Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/23/18

Area Forecast Discussion
National Weather Service State College PA
722 PM EST Mon Jan 22 2018 .SYNOPSIS... A potent area of low pressure moving across the Great Lakes will push a trailing cold front through the Commonwealth on Tuesday. Temperatures will stay above normal into early Tuesday, before falling back to near or slightly below normal Wednesday and Thursday. Dry weather is expected for the second half of the week. The temperatures will rebound to above normals by the weekend. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... Regional radar mosaic at 23Z shows light precip associated with WAA and 850mb baroclinic zone lifting north of the state, while band of showers associated with approaching cold front remain to the west. Latest HRRR and earlier HREFV2 indicate showers will overspread the Allegheny Plateau between 02Z-04Z, then reach the Susq Valley by 06Z-07Z. A marginally unstable air mass, combined with strong forcing along cold front, could produce some briefly heavy downpours and thunder late tonight. Based on latest operational model output, and earlier ensembles, will maintain POPS of near 100 pct tonight. 23Z surface analysis shows quasi-stationary front remains hung up along the spine of the Appalachians with little movement anticipated overnight. Based on this, and low dewpoint depressions, will go with nearly steady temperatures overnight. Have added mention of patchy fog across the northeast portion of the forecast area this evening based on current observations. However, arrival of rain and an increasing breeze should scour out the fog in the valley locations late tonight. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... Model consensus pushes the cold(occluded) front through the eastern half of the forecast area between 12Z-15Z. Will maintain a near 100 pct chance of showers and possible thunder in this area early in the day, then rapidly lower POPS as drier air works in behind the front. Breaking clouds expected by afternoon over the eastern half of the forecast area, as surface ridging builds into the region. However, upslope flow is likely to cause stratocu to linger over the Alleghenies and passage of upper low across the eastern Grt Lks is likely to spread snow showers into the northwest mountains late in the day. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... Cold front and low pressure system will be lifting into New England by Tue night, with secondary front bringing colder air back into PA - along with snow showers in western sections that will taper off by Wed night (after only amounting to an inch or two). Breezy winds up to 30 mph will also impact central PA during that time as temperatures fall back to seasonal levels. Thu and Fri will be cooler as high pressure moves across the region. Eastern areas especially will see chilly mornings as dry air/low dewpoints associated with the high will be in place. Progressive pattern will bring moderating temperatures back for the weekend ahead of another low pressure area. Chances for rain increase heading into Sunday, followed by a return of cooler weather and snow showers behind a cold front Monday. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... Wind speed will increase aloft as a strong low level jet noses in and intensifies over PA. SSW wind at 2-3kft will peak around 55KT late tonight. A cold front will push through around sunrise in the W, and early aftn in the E. There will be occasional SHRA through the night, and the wind will be generally light through the night. IFR will likely be limited to inside the showers. There is a very small chance of TS in the area overnight, and in the SE Tues before 18Z. Have not mentioned it in the TAF yet due to low confidence of occurrence. Expect the LLWS to not go away until CFROPA, then mechanical mixing will make it very gusty on Tues. The highest gusts will be at JST. Cold air will turn the lingering SHRA over the W in the aftn to SHSN. SCT SHSN will then continue over the high terrain of the west into Wed. Outlook... Wed...AM shsn possible w mtns. Thu-Sat...No sig wx expected. && .HYDROLOGY... After coordination with local officials, some concern does still exist for minor flooding along and near the Susq between York Haven and Safe Harbor. Therefore, the Flood Watch for this area has been extended into Tuesday afternoon. Due to the mild temperatures, there is a potential for ice movement, but there will also be deterioration/thinning of the ice through time. All locations along rivers and streams that have significant ice buildup should monitor water levels closely. The anticipated rainfall totals of 0.5 to 1.0 inches over the next 48 hrs is much less than we had a few days ago, and the ice is less pervasive/extensive due to our relatively mild temps (versus the period leading up to our previous significant rainfall). So, no other areas will be placed into Flood Watch at this time. && .CTP WATCHES/WARNINGS/ADVISORIES... Flood Watch through Tuesday afternoon for PAZ065-066. && $$ SYNOPSIS...Dangelo NEAR TERM...Fitzgerald SHORT TERM...Dangelo/Fitzgerald LONG TERM...Lambert/RXR AVIATION...Dangelo/Tyburski HYDROLOGY...Ross
Area Forecast Discussion
National Weather Service Duluth MN
824 PM CST Mon Jan 22 2018 .UPDATE... Issued at 821 PM CST Mon Jan 22 2018 Heavy snow continued through the evening commute, but radar trends over the last hour indicate the precipitation was definitely diminishing across northwest Wisconsin. As expected, snowfall amounts across the advisory/warning area were highly variable. In general, we should see an inch or less in the western areas, and another 1 to 3 at most in the east. The 23Z HRRR seemed to have a good handle on the current trends. Will likely continue the headlines through the current advisory/warning end time. && .SHORT TERM...(This evening through Tuesday) Issued at 332 PM CST Mon Jan 22 2018 The forecast remains on track regarding the winter storm moving through the Northland this afternoon and tonight. As of 3 PM this afternoon, surface low pressure was centered over southern Iowa with a closed 500 mb circulation over northern Missouri. This storm system will move eastward across southern Wisconsin and into southern Lower Michigan by late tonight. A broad band of snow stretched from eastern Nebraska and northeast Kansas north into southwest Minnesota and then east across the Twin Cities Metro and into central and northwest Wisconsin. Snow rates of 1 to 2 inches per hour have been reported over portions of southern and east- central Minnesota this afternoon. A strong frontogenetically forced band of snow stretched from the Twin Cities to near Phillips, WI and was rotating northward. A period of heavy snow is expected as this band lifts northwestward across Sawyer and Price Counties and southern portions of Washburn, Bayfield, Ashland and Iron Counties. The frontogenetic snow band is expected to pivot and then pull east-northeastward with two periods of heavy snow possible. Periods of near-whiteout conditions are possible, especially on ridgetops and hill crests. Widespread visibility of one-half to one-quarter mile are expected where conditions are less windy. Additional accumulation over the afore mentioned areas of 2 to 6 inches are expected through 6 PM, with another 1 to 4 inches by midnight. To the north and west of the snow, a mix of light snow and freezing drizzle continues. Sensible heat and moisture flux from Lake Superior continues to support shallow convection and convergence, resulting in bands of snow. Outside of those convective and convergent bands, precipitation rates are lower and the column profiles indicate freezing drizzle. Look for the freezing drizzle potential to diminish this evening as the column cools, changing over to all light snow before ending. Snowfall totals and placement are largely unchanged from this morning with a swath of 8-12 inches across southeast Sawyer and all of Price County, and lower totals farther northwest. No changes to headlines with the afternoon update as the advisory and warning areas seem well placed. .LONG TERM...