Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/31/19

Area Forecast Discussion
National Weather Service Huntsville AL
827 PM CDT Wed Oct 30 2019 .NEAR TERM...(Tonight) Issued at 827 PM CDT Wed Oct 30 2019 Low clouds, drizzle and a few showers are still occurring in between MCSs. The northern extent of the next MCS in MS will produce light to moderate rain in northwest AL shortly. Have removed thunderstorms and added drizzle through 06Z. Stronger thunderstorms in central and southwest MS have been progged to lift northeast into west central and north AL after 08-09Z. This as a low level jet of 40-50kt develops within the RRQ region of the upper jet that begins to pivot with the upper trough into the lower OH/MS valleys late tonight. This will aid a mesolow associated with the convection in southwest MS to develop and ride northeast along the cold front. Earlier convection has lowered convective instability over central and north AL for the time being. However, southerly flow increasing later tonight will advect dew points around 70 northward into the area. This may enable a nose of 300-500 j/kg CAPE to reach north AL and southern middle TN very late tonight as the mesolow and QLCS approach. Several successive HRRR runs have indicated a stronger cell or cell cluster with the mesolow moving with the low into north central or northeast AL from 10-12Z. This as 1km SRH values increase again to above 300 m2/s2. Thus, will maintain the risk of damaging wind or even a tornado in our HWO and impact graphics. .SHORT TERM...(Thursday through Friday) Issued at 250 PM CDT Wed Oct 30 2019 A strong to severe thunderstorm in extreme northeastern Alabama cannot be ruled out just after daybreak around 8 or 9 AM, but otherwise just expecting lingering rainfall behind the front. With cloud cover lingering and cold air advection behind the front, temperatures will likely only not move much on Thursday due to the effects of cloud cover and cold air advection. Cloud cover should finally move east out of the area in the late afternoon or very early evening hours on Thursday. With light winds expected behind the front overnight and dewpoints dropping into the upper 20s to around 30 degrees, widespread frost or freezing temperatures between 28 and 32 degrees look possible by Friday morning. Therefore, have issued a Freeze Watch that is in effect for all of our northern Alabama and southern middle Tennessee counties from 12 AM midnight on Friday through 9 AM. With this much colder start to the day and some continued weak cold air advection, highs will be much colder despite abundant sunshine only reaching the lower to mid 50s. .LONG TERM...(Friday night through Tuesday) Issued at 250 PM CDT Wed Oct 30 2019 A strong ridge of high pressure centered across the Deep South region will reinforce a much cooler and dry air mass this weekend. This will result in mostly sunny, but cool, crisp days with highs peaking in the mid to upper 50s to kick off the month of November. Clear nights with calm winds will allow for good radiational cooling and potentially additional nights with a light freeze (with lows in the 28 to 32 degree range), with widespread frosts each morning. The upper-ridge will gradually slide to the northeast into the Mid Atlantic region by Monday and Tuesday. This will help develop a SE/S flow off the Gulf of Mexico which will help to advect some moisture back into the region. We`ll also see an uptick in temperatures as highs climb back into the 60s during the day. A few isolated showers may be possible Tuesday afternoon and evening as a weakening front approaches the area. However, most locations will remain dry for much of this period and the upcoming week ahead. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 639 PM CDT Wed Oct 30 2019 An active overnight and early morning period in store for both terminal locations. Shower activity is expected to pick up near the KMSL terminal within the next couple of hours, and by midnight at KHSV. Vsbys and cigs remain a challenge, and amendments may be needed as several fluctuations are likely through the overnight hours. Both terminals could drop as low as LIFR vsbys, which has already occurred for a short period of time at KHSV. Expect the heaviest shower and thunderstorm activity to occur before or right around sunrise, and these storms could be accompanied by strong winds. Expect strong gradient winds behind the frontal passage tomorrow, with sustained winds of 15kts and gusts up to 25kts beginning around sunrise and lasting through the end of the TAF period. Expect MVFR/IFR cigs to clear by sunset on Thursday. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...Freeze Watch from late Thursday night through Friday morning for ALZ001>010-016. TN...Freeze Watch from late Thursday night through Friday morning for TNZ076-096-097. && $$ NEAR TERM...17 SHORT TERM...KTW LONG TERM...AMP.24 AVIATION...25 For more information please visit our website at
National Weather Service Wilmington OH
