonight as mid level energy and a trough dig into the Midwest. The lead energy with this spreads over Kentucky after midnight into Sunday morning accompanied by the right rear entrance region of a developing jet streak at 300 mb. All told this will enhance the lift over the area via upper level divergence into 12z Sunday. A Stronger short wave will lead the main trough into the Ohio Valley Sunday night into Monday morning bringing larger height falls to the area, though the deeper moisture will have shifted off to the east earlier on Sunday. Given the general model symmetry and consensus of the higher resolution ones in the near term have followed a blend with emphasis on the HRRR and NAM12 for details. Sensible weather will feature cloudy and mild conditions late this afternoon through the evening. At this point all indications are that the temperatures will stay above freezing through dawn - even in the eastern valleys given the thickening clouds and warm advection pattern. In fact, some of the warmest low level temperatures should seep into the southeast part of the state earliest calling into question the snow potential over the higher terrain. However, with the dry air in place and tough to dislodge the wetbulb effect will likely lower readings once the measurable pcpn hits, that should prolong the snow and changeover from late tonight into dawn Sunday most places. Before the warm air wins out late tonight, expect some small accumulations of snow, generally a half inch or less - though up to an inch possible in the spots where the heavier pcpn occurs. Warming conditions still into the evening and temperatures remaining above freezing tonight should keep the roads warm enough to melt the snow on contact similar to what happened, on Thursday. This will need to be monitored closely this evening and into the overnight, though, as the pcpn is certainly coming and lingering cold pockets could be extra messy at least for a time. For this reason, along with the expectation of some sleet (partially melted snowflakes) during the transition to rain across the CWA, will continue and beef up the ongoing SPS for this wintry weather event tonight into Sunday morning. Rain then follows through Sunday before a dry slot cuts off the pcpn and moves to the east while the cold front associated with the mid level trough`s core will spread in around or shortly after 00z Monday. This will yield another shot of light snow across the area along with a period of upslope flow in its wake. At this point, just a half an inch or less accumulation is expected from this system`s exit as temperatures bottom out in the upper teens and lower 20s by Monday morning. Again used the CONSShort and ShortBlend as the starting point for all the grids with some complicated temperature adjustments between 06 and 15z to account for the wetbulbing in the face of low level warm advection. As for PoPs, slowed them down to be closer to the HRRR timing this evening and early in the overnight - also enhanced them Sunday night. .LONG TERM...(Monday through Saturday) Issued at 325 PM EST SAT FEB 3 2018 An upper level trough will be on it`s way out of the area, as an area of high pressure builds eastward on Monday. Did keep some lingering snow showers and/or flurries early Monday before the moisture drys up. This surface high will aid in bringing a period of dry weather Monday afternoon into Monday night. Then we watch the next system take shape across the Southern Plains and before this we see a weak disturbance pass through the Ohio Valley. This weak system will have more minimal impacts, with eyes remaining on the southern stream system That said, an area of low pressure will deepen and track across the Southern Mississippi River Valley Late Tuesday. The models are struggling coming into alignment with the low track, with the GFS being the more in between bringing this low pressure right along the spin of the Appalachians and many of the GEFS perturbations indicating a similar low track as well. This would lead to a small window of mix of rain/snow in the Bluegrass Tuesday morning before going all rain through early Wednesday. Then probably switching back rain and/or snow through the day on Wednesday into Wednesday night. Given the uncertainty will stick with this scenario for now and see if more model agreement develops in the future. The 06Z run of the GFS did have a deformation zone develop across the region leading to a period of moderate to even heavy rainfall Tuesday night under ample lifting, but the latest GFS backed off some in the latest run. Overall the period from Tuesday into early Wednesday would yield around an inch to an inch and quarter of QPE This progressive pattern will bring another area of high pressure and dry period across eastern Kentucky Thursday into Friday. The temperatures finally warm back into the lower 50s by Friday. Then another storm system develops and progresses into the area to round out the period. However, the models are struggling even more to come to a consensus at this point in the forecast process. Therefore, limited the POPs to chance given the timing and separate streams of energy possibly in play. The type of precipitation could be a mix of rain/snow Friday night before going back to rain Saturday, but the uncertainty with this is great at this point given the model differences. