Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/21/17

Area Forecast Discussion
National Weather Service State College PA
1055 PM EST Mon Feb 20 2017 .SYNOPSIS... An extended period of mild weather with well above normal temperatures is expected through the end of the week. A weak cool front will push through the state late Tuesday and Tuesday night. A stronger cold front is expected for Friday into Saturday. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... Expect fair weather overnight with increasing cirrus, as upper level ridge axis shifts eastward from the Grt Lks. At the surface, a dying back door cold front is over the central mountains at 03Z, with markedly lower dewpoints behind this boundary across the eastern half of the state. Mostly clear skies and drier air should result in the best radiational cooling across the eastern counties, where min temps have been adjusted downward slightly. Euro Ensemble MOS and latest HRRR support this idea of slightly lower temps, with mins ranging from 25-30F across the Middle Susq Valley/Poconos, to the mid 30s over the Laurel Highlands. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... A weakening front and the associated shearing upper shortwave will bring increasing high clouds to the area Tuesday, likely resulting in max temps several degrees cooler than those of Monday. A few showers may work into the northwest mountains toward evening, ahead of the weakening shortwave over the Grt Lks. Otherwise, confidence is high for another dry day across the remainder of central Pa. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... Gradually milder temperatures will return for the extended period as no genuine cold air push is in sight. High temperatures in general will be 10 to 20 degrees above normal with min temperatures mainly above freezing. Upper ridge axis is forecast to be located east of the state Tuesday night. The weak cold frontal boundary will produce a brief period or two of showers for late Tuesday (Northwest) and over the Central and Eastern parts of PA Tuesday night into the mid morning hours of Wednesday. Clouds associated with this weak frontal boundary will help to suppress temps a bit (but they`ll still remain well above average). The flow turns back to the SW by Wednesday causing temps to rebound. The overall, large-scale pattern becomes more amplified late in the week as a system over the central plains deepens and lifts into the Great Lakes. Clouds will increase Thursday and Friday with warm front lifting through, and bringing increasing rain chances heading into the weekend. && .AVIATION /04Z TUESDAY THROUGH SATURDAY/... Looking back to last night, no low clouds were noted at BFD or JST. Some fog at JST. For tonight into Tuesday, just some high clouds prior to 00Z Wed, as high pressure with dry air remains over the region. Some showers late Tuesday evening into early Wednesday, as a weak cold front moves across the region. Outlook... Wed...A.M. sub-VFR possible NW 1/3; otherwise VFR/no Sig Wx. Thu...Sub-VFR possible with chance rain showers. Fri...Sub-VFR possible with rain showers likely Friday night. LLWS probable. Sat...strong cold to bring Sub-VFR and possible thunderstorms. && .CLIMATE... Summary of record highs from 2/18 and 2/19... Harrisburg: Record high of 69 degrees on 2/19. Previous record high was 66 degrees set back in 1997. Williamsport: Record high of 69 degrees on 2/19. Previous record high was 60 degrees set back in 1997 Altoona: Record highs of 64 degrees on 2/19 and 66 degrees on 2/18 (tie). Previous record highs were 61 in 1994 (2/19) and 66 in 1981 (2/18). Bradford: Record high of 62 degrees on 2/18. Previous record high was 56 degrees set back in 1994. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte NEAR TERM...Fitzgerald SHORT TERM...Fitzgerald/La Corte LONG TERM...Lambert/Gartner AVIATION...Martin CLIMATE...