1004 PM EDT Wed Oct 30 2019 .SYNOPSIS... Strong low pressure will travel through the Ohio Valley today through Thursday, bringing widespread showers. Colder temperatures and strong winds will follow the storm system Thursday night. Dry and chilly weather is forecast for Friday and continuing through the weekend under high pressure. && .NEAR TERM /THROUGH THURSDAY/... Steady rain is moving off to the east for now, with patchy showers and drizzle expected through around 08Z, before additional steady rain begins to move in from the southeast. With this part of the forecast roughly behaving as expected, attention was primarily given to fog potential overnight. Along a corridor including several counties on either side of the KY/IN border, stretching as far northeast as Oxford OH, visibilities have been dropping below 1SM. This is currently being handled quite well by HRRR visibility projections, in an area where low-level theta-e is pooling on the warm side of a frontal boundary. This front is somewhat ill-defined in terms of wind flow, but those light and variable winds are certainly one factor helping the fog to develop. However, it remains somewhat unclear just how dense this fog will get -- with a pretty solid expectation of visibilities in the 1SM-3SM range, but not as much confidence in any prolonged period of 1/2SM or below. The trend on the HRRR has been to gradually shift the worst of the visibilities eastward with time, keeping the far northwestern ILN CWA generally out of the worst of it, and moving the lower visibilities into central Ohio by 06Z. Still very possible that a dense fog advisory may be needed, but it would be good to make sure that it isn`t going to be a situation where an observation site begins improving again after just an hour or two. A quick look was also given to wind gust potential tomorrow afternoon/evening. There is certainly some support (especially from the GFS) for winds approaching advisory criteria near/north of Interstate 70, but enough uncertainty from a few other models to not want to go out with a headline until a full run of 00Z products becomes available. Previous discussion > The cold front that slowly moved through last night has begun to stall as pressure falls over the Ohio Valley are promoting increased easterly flow. Along the front, moisture advection from the southwest and a subtle wave of low pressure are resulting in periods of showers this afternoon and these will continue into the evening hours. With the wave exiting to the northwest late this evening, a few hours of dry weather during the overnight are expected. Additional pressure falls occur over the Ohio Valley overnight with a deepening trough moving in from the east. Moisture increases once again, resulting in additional showers Thursday morning as the cold front moves through. The main concern within the short term period will be associated with the stationary front moving back to the northwest overnight. While the rain may cease for a time, low cloud ceilings and enhanced surface moisture favors the development of areas of fog by as early as this evening. How dense the fog will ultimately be and how widespread is still quite uncertain. As of 2 PM, observations in Dayton and surrounding ares are observing limited visibility as convergent winds and saturated air results in fog/haze. Light to moderate rain is also a contributing factor but confidence is increasing that the fog will not clear after the rain has cleared. Highest confidence is currently from Cincinnati through Dayton metro areas along the front. A dense fog advisory may be required as early as this evening depending on how quickly conditions worsen. Further southeast, fog is also expected to develop but it may not be quite as dense. After temperatures reach their peak this afternoon, temperatures will struggle to fall overnight with the battle between warm air to south and cooler air to the north. Temps will vary in relation to the boundary with the forecast to range from the low 50s northwest to the low 60s southeast. && .SHORT TERM /THURSDAY NIGHT/... Showers are likely overspreading the area once again Thursday morning ahead of an approaching cold front. A deepening area of low pressure over the southern Great Lakes moves northeastward throughout the afternoon, providing active weather during the short term period. High temperatures for the day occur during the morning hours as the warm sector covers much of the forecast area. As the low deepens and reaches Northwest Pennsylvania, showers will diminish in coverage with the cold front moving eastward. Strong winds will develop in the very tight pressure gradient following the low. Latest guidance shows gusts over 30 knots late Thursday afternoon as direction shifts from south to west behind the low. The west winds will usher in sharply colder temperatures Thursday afternoon. Late Thursday night, wrap around moisture presents a brief opportunity for rain/snow showers, primarily north of I-70. With warm surface temperatures, no accumulation is expected at this time. Temperatures continue to drop into the upper 20s Friday morning, with a Freeze Watch currently in place. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... High pressure will be building in from the southwest on Friday as zonal flow aloft slowly becomes southwest as a deepening l/w trough in the central U.S. deepens Friday night. The surface high crosses east of the Ohio Valley late Friday and southwest flow will bring a slight return to warmer air but probably have a hard time scouring out the cooler air entrenched at the surface overnight. Friday will be the coolest day of the forecast with readings in the mid to upper 40s. The slight southwest flow expected overnight will warm things slightly for daybreak Saturday off of Friday morning lows, but only marginally with readings still expected to drop below freezing everywhere. Saturday will be similar to Friday but could reach near 50 in parts of KY and the lower Scioto Valley. Increased cloud cover with the l/w trough crossing the region during the day will inhibit any real warming, and the brief flow from the south will then turn west. Sunday will see another high settle south-southeast of the region with northwest flow aloft keeping the region under a cool advection pattern. The upper flow turns more westerly overnight and then a gradual increase in temperatures will be found for next week. The next real chance of precipitation will be found Tuesday as a weak cold front crosses the region as an upper low digs into the upper midwest. Temperatures will be below normal until the work week starts and then hover near climo values. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... Steady rain will likely come to an end over the next hour or two, with occasional periods of showers or drizzle expected to continue through the rest of the night. Winds are also expected to become lighter as the evening turns into the overnight. There is high confidence that low ceilings (IFR/LIFR) and fog (IFR) will develop at all TAF sites, with some chance of dense fog (1/4SM) especially at KDAY/KILN/KCVG/KLUK. This TAF update will largely retain the pessimistic forecast through the overnight hours and into tomorrow morning. A very gradual improvement in ceilings is expected tomorrow, though IFR ceilings should persist for a while, becoming MVFR later in the day. Another period of showers (potentially heavy) is expected late morning / early afternoon, followed by drier conditions after that. Winds will be one of the main stories tomorrow, and they will pick up more markedly after the rain has ended, with gusts into the 30-35 knot range at all TAF sites. This is slightly higher than the previous forecast, and there is still a chance that these gusts may need to be increased again in future forecasts. OUTLOOK...MVFR ceilings may continue into Thursday night. Gusty west winds will also continue Thursday night, diminishing by Friday morning. MVFR ceilings are possible again Saturday night. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...Freeze Watch from Thursday evening through Friday morning for OHZ026-034-035-042>046-051>056-060>065-070>074-077>082- 088. KY...Freeze Watch from Thursday evening through Friday morning for KYZ089>100. IN...Freeze Watch from Thursday evening through Friday morning for INZ050-058-059-066-073>075-080. && $$ SYNOPSIS...McGinnis NEAR TERM...Hatzos/McGinnis SHORT TERM...McGinnis LONG TERM...Franks AVIATION...Hatzos
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
918 PM CDT Wed Oct 30 2019 .UPDATE... 918 PM CDT Somewhat of a complex forecast tonight into Thursday with mid- latitude cyclone developing/strengthening as it moves across the region. Strong mid-upper level jet nosing northeast from the southern high Plains into the mid-Mississippi Valley with evening RAOBS sampling 135kt at 250mb and 100kt at 500mb. Regional WSR-88d mosaic shows developing warm conveyor belt of precip beginning to blossom from southeast MO north into northwest IL. This development trend is likely to continue tonight as forcing strengthens and begins spread east taps into the northward surging moisture. This evening into the overnight hours anticipate this band of precipitation to increase in coverage and gradually move across the area. Precip type is tricky with a somewhat convective nature to the precip combined with lack of ice nuclei outside of the heavier precip likely to lead to hodge podge of precip types overnight. In the heavier showers, will likely see snow and some sleet over northwest portions of the CWA with mainly rain eastern CWA. Outside of the heavier precip elements, lack of ice nuclei will probably lead to more of a drizzle and snizzle as dominant p-type. Developing dry slot over MO will likely nose into the area late tonight into early Thursday morning, with again a loss of ice likely leading to a period of mainly drizzle/very light rain. Unfortunately, NAM and particularly RAP cross sections would support a period of potential freezing drizzle later tonight into early Thursday morning in the dry slot over portions of northern IL. Reluctant to make the forecast too complicated, but given the potential impacts of FZDZ think