(Tuesday night through Monday) Issued at 332 PM CST Mon Jan 22 2018 The Northland is looking at relatively quiet weather for much of the rest of the week. Weak surface high pressure will move through the region during the middle of the week, and an upper-level ridge will build into Northland by late Thursday. This upper-level ridge will bring a plume of warmer air into region, resulting in a period of milder weather. The Northland could get a relatively warm day late this week depending on the timing of when this wave of warm air moves through the Northland. It currently looks like the timing of when the axis of warmest air will likely pass through the Northland Thursday evening or early Friday, rather than during the day Thursday or Friday. If it would pass through during the daytime, then the warmer air combined with a little sunshine could really mean a warm day in the 40s. The GFS`s timing is about 6 to 12 hours faster than the European and Canadian model runs, but all three have the axis timing through the Northland Thursday night or early Friday. A Canadian Clipper will be on the heels of this plume of warmer air. This Clipper will likely pass near or just north of the Canadian border Friday and Friday night, and it will bring light and snow through the Northland Friday and Friday night. Lingering snow flurries and cold, blustery winds are possible Saturday and Saturday night. This latest wind forecast does not reflect these blustery, gusty winds because of timing differences between the models generating a blend of overall weaker winds. The GFS is much faster bringing in the cold air into the Northland than the Canadian and European. We will likely increase the wind forecast once we better determine when that surge of Arctic air comes into the Northland, with widespread gust potential of 20 to 30 mph. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 533 PM CST Mon Jan 22 2018 Widespread MVFR conditions are expected across the Northland overnight and into early Tuesday. Snow will continue across northwest Wisconsin this evening, with MVFR to IFR CIG`s and VSBY`s at KHYR through the evening. The remainder of the region will see MVFR CIG`s, but some improvement is expected as the night wears on, as drier air is pulled in from the northeast. The result will be VFR to MVFR conditions during the latter part of the night, which will give way to largely VFR conditions on Tuesday morning. && .PRELIMINARY POINT TEMPS/POPS... DLH 10 23 10 24 / 10 0 10 10 INL -2 17 4 24 / 0 10 10 10 BRD 14 25 13 27 / 10 10 10 0 HYR 18 27 7 26 / 100 10 0 0 ASX 20 24 9 25 / 90 50 10 10 && .DLH WATCHES/WARNINGS/ADVISORIES... WI...Winter Storm Warning until midnight CST tonight for WIZ003-004- 008-009. Winter Weather Advisory until midnight CST tonight for WIZ001- 002-006-007. MN...None. LS...None. && $$ UPDATE...DAP SHORT TERM...Huyck LONG TERM...Grochocinski AVIATION...DAP
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1017 PM EST Mon Jan 22 2018 .SYNOPSIS... A moist cold front will move across the forecast area later tonight and tomorrow morning. In the fronts wake, dry high pressure will overspread the region and persist into the weekend. Another moist cold front will affect the region over the weekend. && .NEAR TERM /THROUGH TUESDAY/... As of 1000 PM: Water-vapor imagery shows a partially occluded cyclone centered over Illinois. The cold front associated with this system extends south thru the lower Ohio Valley, middle TN, and AL, as evidenced by slight wind shift and dewpoint gradient. Over our CWFA, a fairly contiguous area of showers is being forced by upper divergence and DPVA, with additional enhancement due to brisk southerly low-level flow. Updated overnight PoPs using latest CAM output as a guide. In particular the HRRR continues to advect the current activity to the NE. With continued moist flow, dewpoints keep rising overnight over the Piedmont, and this leads to development of SBCAPE in the early morning hours, per NAM and RAP. As we have been messaging for several days, this is concerning given the robust LLJ and associated low-level shear parameters. SPC suddenly placed focus on our area with a Marginal Risk on the evening Day 1 outlook update. It certainly can`t be ruled out that a few isolated Broken-S type structures could develop along the sfc cold front when it arrives. That said, over the past few cycles the CAMs have been depicting only disorganized activity with the front. Also the HRRR has nearly zero SBCAPE. Winds within the LLJ may produce some problems above 3500 ft. Day shift extended the advisory to 11z in collaboration with neighbors; that product will be updated shortly. Temps will be elevated overnight under clouds and strong LLVL WAA; revised values are based on short-term consensus product and reflect steady temps in the east, and onset of CAA in the west. On Tuesday, there will be a brief window of strong gusts right behind the fropa, as 925 mb veer to SWLY and remain in the 35-40 kt range with CAA. This looks to be around daybreak, then winds should subside a bit and continue to veer to NWLY by late morning. Some sort of Wind Advisory may be needed in the mountains and possibly in the piedmont early Tuesday, if guidance trends stronger with the llvl winds. For now, will let the later shifts assess the threat and make a decision. By the aftn, skies will clear out, except right along the TN border, with NW flow bringing some wrap-around moisture. A slight CHC PoP for ra/sn showers returns by the end of the day. Temps will be noticeably cooler in the high terrain with the CAA, while the Piedmont should remain above normal with help of downslope warming. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/... As of 135 PM EST Monday: A weak short wave crosses the area Tuesday night as the upper low moves NE across New England. A stronger short wave moves into the area Wednesday then east of the area Wednesday night. Heights rise Thursday as a ridge axis moves east toward the area. At the surface, a moist northwesterly upslope flow remains over the mountains Tuesday night. The pressure gradient slowly relaxes as the cold front moves east of the area and high pressure to the west slowly moves east. This keeps clouds and scattered to isolated snow showers along the TN border with clearing skies elsewhere. The clouds will linger across the mountains and perhaps some isolated snow showers along the TN border of the northern mountains Wednesday as the second short wave moves through. Do not expect any significant accumulation with these snow showers, but cannot rule out up to an inch across the highest elevations of the northern mountains. May even see some of the clouds break containment and spread across the foothills and piedmont during the day. Windy to breezy conditions will continue across the mountains with breezy conditions developing on Wednesday elsewhere. Lows Tuesday night and highs Wednesday will be near to slightly above normal. Winds, clouds and any lingering isolated snow showers diminish Wednesday night with sunny skies expected Thursday as high pressure builds in from the west. Lows Wednesday night drop a little below normal while highs Thursday remain nearly steady near or a little above normal. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... As of 225 PM Monday...the extended fcst begins at 00z on Friday with a fairly progressive upper-lvl pattern expected thru the period. By early Friday, heights will be rising over the fcst area as a broad upper trof moves off the Atlantic Coast and steep upper ridging moves over the Eastern CONUS. The ridge will be short lived and is expected to translate offshore early Sat as another upper trof moves across the Great Lakes later on Sat and into Sun. The trof axis will likely move north of the fcst area by late Sun and then possibly amplify again on Monday to end the period. At the sfc, expansive high pressure will be in place over the region to start the period. By late Fri/early Sat, the high will be drifting offshore putting the CWFA back under warmer, SLY low-lvl flow. At the same time, a cold front will be approaching the fcst area from the west. The latest model guidance suggests that the fropa will occur on Sunday with the ECMWF being the slower solution. By roughly 12z Monday, things should be drying out as high pressure spreads back over the area. && .AVIATION /03Z TUESDAY THROUGH SATURDAY/... At KCLT and elsewhere: Mainly low VFR to MVFR cigs begin the period. An upper disturbance will swing over the terminals this evening, bringing a period of rainfall. The rain is expected to bring temporary vsby restrictions and should usher in IFR cigs. IFR is expected to linger until a cold front sweeps through in the morning, leaving mostly clear skies. Strong flow is already present above the PBL and it is possible some of the overnight showers will bring down gusts above 20 kt. Occasional rumbles of thunder are not out of the question but appear too isolated to mention in TAFs. Once the front clears, veering winds look likely to bring more frequent gusts, likely being stronger than what occurs overnight. Outlook: Dry high pressure will dominate the area through the remainder of the week. Another system will move in over the weekend, bringing another round of -SHRA and restrictions. Confidence Table... 03-09Z 09-15Z 15-21Z 21-00Z KCLT Med 66% Med 78% High 86% High 100% KGSP Low 59% Med 76% High 100% High 100% KAVL High 88% High 83% High 100% High 100% KHKY Med 71% High 81% High 100% High 100% KGMU Med 62% High 85% High 100% High 100% KAND Med 76% High 80% High 100% High 100% The percentage reflects the number of guidance members agreeing with the scheduled TAF issuance flight rule category. Complete hourly experimental aviation forecast consistency tables and ensemble forecasts are available at the following link: && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...Wind Advisory until 6 AM EST Tuesday for NCZ033-048>053-058- 059. SC...None. && $$ SYNOPSIS...JPT NEAR TERM...ARK/Wimberley SHORT TERM...RWH LONG TERM...JPT AVIATION...Wimberley
Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
804 PM CST Mon Jan 22 2018 .UPDATE... Updated for evening discussion. && .DISCUSSION... Evening update discussion: The previous forecast for tonight is basically on track. Surface pressures continue to slowly increase in the wake of the cold front that came through earlier today with all precipitation well clear of the area. Surface winds will have a tough time decoupling through the night on the bottom fringes of winter storm affecting the Midwest and these winds will prevent optimum radiational cooling from occurring in most areas. Also, there is a band of higher cirrus running from southwest to northeast over the Pine Belt currently and this band will have a tendency to "back up" further toward the heart of the region through tomorrow morning, generally preventing totally clear skies in many areas through the entire night. Not sure these clouds will be thick enough to further hurt radiational cooling potential, but they will not help it out either. Anticipate lows by morning to mainly range from the upper 30s to lower 40s, although some spotty mid 30s cannot be ruled out in typically colder spots that consistently manage to radiate most affectively. /BB/ Prior discussion below: Tonight through Tuesday: Latest rap and satellite analysis showed the upper trough moving into the Mississippi Valley from the Plains. The cold front was tracking across our eastern counties with the rain east of the forecast area. Readings across the region were in the 60s. For the period expect quiet conditions as the upper trough axis exits to the east as we get into a zonal flow pattern on Tuesday. Surface high pressure will build in from the Southern Plains. As far as temperatures are concerned in the wake of the front under clear skies we will dip back down into the 30s for tonight with highs in the 50s on Tuesday./17/ Tuesday night through Sunday: Zonal mid level flow pattern through much of the week will give way to ridging from the west by Thursday. This should keep temperatures relatively cool through a good portion of the week with a gradual warming trend ensuing by late week. Meanwhile, another storm system will begin strengthening over the Intermountain West. The models differ from this point forward. While the GFS/Canadian have backed off on the strength of this system as it pulls into the Plains Friday, the ECMWF still maintains better amplification and thus better forcing as its attendant cold front moves into the area Saturday. At the moment will lean toward the more consistent amplified ECMWF. Despite the differences in the models, a strong signal still exists in all model solutions in that a large convective area will develop along the LA/MS Gulf Coast. This continues to manifest itself further north in our forecast area with run to run lessening with overall QPF. This is understandable in the less amplified GFS/Canadian, but the better forced ECMWF is also showing this. Will have to watch this trend in later cycles and possibly back off on POPs/QPF if the trend continues./26/ && .AVIATION... 00Z TAF discussion: Expect VFR conditions through the period with only a few high and thin cirrus clouds (based above 20 kft) streaming across the region between now and tomorrow. Surface winds are currently from the west to southwest at 5 to 10 kts and will remain this way through the night. Tomorrow, expect winds to transition more to the northwest and be near 10 kts with occasional gusts up to 20 kts not out of the question. /BB/ && .PRELIMINARY POINT TEMPS/POPS... Jackson 39 58 33 56 / 0 0 2 2 Meridian 39 58 31 57 / 0 0 2 2 Vicksburg 37 59 32 56 / 0 0 2 2 Hattiesburg 40 62 35 58 / 0 0 2 1 Natchez 38 61 32 56 / 0 0 2 2 Greenville 37 56 32 53 / 0 0 2 1 Greenwood 37 54 30 53 / 0 0 2 2 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...None. LA...None. AR...None. && $$ 17/26/BB