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
657 PM EST Mon Feb 20 2017 .AVIATION... Thin coverage of high clouds will continue during the evening and then begin to thicken overnight ahead of the next frontal system. This will be accompanied by southeast surface wind holding in the 5 to 10 knot range which is expected to keep LLWS on the marginal side tonight through Tuesday morning. Low pressure parent to the cold front will be well north over Hudson Bay during Tuesday and moving away from the Great Lakes. The trailing cold front that is left behind continues to exhibit signs of weakening in model data as it approaches SE Michigan. MBS has the best chance of MVFR rain showers from about mid morning through early afternoon although MVFR ceiling is expected to hang on through the day over the rest of the area. The frontal wind shift will likely dissipate and leave light southwest flow over the region by Tuesday evening. For DTW... Easterly flow lingering around the 100 degree direction during the evening will veer toward the south overnight with speed 10 knots or less. The veering trend will at least help switch runways back to southwest traffic operations by morning. VFR will otherwise persist until the remains of the cold front arrive during Tuesday afternoon. //DTW THRESHOLD PROBABILITIES... * None && .PREV DISCUSSION... Issued at 315 PM EST Mon Feb 20 2017 DISCUSSION... Record setting upper level ridge (574 DAM at 500 MB per 12z DTX sounding) in place over Southeast Michigan Today, but backed surface flow out of the southeast holding temps in the 50s this afternoon. Upper level ridge axis will continue to slide East, reaching the East Coast Tomorrow. Rather narrow upper level trough over Central North America, to break off into two pieces, as 500 mb cutoff low develops over southern Mississippi River Valley, with northern stream energy lifting through western Great Lakes Tonight into Ontario Tomorrow. Narrowing moisture Axis and weakening nature of the front draws into question the rain chances over southeast Michigan, as bulk of upper level forcing and low level jet lifts north of the CWA. Still, it appears there will be enough low level convergence for some light showers (likely) to hold together on Tuesday as the front moves across the area, as Local SREF weighted probabilistic guidance suggest pops around 70 percent are justified across most areas. However, 12Z HRRR gives one pause, as front comes through mainly dry with lack of instability. Regardless, does look like bulk of shower activity arrives after 12z, and will be trimming pops for Tonight, and a bit for tomorrow. Clouds and showers working through during peak heating will limit maxes, but still expecting temps around 60 degrees. Another surge of warm air on Wednesday with increasing southwest low level flow as low tracks through Lake Superior. 850 mb temps progged to rise back to around 10 C over southeast Michigan, with lower teens at 925 mb level, supporting highs well into the 60s to potentially 70 degrees at the high end. However, there is some concern in the development of low clouds Tuesday night into Wednesday morning behind tomorrow`s frontal passage, but suspect models over doing the low level moisture just a bit, especially if rain is very light tomorrow or does not materialize, and planning on skewing the forecast on higher end of guidance, mid to upper 60s. With the higher chance of low clouds in the south, along with the surface flow potentially more southerly vs southwest, would subsequently favor Flint Vicinity to be the warmest location during the day. Well above normal temperatures will continue through the end of the week before cooler air works in bringing temps back down closer to seasonal for this time of year. The main issue in the extended is the strong storm system that models are showing coming up from the plains for Friday and into the beginning of the weekend. Chances for precipitation are expected to increase by later in the day on Thursday as the warm front approaches. Currently, the low is advertised to move northeast over the central Great Lakes area keeping Southeast Michigan in the warm sector. A chance for thunderstorms will be possible as well as gusty winds as the cold front slides across the area this weekend. Conditions then look to dry out for a brief time to round out the weekend as high pressure settles in to the south. MARINE... East-southeast winds will continue to increase this afternoon and persist into Tuesday morning as strong high pressure retreats to the eastern Great Lakes. A frontal boundary will approach the western Great Lakes. Warm air above the cold lake surface will keep fairly stable conditions. Nonetheless, the gradient will increase with a long trajectory over the lakes. This suggest winds will become rather gusty tonight. Gusts in the 25 to 30 knot range knots are forecasted across much of Lake Huron tonight. A cold front will slowly move across Lower Mi and Lake Huron on Tuesday. There will be substantial weakening in the winds as the broad frontal boundary moves into the region. Further weakening of the post frontal gradient will support light and variable winds Tues night. Modest southwest winds are then forecast to develop on Wednesday. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...Small Craft Advisory from 10 PM this evening to noon EST Tuesday for LHZ441. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....BT DISCUSSION...SF/SS MARINE.......CB You can obtain your latest National Weather Service forecasts online at