its probably worthy including in the updated forecast this evening. A lot will hinge on placement of sfc freezing line, but looks like the best FZDZ threat will be west of I-355 into north central IL, with mainly just drizzle east into heart of Chicago metro and rest of eastern IL and points eastward. Developing/strengthening deformation zone is then forecast to sweep across the area in the wake of the dry slot. Model forecast ascent within this deformation band is respectable, but nothing too extreme and unlike mainly mid-latitude cyclones, guidance suggests it will be relatively stable with rather weak lapse rates in the dry slot. Cross sections do show a bit of saturated negative EPV, but overall doesn`t appear to be a set up that really favors intense banded precipitation, but rather a 4-6 hour window of light to moderate snow. Surface temps will be falling during the day, especially western and central CWA where best accumulations look to be setting up and most impactful snow is expected. Snow will be fighting a bit with the high October sun angle to accumulate during the afternoon when the heart of the deformation band is over the Chicago area. Thermodynamically, conditions do appear moderately favorable for lake enhancement to the snowfall over northeast IL near the lake and does appear as though high res models are picking up on this and depicting a heavier band of snow in the simulated reflectivity. That heavier lake enhancement to the precip should help somewhat offset the unfavorable diurnal timing to the snowfall in northeast IL, though the milder temps near the lake will also tend to cut down on accumulations. Weighing all these potential factors and possible complications it really appears the going forecast has a good handle on potential accumulations and not planning any headline or meaningful changes to forecast accums this evening. The potential factors above certainly do highlight the possible factors which could result in forecast snowfall amounts being off, either too high if sun angle, marginal temps, lake warming are a bigger factor, or potentially locally higher amounts into NE IL if lake enhancement is more robust. Finally, do want to mention that I am a bit concerned about the potential magnitude of the lakeshore flooding into Chicago. Already seeing 7ft waves at the Wilmette Buoy and with northeast to north winds forecast to continue overnight through Thursday morning and strengthening further, expecting waves on the IL shore to build with waves probably peaking in the 10-12ft range. Really hard to know what magnitude of impacts 10-12 foot waves will have at these near record high lake levels given the lack of a solid historical database. Am concerned that lakeshore flooding could be worthy of warning, but given the unknowns will pass this concern to oncoming mid shift to watch. - Izzi && .SHORT TERM... 328 PM CDT Through Thursday night... We have issued a winter weather advisory for much of northern IL for tonight through much of Thursday for some accumulating snow. While we are quiet right now across the area, attention has turned to our west, where the main upper level storm system is now beginning to shift over the central High Plains of CO and western KS. This storm system is expected to shift eastward over the mid and lower Missouri Valley tonight. As it does so, surface low pressure will begin to consolidate over the Ohio Valley into early Thursday morning. It still appears that the orientation of the upper trough will gradually shift from a positive tilt (southwest to northeast orientation) to more of a neutral tilt (north to south) as it shifts over our area on Thursday. As a result, large scale dynamics with this storm system will be in the beginnings of ramping up as it moves over our area Thursday. This should support a more organized deformation zone over the area on Thursday as the lower level circulation begins to develop. For this reason, it appears that we will be in for some more accumulating snow for the area. The precipitation should onset over north central IL this evening, and while it could start as a mix of rain and snow, it will quickly transition over the snow. Snow should occur for much of the night over north central IL, with accumulations of 2 to 3" inches by early Thursday morning. Farther east towards the western Chicago suburbs the precipitation will onset as rain, but we will see a gradual change over to snow from west to east tonight. The western and northern suburbs of Chicago could see the change over to snow by midnight, but in the City the snow change to snow will likely hold off until around daybreak Thursday due to lower near surface temperatures. Areas over northwestern IN are likely not see the transition to snow until mid to late Thursday morning. Once we transition to snow expect periods of light to moderate snow to continue into Thursday afternoon before it gradually ends from west to east during the mid to late afternoon. Total snow accumulations still look to be the highest over north central IL, where some totals could push close