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) ISSUED AT 725 PM EST SAT FEB 3 2018 VFR conditions will continue to prevail until the 7 to 12Z period as the lower levels gradually saturate and cloud bases and at times vis lower to MVFR range as precipitation arrives ahead of a cold front. This will likely initially be a mix of rain and snow possibly mixed with sleet. A couple hour period of snow should follow before precipitation switches to all rain as the entire column warms above freezing ahead of the cold front 8Z to 14Z. As low levels saturate some fog will also be possible at the TAF sites with IFR likely developing 11Z to 17Z along and behind the cold front, which should linger through the end of the period. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JP SHORT TERM...GREIF LONG TERM...DJ AVIATION...JP
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
611 PM CST Sat Feb 3 2018 .SHORT TERM...(This evening through Sunday) Issued at 145 PM CST Sat Feb 3 2018 Couple of areas of snow with the heavier accumulation moving through eastern cwa now. Expect rapid improvement in as this moves east through about 00z. However, another band of snow associated with another wave/frontogenesis will drop southeast over the area through the overnight providing the continuation of at least light snow/flurries through at 06z across the southern areas. Total accumulation of 2-4 inches looks good mainly along an north of I94 through early evening. May see an additional half inch as so with that secondary band this evening. We will allow the winter weather advisory expire at 6 PM. Clearing s the arctic air arrives later tonight Sunday morning with timing of the wind chill advisory remains as is for now. Similar temperatures and winds from the overnight still gave us 20 to 30 below with a few 35 below values near KAXN late. Temperatures will struggle to warm through the single digits, especially over areas seeing the heavier/fresher snow cover. .LONG TERM...(Sunday night through Saturday) Issued at 145 PM CST Sat Feb 3 2018 Longer term concerns remain the couple of chances for accumulating snow - namely Monday across the south and across most of the area Thursday/Friday time period. The monday system could clip far southern MN with a couple inches of snow Monday. This trend continues. Some timing issues for the Thursday/Friday system this far out but that system does appear to be as strong/if not a bit stronger than the system moving through now. GEFS probability plots should high probability of greater that 4 inches in 24 hours across the central cwa/similar to todays system. Upper level flow pattern/jet stream continue to favor northwest flow across the area. This will maintain the below normal temperatures through the end of the period. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 611 PM CST Sat Feb 3 2018 Bulk of snow has ended, but there`s one last upper wave over central MN that has to drop through here. Forcing with this wave is much weaker and additional snowfall is going to be light, with basically a prolonged period of 2sm-4sm snow expected, per HRRR and GFSlamp forecasts. Cigs are a bit trickier this evening as they have mostly improved to VFR, though as colder air works in overnight, we could see them drop before skies go skc in the morning. KMSP...The 22z run of the hrrr has backed off on additional snow, but decent band to the north on radar will swing through here, which will provide us with another round of mainly MVFR vis snow. Only concern is that it may come through a bit faster than current TAF portrays. /OUTLOOK FOR KMSP/ Mon...VFR. Wind SW 5-10 kts. Tue...Chc MVFR CIGS. Wind WNW 5 kts. Wed...Chc MVFR CIGS. Wind SW 5 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... WI...Winter Weather Advisory until 6 PM CST this evening for WIZ014>016-025-027. MN...Wind Chill Advisory from 4 AM to noon CST Sunday for MNZ044-045- 049>053-057>063-065>070-073>076-082-083-091. Wind Chill Advisory from midnight tonight to noon CST Sunday for MNZ041>043-047-048-054>056-064. Winter Weather Advisory until 6 PM CST this evening for MNZ045- 052-053. && $$ SHORT TERM...DWE LONG TERM...DWE AVIATION...MPG
Area Forecast Discussion
National Weather Service Paducah KY