Area Forecast Discussion
National Weather Service Grand Forks ND
941 PM CST Mon Feb 20 2017 .UPDATE... Issued at 941 PM CST Mon Feb 20 2017 Still waiting to see when and where potential dense fog may develop. Most hi-res and MOS guidance continues to support the development of fog tonight as winds become light within an environment of high low level moisture. This scenario makes sense, although coverage and how dense remain questions. Also, mid-cloud moving in from the west may limit fog potential. Give the mid- cloud, went higher coverage east of the valley. Most areas will be near or slightly below freezing, potentially adding to the impacts (icy roads?). Lots of uncertainty still. && .SHORT TERM...(This evening through Tuesday) Issued at 311 PM CST Mon Feb 20 2017 Precip winding down and additional fog formation tonight will be the main headaches for the period. The main upper trough continues to lift quickly through the Plains states, with the surface trough axis currently moving into our MN counties. The central CWA has seen some break in the rain with dry slotting but there is still some rain to the west with the mid level deformation band. The RAP and to a lesser extent HRRR have a decent handle on rain trends, taking the trailing edge of the precip into MN in the next 2 to 3 hours with the rest of the rain exiting the far eastern counties by 03Z. At this point think an additional 1 to 2 tenths of an inch of rain are possible in spots but not everywhere. Clouds have already cleared out of western ND and the clearing line will begin to move into the western counties in the next few hours. The center of the surface ridge will pass by to our south so winds will not go completely light, staying from the west and then southwest later tonight. In addition, a weak shortwave approaching through the near zonal flow will bring some additional cloud cover later tonight to the northern counties. That shortwave could bring some precip clipping our far northwest later tonight but not expecting much of anything south of the international border. With recent rain and melted snow, there will be plenty of moisture and the west winds bring slight drying but not a lot. The SREF probabilities of visibility less than a mile are very high tonight, and many of the CAM models break out fog. Will keep a fog mention in some areas going but will stay vague on density. Followed along with the blend of guidance and have fog redeveloping overnight and moving eastward, but will have to watch visibilities closely. As for temperatures, some drier dewpoints moving in will help readings overnight fall into the mid 20s to mid 30s. Southwest winds become westerly again tomorrow and fog should burn off by mid morning. Cold air advection will hold off until Tuesday evening, so the abnormally warm highs will continue for Tuesday. Have highs ranging from the upper 30s north to upper 50s in the far south, with some records again on the chopping block. .LONG TERM...(Tuesday night through Monday) Issued at 311 PM CST Mon Feb 20 2017 Temperatures begin to drop Tuesday night from northwest to southeast as cold air moves in behind the cold front. The general pattern aloft remains zonal Wednesday, keeping us from plummeting all the way to seasonal normals until Friday and continuing to bring in relatively moist air. Several upper level shortwave disturbances move through Tuesday night through Wednesday night bring precipitation chances to much of the area. At this time, a general model consensus indicates scattered light snow showers along and north of Highway 2 Tuesday night and into early Wednesday. As a dry layer aloft gradually becomes saturated, precipitation will likely begin as snow in the north and rain in the south. Colder air moving in from the north will gradually transition precipitation to a wintry mix and snow Wednesday afternoon from north to south. However, the models differ significantly in the locations/types/amounts of precipitation with temperatures around the freezing mark in the central valley during the day. Some banding is indicated by a few models along and south of Interstate 94, but an overall temperature blend indicates that these heavier amounts would fall as mainly as rain Wednesday afternoon, if they did occur. The models do agree