to 6". These amounts should tapper off towards the western suburbs of Chicago into the 2 to 5 inch range, and likely down to an inch or less in the city itself and into northwestern IN. Winds will also become gusty up to 35 mph from the north-northwest during the day Thursday, and this could result in some blowing snow in open areas. Otherwise, lake shore flooding continues to be a concern later tonight and on Thursday as waves build to around, or just above 10`. KJB && .LONG TERM... 328 AM CDT Friday through Tuesday In the wake of this system, expect a hard freeze (temps falling into the upper 20s) area-wide into Friday morning. Otherwise, below average temperatures are likely to continue through the weekend as another upper trough and surface cold front brings a reinforcing shot of cool air to the area. Some clipper type systems could result in some changeable temperatures and on and off again small chances for precipitation going into next week. However, at this time no changes were made to the general blended forecast. Carlaw/KJB && .AVIATION... For the 00Z TAFs... 648 PM...Multiple forecast concerns including... Light rain through early morning...chance of snow/sleet. Period of moderate snow mid Thursday morning/early afternoon. Ifr cigs through Thursday afternoon. Strong northerly winds tonight shifting northwest Thursday. Pockets of light and drizzle this evening will transition to a more widespread light rain with scattered heavier showers and these will likely have heavier precipitation rates allowing for precipitation to mix/changeover to snow and perhaps have some sleet mixed in. Precip is likely to change over to all snow for northwest IL and rfd by late evening with light snow already being reported in parts of eastern IA. While confidence is low...there may be a lull in the precip prior to daybreak for the Chicago terminals where prevailing precip may remain light rain or drizzle. But there is good agreement among the most recent models of a band of snow slowly moving across all of northern IL Thursday morning...ending from west to east during the early afternoon. Confidence is increasing that there could be a period of snow across much of the area with visibilities below 1sm and possibly into the 1/2sm range for at least a few hours. But only medium confidence at this time and opted to only tempo 3/4sm for the Chicago terminals. Changes to both lower vis and cigs are possible with later forecasts. The snow will taper off during the early/mid afternoon and should be finished by sunset for ord/mdw. Prevailing ifr cigs are expected to continued through late Thursday afternoon when cigs will lift to mvfr and then scatter out. Ifr cigs will spread back across northern IL and rfd later this evening. Its possible there could be some lifr cigs with the heaviest snow. North/northeast winds currently will turn northerly this evening and then turn north/northwesterly overnight with gusts into the lower/mid 20kt range. Winds will slowly turn more northwesterly by Thursday afternoon. Speeds and gusts likely to increase during the late morning with gusts into the 30-35kt range possible from early afternoon through early evening with speeds/gusts quickly diminishing by mid evening as winds turn more westerly. cms && .MARINE... 331 PM CDT Winds expected to steadily increase this morning through this afternoon and tonight, as low pressure lifts across the Ohio Valley and into the central Great Lakes. The current northeast winds of 10 to 20 kt are expected to increase to 20 to 25 kt this afternoon and then to 30 kt tonight. These strengthening onshore winds and building waves will produce hazardous conditions for small craft, with an extended period of these similar conditions expected into Thursday night. As the low draws near tonight into Thursday morning, it is appearing that gales will develop across the southern half of the lake and nearshore waters, and have updated the Gale Watch to a warning for Thursday into Thursday evening. It`s quite possible that these gales start a little sooner for the IL shore, and then possibly last longer into Thursday night for the IN shore. Rodriguez/KB && .LOT WATCHES/WARNINGS/ADVISORIES... IL...Winter Weather Advisory...ILZ006-ILZ012-ILZ019-ILZ020-ILZ021- ILZ032...midnight Thursday to 6 PM Thursday. Lakeshore Flood Advisory...ILZ006-ILZ014...1 AM Thursday to 4 PM Thursday. Winter Weather Advisory...ILZ013-ILZ014...3 AM Thursday to 6 PM Thursday. Winter Weather Advisory...ILZ003-ILZ004-ILZ005-ILZ008-ILZ010- ILZ011 until 4 PM Thursday. IN...Lakeshore Flood Advisory...INZ001-INZ002...10 AM Thursday to 1 AM Friday. LM...Gale Warning...LMZ740-LMZ741-LMZ742...10 AM Thursday to 7 PM Thursday. Small Craft Advisory...nearshore waters until 10 AM Thursday. Gale Warning...LMZ743-LMZ744-LMZ745...10 AM Thursday to 10 PM Thursday. && $$ 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 Saint Louis MO