644 PM CST Sat Feb 3 2018 .UPDATE... Issued at 644 PM CST Sat Feb 3 2018 Only minor modifications made to the going forecast. Airmass still trying to saturate as the low levels remain very dry. One band of returns was from south central MO into southwest IL. HRRR seems to be handling well another area of development from northeast AR into far west TN. The precip should move and expand northeast through 10 p.m. into west KY and the MO Bootheel region. Overall, still expect rather light QPF amounts across the north and northwest part of the CWFA, best QPF west KY. Light snow will likely mix with light rain at onset and may fall as mostly snow across the Evansville Tri State (10 p.m. to 1 a.m.) for an hour or two until diabatic processes are overcome. Minimal, mostly trace accumulations on grassy surfaces expected. Otherwise mainly light rains. Temps were on track and dew points are starting to rise. && .SHORT TERM...(Tonight through Monday) Issued at 200 PM CST Sat Feb 3 2018 Warm advection cloudiness prevails this pm, but most of the column transition is in the mid-upper levels as surface dew points remain in the teens. This should change during the next 12 hours, with dew points into the lower 30s by 12Z Sunday. Early night lows in the 30s may actually bump up a little by tmrw morning as the warm front lifts north, so we`ll likely try to trend that non diurnal curve overnight if it doesn`t look too bad collaboratively. As for pcpn chances, note low layer southerlies through the entirety of the event. Analysis of sounding data suggests only a 3 hour window for ice crystals, falling into still dry sub 850 mb layer, and by the time it saturates, best crystal formation potential is beginning to wane. Liked the Builder`s pickup on this with less than 1 inch totals everywhere and generally less than 1/2 inch totals for most, confining all totals to the north. Reinforcing cold shot comes tmrw night, with Lows in the teens, underneath a 1030 mb Arctic surface High. Then its slide eastward leads to some return flow warm advection setting up Monday with moderating temps/dew points to follow. .LONG TERM...(Monday night through Saturday) Issued at 200 PM CST Sat Feb 3 2018 Low level warm air and moisture advection will lead to a chance of precip beginning Monday evening across the north part of the FA in response to a weak 500 mb short wave. Otherwise, the models are in fairly good agreement in delaying the bulk of the precip across the FA until Tuesday afternoon when large scale lift will be ongoing as surface low pressure approaches the ARKLATEX region. The chance for the greatest QPF will be across SEMO, far W KY, and adjacent portions of S IL. By Wednesday morning the precip, in the form of snow/rain mix, should be limited to mainly W KY and end before noon as surface high pressure builds in from the NW behind the departing cold front to our SE. As far as the type of precip, atmospheric profiles indicate the event may start out as a wintry mix mainly over the southern parts of SEMO late Monday night, then expanding northeastward and trending toward all liquid Tuesday morning as temps slowly climb through the 30s north into the 40s south. Some minimal ice/snow accumulations are possible over about the SW half of the FA through Tuesday morning. As the colder air begins to arrive later in the day, a NW to SE transition back to snow or a wintry mix is expected. There is potential for 1 to 2 plus inches of snow roughly north of the Ohio River to northern parts of SEMO as the colder air arrival coincides with adequate moisture Tuesday evening. Some minor accumulations are possible overnight Tuesday night into Wednesday morning elsewhere across the FA. Surface high pressure will then dominate through mid week with temps somewhat below normal. Temps will then moderate before another cold front brings a chance of precip through the early part of next weekend. && .AVIATION... Issued at 552 PM CST Sat Feb 3 2018 Mid level ceilings between 7-10kft agl will start the 00z Sunday WFO PAH TAF issuance, but rapidly drop to lower VFR category/high end MVFR ceilings between 04-06z, as nocturnal cooling of the layer, combined with precipitation loading from above, combine to saturate the atmosphere. The WFO PAH TAF sites will remain north of an inverted trough/developing frontal boundary over the lower Mississippi Valley this evening and overnight. A mean visibility of five (5) statute miles is forecast given the mixing in the boundary layer, but would not be surprised to see visibilities dropping down to three (3) statute miles at times overnight. A frontal boundary and gradual wind shift moves in between 10z and 16z across the WFO PAH TAF sites. Visibilities are improved to VFR Category, but cold air post-frontal stratocumulus will keep ceilings in the upper MVFR category (2.5-3kft AGL) for the rest of the forecast period with NW winds 10-15 knots, gusting 17-22 knots at times. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...None. MO...None. IN...None. KY...None. && $$ AVIATION...Smith