that precipitation chances will be out of eastern North Dakota by Wednesday night and would be entirely out of northwest Minnesota by Thursday morning. On Thursday and Friday, the models have been coming into agreement for the last few runs and generally indicate a Colorado Low system bringing heavy snow across the Central Plains. Fortunately, this system keeps us generally in dry northerly flow and is expected to bring less than an inch of snow across the far southern Red River Valley and adjacent portions of west central Minnesota. Temperatures Thursday will still remain slightly above normal. On Friday through Monday, we will return to near normal temperatures with highs in the lower 20s to middle 30s and lows in the single digits to middle teens. The forecast for the weekend looks mostly dry but cannot completely rule out some flurries over the weekend as a shortwave disturbance or two pass overhead. Looking into early next week, several models indicate a disturbance will bring precipitation chances Monday into Monday night, but there is low confidence in precipitation type, location, and amounts at this time. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 648 PM CST Mon Feb 20 2017 As the main weather system moves out most locations can expect a brief period of vfr conditions this evening. Devils Lake has already developed dense fog, and anticipate most locations to develop at least MVFR conditions tonight, with dense fog (LIFR) possible. Still uncertain with duration of any possible LIFR conditions. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...TG SHORT TERM...JR LONG TERM...BP AVIATION...TG
Area Forecast Discussion
National Weather Service Lincoln IL
847 PM CST Mon Feb 20 2017 .UPDATE... Issued at 840 PM CST Mon Feb 20 2017 Weak cold front over central Iowa was making slow progress east this evening with a band of showers and isolated thunderstorms along and to the east of the boundary. The leading edge of the showers was pushing across far west central Illinois with a track more to the north than east. Based on the current track and speed, the showers should approach the I-55 corridor around between 1 and 3 am. Models continue to suggest the slow moving boundary to our west will weaken as it tracks across our area Tuesday morning with the scattered showers moving out in the early afternoon across the east. Another very mild night over central Illinois thanks to the cloud cover and southerly breeze with most areas remaining in the low to mid 50s, threatening many record warm lows (see climate section below) across the central, east central and southeast Illinois. The current forecast has a good handle on the late evening and overnight trends with respect to the precipitation timing from west to east, as a result, no ZFP update will be needed at this time. && .SHORT TERM...(This evening through Tuesday) ISSUED AT 233 PM CST Mon Feb 20 2017 Earlier clouds/fog did not keep a damper on the unseasonably warm weather, as partly sunny skies have pushed temperatures into the upper 60s to mid 70s across the forecast area this afternoon. Gusty southerly winds of 25-30 mph is helping out as well. The large area of precipitation that was west of us continues to lift north-northeast this afternoon, as the frontal boundary edges eastward. A few echoes are scraping the Illinois/Iowa border, but surface observations indicate these are largely not reaching the ground. Water vapor imagery shows a nice moisture plume tracking ahead of the deep trough in the Plains, and our rain chances will mainly await this surge to moisten up the lower levels of the atmosphere, currently suggested in forecast soundings to take place mid-late evening. Latest high-res model guidance suggesting the rain may only make it as far east as I-55 by midnight, but have included some low chances east to I-57 late this evening, with the highest PoP`s there after midnight. Thunder threat appears to still be isolated and mainly west of I-55, although the RAP model has MUCAPE`s up to around 100 J/kg as far east as Champaign and Effingham after midnight. Temperatures will remain very balmy overnight, only falling into the mid 50s, which could set some record warm lows for the month. While the upper trough starts to move into the western parts of the state Tuesday morning, it will start to weaken as an upper low cuts off over eastern Texas. The front will fall apart as a result, and temperatures on Tuesday should still reach the upper 60s to lower 70s. The NAM/GFS suggest most of the lingering rain over the eastern CWA would be early in the day, but some showers may linger into afternoon as the trough passes. .LONG TERM...