923 PM CDT Wed Oct 30 2019 .UPDATE... Issued at 923 PM CDT Wed Oct 30 2019 At 9pm, surface temperatures have fallen a bit quicker than originally anticipated, with sub-freezing temperatures around 30 degrees for much of Knox, Shelby, and Lewis counties. KUIN has fallen to 32F and KCOU to 34F. It is for this reason, along with light precipitation already occurring, that the Winter Weather Advisory was moved up to begin early this evening. IR satellite imagery has been helpful at evaluating cloud ice potential through sampling of cloud top temps, and indeed cloud tops have cooled to below -10C for many areas N and W of the STL metro area thanks to at least a partial seeder-feeder effect from cold cloud tops advecting from OK this evening. This has resulted in snow onset a bit earlier for KUIN and likely in central MO imminently, but will probably only be temporary, as these colder cloud tops are expected to move out by 04z. At that point, the original cloud ice forecast still looks mostly on track. Colder surface temps and a period of colder cloud tops will result in a bit more snow forecast than earlier and less icing from freezing rain--with the biggest change occuring in portions of northeast MO where amounts approaching 3-4 inches of snow will be possible with little or no ice accretion. Elsewhere, the forecast largely remains on track for snow and ice amounts. It needs to be emphasized that the snow forecast is for grassy surfaces with roads expected to receive less. The current Advisory area still looks good taking into account the road consideration. Another notable thing is the blustery conditions that will develop later tonight and continue into Thursday with sustained winds of 15-20 mph and gusts to 30-35 mph at times. For areas that receive a few inches of snow in northeast MO and west-central IL, this could create additional issues with regard to blowing and drifting snow especially on rural roads. Finally, the RAP shows an area of modest 100-200 MUCAPEs south of STL metro, with this expanding into southwest IL this evening before exiting. Sure enough, a CG or two have been seen thus far in this area. An isolated thunderstorm will be possible in these areas. TES && .SHORT TERM... (Through Late Thursday Night) Issued at 336 PM CDT Wed Oct 30 2019 This is a complex forecast over the next 12 -18 hours across the area. The expectation is for light rain to breakout by early this evening as a midlevel disturbance ejects eastward out of the lee of the Rockies. The precipitation will eventually changeover to snow from northwest to southeast overnight into early Thursday morning as the temperature profile rapidly cools in the 700-800 hPa layer. However, there likely will be at least a brief period of time where there is a lack of cloud ice nuclei aloft and surface temperatures drop below freezing. This situation would produce light freezing rain, with a light glaze expected. This is most likely this evening across portions of northeast Missouri where upstream infrared satellite imagery depicts cloud top temperatures mostly in the -5 to -10C range. These cloud top temperatures likely will not be cold enough to support the introduction of ice. The light snow should wind down late tonight and into the early morning hours with lingering flurries possible for several hours. Snowfall accumulations will take place mostly across the northwestern third of the CWA with the heaviest accumulations (1-3") from near Kirksville ENE toward Canton. Have issued a winter weather advisory for these locations as there is expected to be several hours of light snow falling with temperatures falling through the upper 20s. Therefore, travel conditions may deteriorate as road temperatures fall toward the freezing mark. The other story is the anomalously cold conditions. Widespread near or below freezing temperatures are expected tonight so no changes made to tonight`s freeze warning. Temperatures through midday will likely remain steady, with only a slight rebound in the afternoon. Highs should only be in the mid to upper 30s, which is about 25-30 degrees below normal! In fact, all three of our climate sites are likely to break daily record low maximum temperatures for Halloween. Please see the CLIMATE section for more details. A clearing sky will greet the region late Thursday afternoon into the evening hours from west to east. A surface ridge will quickly slide southeastward across the area into the mid south and Ohio Valley. Southwesterly return flow around this surface ridge will act to help keep temperatures up a bit, with steadying or even slowly rising temperatures late Friday night for parts of the area. Consequently, raised low temperatures a few degrees for northwestern sections of the forecast area. That being said, very cold temperatures are still forecast areawide. Lows should range from the mid to upper 20s across the bi-state area. Gosselin .LONG TERM... (Friday through Next Wednesday) Issued at 336 PM CDT Wed Oct 30 2019 A broad long wave trof will dominate much of NOAM during this period. Short waves of varying intensity translating across the region within the mean long wave trof will be responsible for several frontal passages and any precipitation threat along with helping modulate