Area Forecast Discussion
National Weather Service Louisville KY
903 PM EST Mon Jan 22 2018 .Forecast Update... Issued at 900 PM EST Mon Jan 22 2018 Most of the cells across the region are not bringing down stronger winds, with just a few showing pea-sized hail and one that got tall enough for a warning. The back edge of the precip is where the strongest winds have been so far this evening, with gusts around 50 mph at FTK, SDF, and LOU in the last hour. There must be just enough of a mix down occurring along that back edge to allow some of the stronger winds aloft to get down to the surface. Otherwise, the automated gauges and Kentucky Mesonet sites are not showing stronger winds at this time. Will have to continue watching storms along this back edge for any rotations, as that would bring a better chance to get it to the surface. Issued at 655 PM EST Mon Jan 22 2018 Line of showers and a few thunderstorms embedded forming a little farther west than the HRRR anticipated. The NAMNest, which has been doing a great job in the near term the last several weeks, has picked up on the location better, and thus have leaned toward this model in the near term, as well as current observations from radar. Environment appears supportive for some low-topped supercells, and have seen a couple form along our western forecast area, near Lewisport, KY and Tell City, IN. Have seen some good rotation with these storm, and will continue to monitor trends. Otherwise, seeing wind gusts of 30-40 mph out there, and we may see a few storms with stronger gusts the rest of this evening. && .Short Term...(This evening through Tuesday night) Issued at 301 PM EST Mon Jan 22 2018 ...Gusty Showers Expected This Evening... GOES East imagery shows an impressive and mature cyclone over the upper Midwest. Today`s widespread rainfall associated with the warm conveyor portion of the cyclone has continued to weaken as it pushes east, however still expect everyone to get some rain so likely to categorical pops continue east of I-65 for another couple of hours. The focus then shifts back to the west as an impressive dry slot begins to work into western KY. Hi-res models have been pegging redevelopment of showers (and perhaps an isolated T) somewhere along or W of I-65 late this afternoon and early this evening. This would occur as the approaching cold front (still back over the mid Mississippi River Valley) combines with exit region dynamics to kick of sct-numerous showers. Given that the low level jet will still be around 45-50 knots, worried that the steepening lapse rates will help some stronger gusts get down to the surface with the showers. At this point, thinking some Special Weather Statement worthy gusts of 40+ mph are possible. Still not all that confident on exactly if the showers will redevelop to the magnitude that the HRRR shows, but if they do am more confident that we will see some pretty healthy gusts. Think this would be better handled by short fused SPS`s than any Wind Advisory product given the expected convective and short- lived nature. Still, synoptic winds outside of any showers could still gust up to 35 mph through the overnight. Later tonight, low level moisture associated with the comma head of the mature cyclone moves into our CWA, with deep enough moisture to squeeze out some measurable light showers and sprinkles, mainly across our northern CWA. Temps fall off into the upper 30s and low 40s through Tuesday morning, but think thermal profile stays warm enough for rain. As we move deeper into the day on Tuesday, will continue to keep low chances for a measurable shower and/or sprinkles. Also think we could see a few ice pellets mix in given some positive area (steep low level lapse rates) extending well above the freezing level. Low level moisture still looks to linger into Tuesday night where temp profiles begin to be cold enough to possibly support some flurries. Lows should drop into the mid and upper 20s. .Long Term...(Wednesday through Monday) Issued at 301 PM EST Mon Jan 22 2018 Wednesday - Friday... A secondary shortwave will slide through on Wednesday. Low level moisture should remain trapped through this time, so added ascent from the passing shortwave could be enough to kick off some continued flurries or sprinkles. Will keep a dry forecast (from a measurable standpoint) but may have to mention chances for a sprinkle or flurry through Wednesday night. Highs should struggle into the low 40s. Dry NW flow aloft and surface high pressure will then dominate through Thursday night, keeping us dry with steadily moderating temperatures. Highs by Thursday will be in the upper 40s to low 50s. After Wednesday night lows in the mid 20s, Thursday night lows should trend milder to around freezing. Progressive upper ridge axis slides through on Friday, and will bring another dry and warmer day. Look for highs in the mid 50s. Friday Night - Saturday Night... Models have trended less amplified and faster with the weekend system, which will bring shower chances in by Friday night. The bulk of the rainfall should be on Saturday as deeper moisture pools ahead of the upper trough axis, along the surface cold front. Given the faster and less amplified trend, it`s going to be harder for any cold air to catch up to lingering moisture on the back side of the system. So, think a mostly rain forecast is still the way to go. After a milder Friday night in the mid 40s, Saturday highs will also be in the mid 50s, with temps falling off Saturday night behind the front. Sunday - Monday... Dry NW flow and surface high pressure then control for the remainder of this forecast cycle. Slightly cooler temps take hold with lows just below freezing and highs in the 40s. && .Aviation...(00Z TAF Issuance) Issued at 620 PM EST Mon Jan 22 2018 Have some pretty gusty winds out there now, as a potent low pressure system drags a cold front across the region. Also seeing a few showers pop up with some isolated thunder. This rain will not last long, but we could see some gusts to 35 knots either with or without the rain. A clear slot will come behind these showers before we should get socked in with lower clouds by daybreak Tuesday. For now time-height sections indicate these should stay MVFR, but that they should persist through the rest of the day. Wind gusts will persist through the period as well. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Update...RJS Short Term...BJS Long Term...BJS Aviation...RJS
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