(Tuesday night through Monday) ISSUED AT 233 PM CST Mon Feb 20 2017 With the Mon night-Tue weather system east of the area, high pressure ridge will slide across the CWA Tue night into Wed. This will keep the area dry with continued southwest flow. This southwest flow will keep the near record to record temps in the area through the day Wed. Models look very similar with a weather system moving through the flow across the northern US and into the Great Lakes region Wed night. However, the trailing cold front associated with this system will be dry as it moves through the region. It will be the weather system developing in eastern CO and pushing out into the plains that will ultimately bring the showers and thunderstorms to the area for Thur through Fri. This next system will develop a warm front that will extend into central IL by Thursday afternoon. Showers are expected to begin developing along this boundary over central IL Thur afternoon. Amount of moisture return ahead of this system is in question right now, so will just have a chance of showers along the boundary. Potential for showers will increase during for the evening hours as the system strengthens some and moves northeast...causing the warm front to slowly lift northward. Models differ on amount and location of qpf during the evening and then overnight, but all agree that an increase in precip will occur during the night. Highest pops will shift to the north as well. Fri should bring an increase in moisture and continued warm temps ahead of the associated cold front. Models differ with timing of the cold front, with the ECMWF pushing the front quickly through the area, while the NAM and Canadian still have the front west of the area at 18z and then through the center of the CWA by 00z. The low pressure area associated with the system is also slower on the GFS and Canadian than the ECMWF. Despite the differences in speed of the front, all three models generate precip in the eastern half of the CWA Fri afternoon. So, higher pops warranted along the front Fri afternoon. In addition, with increased moisture, instability should be maximized ahead of the front during the afternoon, which should lead to thunderstorms being more likely. So, have increased pops for thunder as likely. The low pressure area will lift northeast across the state Fri night with some lingering showers in the east during the evening and then colder air coming in on the back side. This colder air will come around in the wrap around section of precip, so precip should go from rain to a mix of rain and snow, to all snow Fri night. The chance of snow will continue into Sat, but with temps warming into the upper 30s to the middle 40s across most of the area, the snow will change back to rain during the day. After a dry and cooler period Sat night more precip is possible Sunday afternoon and Sunday night. New runs of the extended models are differing with location and amount...if any...qpf in the area during this time frame, so will just keep the consensus forecast going for now. Then pops will increase as the next significant weather system moves into the area for Monday. All models agree on this, but differ on timing. So, consensus pops have likelies in the area during the day Monday. Temps the rest of the week will stay above normal with record highs still possible Wed through Friday. Sat temps will drop back down to around or just below normal during the day, with Sat night lows below freezing across the area. Temps will begin to warm back up to above normal beginning Sun and then continue into Monday. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 510 PM CST Mon Feb 20 2017 A frontal system out to our west late this afternoon will slowly make its way east along with the precipitation shield that is associated with it. VFR conditions are expected early this evening with a transition to MVFR cigs starting between 05z-09z time frame with the possibility for a brief period of IFR cigs along and behind the weakening cold front which is slated to push across the TAF area Tuesday morning. Forecast soundings suggest a return to VFR conditions from west to east after 17z with PIA and SPI the first to see the improvement with CMI seeing the VFR conditions by 21z. Surface winds will be southeast to south at 10 to 15 kts this evening with a few gusts up to 20 kts thru 03z...with winds diminishing to 10 kts or less after 03z. Look for winds to gradually switch into the west after FROPA with PIA and SPI seeing the wind shift in the 12-14z time frame. && .CLIMATE... Issued at 312 PM CST Sun Feb 19 2017 Record Highs / Record Warm Lows - Monday Feb 20th... Peoria........ 68 / 46 Lincoln....... 70 / 46 Springfield... 74 / 46 Champaign..... 71 / 45 Bloomington... 67 / 45 Decatur....... 70 / 47 Danville...... 70 / 48 Galesburg..... 64 / 41 Charleston.... 73 / 48 Effingham..... 68 / 54 Record Highs / Record Warm Lows - Tuesday Feb 21st... Peoria........ 69 / 46 Lincoln....... 69 / 45 Springfield... 69 / 48 Champaign..... 67 / 47 Bloomington... 69 / 46 Decatur....... 68 / 48 Danville...... 67 / 50 Galesburg..... 68 / 40 Charleston.... 71 / 52 Effingham..... 73 / 52 Record Highs / Record Warm Lows - Wednesday Feb 22nd... Peoria........ 71 / 51 Lincoln....... 71 / 52 Springfield... 71 / 53 Champaign..... 69 / 49 Bloomington... 70 / 53 Decatur....... 72 / 51 Danville...... 71 / 54 Galesburg..... 61 / 45 Charleston.... 71 / 52 Effingham..... 74 / 55 && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Smith SHORT TERM...Geelhart LONG TERM...Auten AVIATION...Smith CLIMATE...WFO ILX
National Weather Service Jackson KY
1032 PM EST Mon Feb 20 2017 .UPDATE... Issued at 1032 PM EST MON FEB 20 2017 Temperatures are now into the mid 40s in the colder eastern valleys. This is in line with updated forecast from earlier. This will put our final lows somewhere down into the mid 30s tonight for those valley locations. Elsewhere to the west, winds may stay a bit more mixed tonight, keeping temperatures from completely falling off, like in the east. Thus, a bit milder overnight for most areas in the west. No changes warranted at this time. UPDATE Issued at 705 PM EST MON FEB 20 2017 Temperatures have already started their steep descend into the low to mid 50s this evening in the eastern valleys. With the degree of dry air mixed down tonight, should not take much for temperatures in the deeper valleys to again reach into the 30s tonight. With his said, have lowered the eastern valleys well below current forecast values in the 40s. We will likely see at least some mid 30s by tomorrow morning. Given the colder temperatures forecast, also beefed up the fog a bit, again mainly for valley locations. Fog shouldn`t be as bad or as widespread as last night, so no plans to highlight the fog in the HWO. Just some thin cirrus drifting over the area overnight and this shouldn`t have much impact on the overall expected weather. && .SHORT TERM...(This evening through Tuesday night) Issued at 430 PM EST MON FEB 20 2017 21z sfc analysis shows high pressure shifting off to the northeast with deep low pressure taking shape over the Norther Plains. The pressure gradient between these is tightening up to the west. Here in eastern Kentucky, the winds are starting to respond to the passage of the high by turning to the southeast and south - but still rather light. Ample sunshine through high clouds helped to propel temperatures into the upper 60s and lower 70s. Dewpoints decreased a bit during the middle part of the day with a range from the upper 30s to mid 40s for most places. The models are in good agreement aloft through the short term portion of the forecast. They all depict a strong ridge moving from Kentucky east to the Southeast Coast tonight while a full latitude trough splits apart with its southern extent closing off over the western Gulf Coast. To the north of this developing low, the northern portion will cross into the Great Lakes while some energy runs out ahead of its trough axis and passes over Kentucky into Tuesday morning. The main axis - though weakening aloft - will make it into the state later in the day and slowly pass that night along with some small height falls - more substantial in the ECMWF. Given the general model agreement will favor a blended solution for the larger scale while leaning toward the HRRR in the near term along with the ECMWF for weather details from Tuesday through Tuesday night. Sensible weather will feature a rather warm evening with a moderate ridge to valley temperature split developing under variable amounts of high clouds and an inversion. Good drying and mostly sunny skies today should limit the fog formation tonight to just the valleys ahead of thicker clouds moving in towards dawn. For Tuesday showers will push in from the southwest by mid afternoon with plenty of clouds and mild conditions continuing. The best rain chances will be later that night as a sfc low passes by to the south coupled with the weak energy aloft. This will make for another warm night with some places probably seeing soaking rains - depending on the interaction of the departing 300 mb jet north of the state and any divergence aloft that it generates over our area. For the most part the blended model solution looked decent, though the NAM seems to cut off the western extent of pcpn shield quicker than the ECMWF and GFS on Tuesday night but this seems to fast so have not backed off on the blended solution here. Again used the CONSShort and ShortBlend as the starting point for the grids through the short term portion of the forecast. Did make adjustments to temperatures tonight to account for a decent ridge to valley difference but readings should be similar Tuesday night with the rain. As for PoPs, did adjust them for late Tuesday into the night - translating the higher PoPs across the CWA more cleanly. .LONG TERM...