924 PM CST Mon Jan 22 2018 .UPDATE... 924 PM CST The main forecast concern for later tonight is the potential for a band of snow to develop across portions of far northern IL into early Tuesday morning. Water vapor imagery early this evening indicates that the main mid-level circulation is now beginning to shift northeastward into far west-central IL (just north of Quincey, IL). The surface low over eastern Iowa has become occluded over the past several hours, with a new center of low pressure now developing over far northeastern IL and southeast WI this evening. Given the occlusion of the main storm system, a well defined TROWAL (TRough Of Warm Air Aloft) structure has developed to the north of the main circulation into southern WI. Ultimately this is setting up prime conditions for the development of a rather intense area of mid- level frontogenesis along the southern periphery of this TROWAL where mid-level deformation is strengthening in association with the arrival of the mid-level low. Radar trends across far northern Illinois and far southern Wisconsin already indicate that this process is underway as a nearly stationary band of precipitation resides. The main concern is that as dynamic adiabatic cooling continues and colder air begins to wrap back into northern IL tonight that this will result in the change over to a band of potentially heavy snow into early Tuesday morning. Overall confidence on the trends of this change over to snow remains low at this time, but guidance indicates that the column should become sufficiently cold to support a change over to snow around midnight over northern IL. Given the presence of steep mid-level lapse rates above the TROWAL, heavy snow will be possible across far northern IL later tonight. The main question that remains is how much snow will fall. There certainly is the potential to get a quick few inches of wet snow near the WI state line, but amounts would likely rapidly drop off to the south towards the I-88 corridor. I tossed around the idea of putting an advisory up for my far northern counties, but have opted to hold off for now and go with a special weather statement. Given the potential impacts to the morning rush, an advisory could be needed later tonight. Given the above, I have increased snow amounts far north to around 2-3 inches, with a change over to snow expected around, or shortly after midnight. KJB && .SHORT TERM... 200 PM CST Through Tuesday... Low pressure is centered near Des Moines, Iowa this afternoon with a warm front draped across far northern Illinois. In the vicinity of the front, fog and drizzle will continue this afternoon across far northern Illinois while farther south dry air wrapping in from the southwest has allowed partial clearing west of the I-57 corridor. Temperatures and dew points are into the upper 40s to low 50s within the warm sector and are superimposed by steep low to mid level lapse rates this afternoon which are contributing to a corridor of seasonably strong instability. Midday soundings from DVN and ILX show MLCAPE values around 150 J/kg while SBCAPE is closer to 600 J/kg. Latest run of the RAP picks up on this axis of instability and shifts it east across the CWA through the late afternoon and early evening ahead of an advancing cold front, albeit with weakening instability as we get past peak heating. Very strong winds aloft with 0-1km shear in excess of 20kt and favorable effective SRH continue to prompt some concern for a severe threat for any thunderstorms that make it into the area this afternoon and evening, and an isolated tornado remains a possibility. Convective initiation is already ongoing near Springfield, IL with agitated cu field south towards St Louis. These storms will move north-northeast through the late afternoon and evening hours within the aforementioned instability axis though confidence in how well they will maintain their intensity is fairly low by the time they reach the local CWA. Late this evening and overnight, 500mb closed low will move across the region and allow deeper moisture to return resulting in periods of light rain. Forecast soundings eventually cool enough for precipitation to transition to snow during the predawn and early morning hours Tuesday. Models have been fairly consistent showing axis of highest QPF near and north of the IL/WI state line. As precipitation changes to snow, could see a dusting/few tenths of snow area-wide, but the best chance for any light accumulations will be across the northern tier of counties where up to an inch of snow is possible. Winds turn northwest behind the departing low Tuesday morning and mid level moisture scours out once more. Steep low level lapse rates redevelop in the northwest flow and could result in a few additional flurries during the late morning and afternoon. Temps will fall into the low to mid 30s behind the cold front tonight and likely hold fairly steady through the day tomorrow. Deubelbeiss && .LONG TERM... 140 PM CST Tuesday night through Monday... Closed upper low continues to pull away from the region Tuesday evening, with mid-level short wave ridging building briefly across the area early in the night. Partial clearing of lower clouds is possible during the evening in response to mid-level drying and subsidence associated with strong H5 height falls (nearly 150 meters), though forecast soundings depict redevelopment of mid- level clouds overnight as another mid-level short wave quickly approaches. Clouds linger through the day Wednesday as the wave propagates across the region, with a weak surface cold frontal trough. Model soundings depict a relatively dry 900-700 mb layer however, which suggests little precip threat despite cloudy skies. Model 950 mb temps generally support daytime highs in the low-mid 30`s. Mid-level short wave and larger scale upper trough axis moves east of the area Wednesday night. Medium range guidance is in good agreement in building broad upper ridging east across the region, with dry and milder conditions Thursday and Friday. Pattern is progressive, with an upper trough developing eastward across the central and northern Plains, and an area of surface low pressure which tracks into western Ontario and trails a cold front through the local area Friday night or early Saturday. Surface high initially blocking gulf moisture return, and relatively quick progression of upper flow, suggests somewhat limited precipitation potential, especially with quicker cold frontal passage depicted by the GFS. Slower ECMWF/GEM solutions would support a little greater potential for rain especially across the southeastern part of the cwa into Saturday. After 40`s Thursday, and temps likely near 50 Friday, timing differences with the cold front add lower confidence to the high temp forecast Saturday, with 45-50 degree highs likely east/southeast of the advancing front. Colder air spreads back in behind the front Saturday night, though by the time precipitation ends in the southeast, model partial thickness values would suggest precip type would likely remain all rain. By Monday, even the slowest guidance (ECMWF) moves the upper trough east of the area, with broad upper ridging moving in aloft with weak high pressure ridge at the surface. Some detail differences exist as expected by that time, though generally it appears our colder air will result in temps around average for late January. Pattern looks to remain progressive as well, with milder air again early-mid next week. Ratzer && .AVIATION... For the 00Z TAFs... Several forecast concerns/challenges this forecast period: * Showers and Thunder this evening * A band of light/moderate, possibly heavy, snow tonight thru Tue AM * Returning IFR ceilings, with LIFR possible * Wind shift to the northwest Tue AM * Continued scattered snow showers Tue Latest radar imagery showing area of showers and thunderstorms continuing to move across much of northern Illinois. RFD currently being impacted but expect the remaining terminals to see this precip over the next hour, with thunder still a possibility. However, ORD/DPA have the highest chances of observing this thunder along with a possibility of small hail. Showers will then linger for 2-3 hours but should diminish in coverage after that point, while conditions remain mainly VFR. The arrival of colder air and stronger forcing later tonight will support a window of light to moderate snow, and have adjusted TAFs to account for latest trends. This will start earlier at RFD, but then spread east southeast soon there after. Have higher confidence of snow now occurring, but do think there could be a window of heavier snow. Have lowest vis falling to 1sm, but vis below 1sm is possible. Will need to monitor this period and potential snow, especially as snow accumulation will be possible at the terminals. Ceilings will fall under this snow, with IFR a definite possibility. LIFR will also be possible. Conditions should improve by early Tuesday morning, but with winds shifting to the northwest and with periodic snow showers continuing throughout the day. Rodriguez && .MARINE... 155 PM CST Main marine forecast concerns focus on deep area of low pressure which will move across southern Lake Michigan tonight. In addition, areas of locally dense fog were in place across southern parts of the lake, where 40-50 degree dew point air has spread north over the colder waters. Strong northeast winds currently occurring across northern parts of the lake will gradually back northerly and increase more solidly into gale range through early Tuesday morning as the low moves through, and will increase to gale strength over the southern portion of the lake Tuesday morning as the low pulls off to the east. Gale warning headlines are already up for the north half, though there winds are largely just below gale force this afternoon. A gale warning is in effect for the southern part of the lake starting early Tuesday morning, and headlines for the entire lake will run through 00Z/6 pm CST tomorrow. A dense fog advisory remains in effect into this evening on the south end of the lake. The low will eventually move off across the St. Lawrence Valley Tuesday night, with weak high pressure ridging spreading across the western Lakes Wednesday. This will allow winds to diminish to less than 20 kts, and eventually back to the south-southwest by early Thursday. Deep low pressure is expected to develop in the lee of the Northern Rockies Thursday night, which will induce increasing south-southeast winds. A period of southerly gales is possible Friday through perhaps early Saturday, after which a cold front will shift winds to the west. Ratzer && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...Dense Fog Advisory...LMZ777-LMZ779 until 3 AM Tuesday. Gale Warning...LMZ777-LMZ779...3 AM Tuesday to 6 PM Tuesday. Small Craft Advisory...LMZ740-LMZ741-LMZ742...6 AM Tuesday to 4 AM Wednesday. Small Craft Advisory...LMZ743-LMZ744-LMZ745...6 AM Tuesday to 10 AM Wednesday. && $$ VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE) FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSCHICAGO WWW.TWITTER.COM/NWSCHICAGO WWW.YOUTUBE.COM/NWSCHICAGO
Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
910 PM CST Mon Jan 22 2018 .DISCUSSION...See updated information for land and marine areas below. && .UPDATE...Have updated to remove slight chance pops over the easternmost portion of the area with dry conditions expected for the remainder of the night. Made other minor adjustments. /29 && .MARINE...Have extended the Marine Dense Fog Advisory for the Mobile Bay area and the adjacent near shore waters until 05Z. A cold front currently advancing across southeast Mississippi will move through later this evening and scour out the fog where the advisory is in effect. /29 && .PREV DISCUSSION... /issued 601 PM CST Mon Jan 22 2018/ DISCUSSION...Updated for latest aviation discussion below. AVIATION... 00Z issuance...Mostly MVFR cigs and visibilities through about 23.04z followed by VFR conditions through 24.00z. A short period of low stratus and fog will also be possible through 24.04z ahead of a cold front approaching from the northwest. Winds will be south to southwest at 8 to 12 knots through about 23.04z shifting northwest late this evening through 24.00z. 32/ee PREV DISCUSSION... /issued 535 PM CST Mon Jan 22 2018/ DISCUSSION...See updated information for land areas below. UPDATE...Have updated to lower pops to slight chance over the eastern third of the area based on current radar trends and the latest high resolution guidance. No other major changes. /29 PREV DISCUSSION... /issued 400 PM CST Mon Jan 22 2018/ NEAR TERM /Now Through Tuesday/...Surface analysis indicates that the surface cold front is making its way into east central MS and southeast LA. Winds are veering southwesterly to westerly with dewpoints falling into the 30s and 40s behind the boundary. The front is entering our far northwestern zones as of 3 PM, with clouds beginning to decrease over Wayne and Choctaw counties. Overcast skies and moist southerly flow otherwise persists over much of our area ahead of the front. Radar indicates convection has become scattered in nature over much of the region, except for a zone of better coverage near the northwest FL Panhandle coast. Ascent associated with the shortwave trough axis will become focused over the eastern CWA ahead of the approaching front through the rest of this afternoon, and this is where the best chance of convection will be through 00z. POPs will meanwhile quickly decrease over western and northern areas as the front moves across this portion of the region through late afternoon. We still cannot rule out an isolated strong storm or two over the eastern CWA through the rest of the afternoon where residual weak MLCAPE values mostly below 400 J/KG will persist, but the overall lack of instability will preclude an organized severe threat. There could be some patchy fog develop near the immediate coast late this afternoon into early this evening prior to the passage of the front. Otherwise, winds will gradually turn west to northwest following frontal passage late this evening into the overnight hours with a cooler and drier airmass arriving in the wake of this feature. Sunny skies and dry conditions are expected Tuesday underneath dry zonal flow aloft. /21 SHORT TERM /Tuesday night Through Thursday night/...Upper level zonal flow along with building high pressure will keep conditions dry and cool through