(Wednesday through Monday) Issued at 330 PM EST MON FEB 20 2017 The extended forecast period begins on Monday with a deep closed upper low tracking northeast through the spine of the Appalachians. As this feature tracks northeast, blocking over the New England and Canadian Maritime region will hinder the exit of the back edge precip moving through eastern Kentucky. This slow exit followed with the approach of the colder air in behind on Monday night into Tuesday may lead to a brief mix of rain and snow on top of Black Mountain. In addition to this, models have been coming into more agreement of a prolonged heavy rainfall event coming to an end Monday evening into Monday night across eastern Kentucky. Some lingering minor flood problems may be possible, if not just some rivers running full. Both the Euro and GFS seem to have come to an agreement on this with the Euro being slightly wetter. Will keep this mention in the HWO. Heading into the midweek time frame, a brief period of ridging moves into the OH valley with a period of drying as southwest flow increases ahead of the next incoming cold front. High temps on Wednesday will climb into the upper 50s to low 60s with SW 10 to 20 knot winds bringing in an unseasonably warm airmass. In fact, models are suggesting an overall drying trend to the approaching front with the bulk of the moisture to the north over the Midwest and into Ohio. Little if any precip is expected with this feature. Passage of the front on Wednesday night will bring in a colder airmass to the region by Thursday with a possible prolonged upslope event taking shape for Thursday and Friday. At this point the pattern brings in a longwave trough across the eastern CONUS into the weekend. The northwest flow then brings a series of disturbances in an upslope scenario. At this point, while the models hint at temps being warm enough for rainfall during the day and snow showers overnight, an upslope event with the correct wind component would mean some convection and snowfall at warmer temps. For now, went with a general snowfall at 34 degrees and below due to the uncertainties in the models but this may need reevaluated. The general trend is cooler towards the end of the extended but models have backed off from the depth of the cold air. Due to this, will leave any mention of snow out of the HWO as none is expected to be impactful at this point. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) ISSUED AT 705 PM EST MON FEB 20 2017 VFR conditions will continue through 00z Tuesday evening. Cloud bases will start to come down through the day tomorrow, but any lower MVFR cigs should hold off until after 00z. Some light rain could move into the area late in the period, but confidence is low on the arrival time of this precipitation. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...KAS SHORT TERM...GREIF LONG TERM...SHALLENBERGER AVIATION...KAS
Area Forecast Discussion
National Weather Service Marquette MI
725 PM EST Mon Feb 20 2017 .SHORT TERM...(This evening through Tuesday) Issued at 356 PM EST MON FEB 20 2017 Strong upper trough is pressing across northern Plains with sfc low lifting over southern Manitoba. Strong moisture advection with pwats over 1 inch (a whopping 300-400+ percent of normal) surging in ahead of the sfc trough is resulting in widespread showers and a few clusters of tsra lifting toward Upper Michigan from the central Mississippi river valley. RAP and HRRR matching reality well and show showers moving over western cwa through late this aftn then spreading to central cwa this evening and into far east cwa by late evening. Have seen isold lightning strikes every now and then with showers over eastern IA into western WI where RAP and NAM showed elevated MUCAPE up to 100j/kg and based on the forecast instability this evening could see isold tsra potential this evening as showers slide across. Given the unusually high moisture lifting in and the elevated instability could see heavy downpours as the rain moves through. As shortwave lifts across Upper Great lakes and sfc trough crosses the region, showers should shift steadily west to east across Upper Michigan. High res guidance including the NAM, HRRR, RAP and NSSLWRF indicate that there will be brief break with initial showers and then there may be another push of showers move through on the sfc trough axis. Given steeper h85-h5 lapse rates near 7c/km moving in with surge of mid level drying think best chance of tsra could actually occur 05z-07z Tue over west, 08z-11z Tue over cntrl and over east cwa 11-13z Tue. Effective shear up to 50 kts with wbzero heights lowering to 7k and 50 dbz height for 1 inch hail of lower than 20kft suggests that if storms can form overnight, there would be risk of hail. On into Tue. Once showers and possible isold tsra exit eastern cwa early in the day should see column dry out quickly from west to east. Breezy on the Keweenaw and those stronger winds are sign of better mixing depth that will spread over rest of cwa. As main trough exits east, low-level winds will start out west then shift to the southwest ahead of another weaker low pressure system sliding over northern MN. Overall mixing to 900-875mb supports highs well into the 50s over much of cwa expect where winds are onshore. May even see readings top out in the low 60s for interior west and central. For now, increased temps to near 60F to come more into line with better perfoming guidance with recent warm spell. Any showers with the northern MN wave should stay west of cwa through late in the aftn. Thus far with the warm up rivers have not responded much likely due to gradual melt as nighttime lows have dipped near or blo freezing. Rivers should respond tonight into Tuesday though more significantly as mins tonight will remain above freezing and with rainfall and melting snow tonight and since readings spike into the 50s on Tue. Overall the rivers should see their greatest rises in the next few days. At this time, significant hydro issues are not expected due to lower river and stream levels, overall lower than normal amounts of water equiavalent in the snowpack and generally quick moving rainfall tonight with total qpf staying mainly less than 0.75 inch in most areas. Still some unknowns though including extent of ice on rivers. At the least with the rain and melting snow tonight could see ponding of water in low-lying/poor drainage areas, especially if there is any ice/snow plugging up storm drains. Will mention this potential in HWO. .LONG TERM...(Tuesday night through Monday) Issued at 246 PM EST MON FEB 20 2017 Beginning Tue night...A weak shortwave moving through the area and the presence of a frontal boundary could produce some sprinkles/drizzle over mainly the northern tier of the forecast area. Otherwise, expect dry conditions. Most of the models continue to trend stronger with a shortwave moving through the area late Wed into Wed night. The 12z NAM and ECMWF favor a sfc low track over the western CWA which makes sense given the trend toward a stronger solution. The 12z GFS meanwhile remains weaker and farther se bringing the swath of best pcpn through Iron and Marquette counties. If the western solution of the NAM/ECMWF does work out, not much precip will fall across the CWA and it will be mostly confined to the far west and the Keweenaw. Most of the pcpn would be rain or a mix or rain/snow and possible fzra. Will have to watch this time frame as there remains plenty of uncertainty. Attention then turns to Fri into Sat as models continue to bring a strong low pressure system SE of the CWA. While there continues to be uncertainty on track/timing of the sfc low, there is a general consensus that the low will track through central Lower Mi late Fri into early Sat. Model disagreement may increase over the next few runs as is normal in this scenario until the shortwave associated with the system moves onshore late Wed. Given the current track of the GFS, ECMWF and GEMnh, all or most of the CWA will see snow, with moderate to possibly heavy snow over the north-central U.P. where upslope and lake enhancement from h85 temps between -10 and -15c will increase synoptic amounts. Blowing snow would also be an issue, especially near Lake Superior. Will need to keep an eye on model trends with this system over the next few days. The weekend will see h85 temps continue to fall with LES likely in the NW-WNW snow belts. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 724 PM EST MON FEB 20 2017 Conditions will continue to deteriorate this evening with widespread moderate rain ahead of a low pressure trough. Expect conditions to fall to IFR at all terminals, even to LIFR at KSAW and KIWD later tonight. Even with winds becoming gusty, persistent low- level inversion will allow for LLWS into the late evening as strong low- level jet ahead of approaching trough translates across the area. After trough passes tonight, there is uncertainty in how quickly low clouds will clear out. With upslope westerly winds, will plan for low clouds to hang on through the night but with some improvement to MVFR late. By mid morning on Tue, VFR conditions will dominate with gusty westerly winds, especially at the more exposed KCMX location. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 356 PM EST MON FEB 20 2017 Tighening pres gradient btwn high pres ridge shifting toward the E Coast and an approaching low pres trof will result in SE gales of 35- 40kt thru much of tonight across the e half of Lake Superior. Gales will end with the passage of the trof late tonight. Winds should then stay mostly 25kt or less Tue thru Thu. Stronger winds, perhaps gales, are expected later Fri into Sat as a low pres system tracks ne thru the Great Lakes region. After a hiatus from winter type conditions, should also the potential for freezing spray return later Fri into Sat. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... Gale Warning until 1 AM EST Tuesday for LSZ264>267. Lake Michigan... None. && $$ SHORT TERM...JLA LONG TERM...Voss AVIATION...JLB MARINE...JLA