Thursday. Although this airmass will not be anywhere near as cold as the past few systems. Clear skies can be expected with temperatures near seasonable levels. /13 LONG TERM /Friday Through Monday/...An upper trough will develop across the plains and move east late in the week. As this system approaches, moisture levels will increase across the area as southerly flow develops. This will bring increasing rain chances from the west on Friday. Rain becomes widespread Saturday and Saturday night as an area of low pressure develops and moves east ahead of the trough. The GFS and ECMWF differ on how strong the low will and where it tracks as they handle the upper shortwave differently. The Euro is much more amplified which allows the low to move across the area Saturday night into Sunday morning. Meanwhile, GFS has a weaker shortwave and keeps the low track across the Gulf. We have left thunder out of the forecast for now, but will be something to watch to see how it develops late in the period. /13 MARINE...Moist southerly flow over the cool nearshore waters will maintain potential for areas of dense marine fog over Mobile Bay, the Mississippi Sound, Perdido Bay, and the adjacent offshore waters out 20 NM through early this evening. The NAM, RAP, and HRRR all show continued potential for areas of fog over these areas, with relatively high probabilities for fog also indicated on the SREF. Will keep the Dense Fog Advisory in effect for these areas until 9 PM. A drier airmass then arrives with increasing northwest winds this evening following the passage of a cold front. Winds will be at advisory levels offshore, so will have a Small Craft Advisory in effect for the Gulf waters out 60 NM from midnight tonight through 9 AM Tuesday. A moderate to occasionally strong offshore flow will continue Wednesday and Thursday, before becoming more easterly Friday and into the weekend. /21 && .MOB WATCHES/WARNINGS/ADVISORIES... AL...None. FL...None. MS...None. GM...Dense Fog Advisory until 11 PM CST this evening for GMZ630>633- 650. Small Craft Advisory until 9 AM CST Tuesday for GMZ650-655-670- 675. && $$ This product is also available on the web at:
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
554 PM CST Mon Jan 22 2018 .SHORT TERM...(This evening through Tuesday) Issued at 310 PM CST Mon Jan 22 2018 Water vapor imagery showing upper low drifting slowly e-ne across northeast MO this afternoon. Enhanced area of clouds now over southeast MN and is beginning to pivot. Another area of enhanced clouds drifting into far southern MN where moderate to heavy snow has been falling much of the afternoon. Strong north/northeast winds gusting to 35-40 kts at times continue into south central area, where they have already observed 8 to 12 in the heavy snow band. Significant blowing and drifting snow with near whiteout conditions expected to continue through the remainder of the afternoon in the blizzard warning area. The greater rates have worked into the southern Metro where 1 to 2 inches an hour will likely continue through about 6-7 PM. Will likely see around a foot of snow in Scott and Dakota Co. with 6 to 10 inches likely across the metro. The system is forecast to exit to the east this evening and will continue the headlines through 06Z. An addition 1 to 3 inches likely accumulating after 6 PM over the southeast area. Trimmed the highs for Tuesday over the expected heavy snow area over south central MN into western WI. Otherwise, we should see more sunshine for Tuesday. .LONG TERM...(Tuesday night through Monday) Issued at 310 PM CST Mon Jan 22 2018 The weather pattern will be progressive for the extended period, however no significant hazardous weather is expected. The shortwave that is anticipated to pass through overnight Tuesday into Wednesday morning will keep skies mostly cloudy through Thursday. Temperatures will become more mild as the week continues as the thermal ridge builds-in on Thursday and continues through Friday. Temperatures will be above-normal with highs reaching the lower to mid 40s on Friday. This third January thaw will not last long as a cold front will arrive late Friday into Saturday morning. Depending on the exact timing of the front, Saturday may be one of those days where the high temperatures of mid to upper 30s occur close to midnight in the Eastern half of our CWA. There is a chance for light snowfall late Saturday into Sunday, primarily over West Central Wisconsin, with an upper-level trough in place. Temperatures will remain near normal to slightly below normal on Sunday and Monday. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 554 PM CST Mon Jan 22 2018 Deformation band continues to go strong across the Twin Cities metro and looking at the HRRR, this band is not going anywhere for the next 3-5 hours, so delayed improvements toward a hrrr timing for MSP/MKT/RNH/EAU. After the snow, HRRR and other hi-res models show a clearing aggressively working south out of northern MN in the subsidence behind this system. However, the stratus behind this system goes clear up to the middle of Lake Winnipeg, so went with the slower timing for cig improvements seen with the GFS Bufkit profiles and LAV guidance. Monday afternoon we will see another shortwave coming at us from the Dakotas. LAV shows some MVFR cigs trying to work back in out west during the afternoon, but that doesn`t have much support from GFS soundings. Instead it looks like an increase in mid level clouds. KMSP...Based on continued high reflectivity in the band just west of MSP and HRRR forecasts showing this deformation band lingering through at least 5z, delayed improvements to above 1/2sm in snow until 4z. This may be a little long, but will watch trends. Another 2-4 inches of snow is expected before the snow finally ends. /OUTLOOK FOR KMSP/ Wed...MVFR/IFR cigs. Winds SW 5 kts. Thu...Chc MVFR/IFR cigs. Winds SE 5-10 kts. Fri...Mainly VFR. Winds S-SW 5-15 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... WI...Winter Storm Warning until midnight CST tonight for WIZ014>016- 023>028. MN...Winter Storm Warning until midnight CST tonight for MNZ060>063- 067>070-078. Winter Weather Advisory until midnight CST tonight for MNZ053- 065-066-073. Blizzard Warning until midnight CST tonight for MNZ074>077- 082>085-091>093. && $$ SHORT TERM...DWE LONG TERM...AMK AVIATION...MPG
Area Forecast Discussion
National Weather Service Tallahassee FL
821 PM EST Mon Jan 22 2018 .UPDATE... Trimmed PoPs across our western areas as HRRR and other Hi-Res models shifting the highest chances east and current radar reflects this. Little instability has led to lightning strikes mainly over the waters and virtually NIL across land areas so have pulled thunder from the land areas. Highest chances overnight will be across the eastern third of the CWA plus the coastal waters. Cold front upstream will make it across most of the CWA by dawn. Ahead of the front, low clouds and possible fog is possible until the front passes by. && .PREV DISCUSSION [614 PM EST]... .NEAR TERM [Through Tonight]... At 1 pm EST a surface cold front extended southward through eastern MS, southeast LA, and into the western Gulf of Mexico from a 995 mb low centered over IA. The mid-upper tropospheric low was positioned near the surface low, indicating that the low was near maturity. Ragged bands of showers and thunderstorms preceded this surface front, and will be moving east across our forecast area later this afternoon through tonight. While 0-6km bulk shear values suggest storm organization is possible, poor thermodynamics will make it difficult to sustain strong updrafts, or for surface-based damaging wind gusts. So far recent upstream radar imagery and surface observations bear this out, as there haven`t been any significant wind gusts where there was organized reflectivity. For most of our forecast area temperatures will be well above average, with lows in the mid 50s to low 60s. However, lows in the upper 40s are expected in southeast AL and the western FL Panhandle, where the cold front will have moved through before daybreak. Ahead of the front, areas of fog will be possible, mainly between the time when the rain ends and the cold front arrives. .SHORT TERM [Tuesday Through Wednesday Night]... The cold front will continue sweeping eastward across the remainder of the forecast area Tuesday, with a cooler, drier airmass moving in behind it. Temperatures will warm to the 60s Tuesday, but will struggle to hit 60 Wednesday as the cold air advection continues. Overnight, temperatures will dip into the mid-upper 30s Tuesday night, low-mid 30s on Wednesday night. .LONG TERM [Thursday Through Monday]... A shortwave upper level trough will lift northeastward from central Mexico toward the central Gulf coast, helping develop a disturbance in the western Gulf waters that will move toward the north-central Gulf coastline. As this system will spend its early life cycle over the Gulf waters, it`s expected to be very rich in moisture and bring a decent amount of rain with it. Early estimates from WPC are around 1-2" accumulations this weekend, with higher rainfall totals offshore and to our west. The storm will move eastward out of the area by Sunday night, with a dry start to the following work week. .AVIATION [Through 00Z Wednesday]... Degraded flt conds for the next 12-15 hours with showers across the area and cigs decreasing to LIFR overnight. A cold front is located to our west and vsbys will also decrease overnight. Conds will persist until the cold front moves through at which time flt conds will return to VFR. .MARINE... Winds and seas will be agitated by tonight`s frontal passage and will remain elevated for the next several days as a low pressure system develops in the western Gulf and then moves into our forecast area this weekend. Cautionary conditions are expected the next few days, with advisory conditions possibly developing around Wednesday night for our offshore waters. .FIRE WEATHER... A few areas could briefly reach locally critical RH values Tuesday afternoon. However, tonight`s rain and weakening winds on Tuesday should prevent Red Flag conditions are not expected. .HYDROLOGY... Rainfall totals from the approaching cold front will be around 0.5- 1", which is not expected to cause any flooding concerns. This weekend, we`ll have another chance for rain, this time with higher rainfall totals expected, around 1-2", which should be welcomed given our current drought. .SPOTTER INFORMATION STATEMENT... Spotter activation is not requested. However, spotters are always encouraged to safely report significant weather conditions when they occur by calling the office or tweeting us @NWSTallahassee. && .PRELIMINARY POINT TEMPS/POPS... Tallahassee 56 68 38 59 34 / 80 10 0 0 0 Panama City 54 63 41 57 39 / 80 0 0 0 0 Dothan 48 64 36 59 33 / 50 0 0 0 0 Albany 52 65 37 60 34 / 70 0 0 0 0 Valdosta 59 66 39 57 36 / 80 20 0 0 0 Cross City 61 70 39 60 35 / 80 40 0 0 0 Apalachicola 57 65 41 57 38 / 80 0 0 0 0 && .TAE WATCHES/WARNINGS/ADVISORIES... FL...None. GA...None. AL...None. GM...None. && $$ UPDATE...Scholl NEAR TERM...Fournier SHORT TERM...Nguyen LONG TERM...Nguyen AVIATION...Scholl MARINE...Nguyen FIRE WEATHER...Fournier HYDROLOGY...Nguyen
...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Tuesday) Issued at 301 PM CST Mon Jan 22 2018 Surface low pressure continues to exit northeast Kansas moving northeast towards the Great Lakes region. Gusty northwest winds have been seen through the afternoon with gusts around 40mph observed as a tight pressure gradient is observed over the area. Light to moderate snow/rain has been falling across north central Kansas this afternoon making its way east as it rotates counter- clockwise around the low pressure. The greatest snowfall totals still look to be in north central Kansas and near the Kansas/Nebraska border, with amounts just over two inches expected with locally higher amounts. Advisory has been expanded a few more hours in time and farther eastward, to capture additional snowfall amounts in windy conditions that will likely have some impact on school and work commutes. Still expect hazardous road conditions and lower visibilities as this snow falls due to the high wind speeds between 20-25 mph sustained through midnight. As precipitation moves northeast out of the area, a changeover to all snow will be seen as temperatures fall below freezing. Expect all snow to come to an end after midnight tonight. There could still be some slick spots on any untreated, wet roads so cautious travel is advised. Winds decrease overnight as the low departs and lows will fall into the low to mid-20s. Skies clear from west to east with mostly clear skies expected shortly after sunrise. Dry conditions will persist tomorrow with diurnal heating bringing temperatures into the low 40s. .LONG TERM...(Tuesday night through Monday) Issued at 301 PM CST Mon Jan 22 2018 Weather pattern quiets considerably for the extended period as temperatures slowly moderate into the late week. A weak passing shortwave trof Tuesday night shifts winds around to the west then southwest for Wednesday. After a night of lows in the 20s, highs rise into the upper 40s, with lows the following night holding in the upper 20s to low 30s as southwest surface winds continue. By Thursday and Friday, highs rise into the middle to upper 50s and lows rise to above freezing by Thursday night. Upper trof that was more amplified in previous runs of both the GFS and EC for Friday has dampened, with resulting lesser impact on temperatures and lower rain chances for late Friday. Highs progged in the middle to upper 40s for the weekend behind the passing upper trof, which is still above normal for this time of year. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 540 PM CST Mon Jan 22 2018 Timing of ending of precipitation and cloud trends are the main challenges. HRRR is largely in step with with radar trends in shrinking and weakening of snow as the deep system exits the central Plains. There is a trend toward a shallow stratus deck lingering into the last half of this forecast, but too little confidence in this given upstream observations to extend MVFR cigs yet. && .TOP WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 6 PM CST this evening for KSZ008>011-020>023-034>038. && $$ SHORT TERM...Heller LONG TERM...67 AVIATION...65