temperatures. We are in between short waves on Friday in the wake of Thursday`s departing trof and just in advance of the next prominent trof. Low level WAA will be in full force in the wake of the retreating surface high pressure system and this along with an initial lack of clouds should allow for much warmer temperatures than Thursday`s chill. Still highs will remain below normal for the beginning of November. This upstream short wave trof will then amplify and dig into the Mississippi Valley Friday night into early Saturday driving a cold front through the region. The cold front itself will bring a reinforcing shot of cold air and keep temperatures well below normal. Any real question with this system is the potential for any post-frontal precipitation. The NAM is the sole model showing any potential into our CWA with the southern edge of a post-frontal band clipping northeast MO and west central IL between 06-12z Saturday. This band would be the result of low-mid level frontogenetic forcing and weak large scale forcing associated with the digging upper trof, and thermal profiles on the NAM would suggest largely snow. If this occurs it looks like a quick round with very minor accumulations less than an inch. The good news is that all of the other deterministic guidance and SREF and GEFS suggest this precipitation will remain north of the CWA, and that is the course of the current forecast. Otherwise brisk northwest winds and typical post-frontal stratus/stratocu is expected to accompany the front. Fast cyclonic upper flow accompanying the broad long wave trof will keep things zipping along and the surface high that moves into the region in the wake of the cold front moves quickly to the east on Sunday. This results in the return of low level WAA and moderating temperatures again Sunday-Monday, with highs approaching normal on Monday. Like yesterday we begin to see some differences with the deterministic model solutions and within members of the GEFS late Monday into midweek with the handling of short waves moving within the mean long wave trof. It still appears we will see a cold front move through the area Monday night into Tuesday. Whether or not it is accompanied by any precipitation depends on the amplitude of these aforementioned short waves and the resulting low level forcing. The ECMWF and GEFS mean are beginning to support a precipitation threat Tuesday into Tuesday night which should largely be rain at this point. Glass && .AVIATION... (For the 00z TAFs through 00z Thursday Evening) Issued at 650 PM CDT Wed Oct 30 2019 Band of wintry precipitation extending from eastern IA into eastern KS through northern MO, will gradually translate eastward tonight and Thursday morning, affecting all of the TAF sites with wintry precipitation types at some point as colder air spills in. This is expected to occur at KUIN around 02z and KCOU around 05z and involve a brief period of FZRA before becoming all SN. For the STL metro sites, this is expected to occur around 09z and should involve precipitation going straight to SN. This will intersect with the SN then tapering to flurries and ending during Thursday morning. The biggest runway impacts will likely be at KUIN where wintry precipitation will occur the longest but could also impact all the other TAF sites as well, becoming less likely towards the STL metro sites. Otherwise, look for IFR CIGs to persist for all TAF sites tonight and then clear out late Thursday morning or in the afternoon. N surface winds will back to NW and become gusty to 25-30kts later tonight and continue for much of Thursday. SPECIFICS FOR KSTL: Rain or drizzle will be the main precipitation-type until around 09z with a few hour window of potentially accumulating snow before it backs off to flurries by around 12z. FZRA probs during the transition looks too low to mention at this time. Otherwise, IFR conditions to prevail until Thursday morning with improvement to VFR and clearing during the afternoon. TES && .CLIMATE... Issued at 326 PM CDT Tue Oct 29 2019 Record low max temperatures for Thursday October 31st St. Louis 41 (1993) Columbia 39 (1993) Quincy 36 (1951) Record low temperatures on Friday November 1st St. Louis 26 (1954) Columbia 16 (1895) Quincy 23 (2014) && .LSX WATCHES/WARNINGS/ADVISORIES... MO...Freeze Warning from 1 AM to 10 AM CDT Thursday for Audrain MO- Boone MO-Callaway MO-Cole MO-Crawford MO-Franklin MO- Gasconade MO-Iron MO-Jefferson MO-Knox MO-Lewis MO-Lincoln MO-Madison MO-Marion MO-Moniteau MO-Monroe MO-Montgomery MO- Osage MO-Pike MO-Ralls MO-Reynolds MO-Saint Charles MO- Saint Francois MO-Saint Louis City MO-Saint Louis MO-Shelby MO-Warren MO-Washington MO. Freeze Watch from Thursday evening through Friday morning for Sainte Genevieve MO. Winter Weather Advisory until 10 AM CDT Thursday for Knox MO- Lewis MO-Shelby MO. Winter Weather Advisory until 10 AM CDT Thursday for Marion MO. IL...Freeze Warning from 1 AM to 10 AM CDT Thursday for Adams IL- Brown IL-Calhoun IL-Greene IL-Jersey IL-Macoupin IL-Madison IL-Monroe IL-Montgomery IL-Pike IL-Saint Clair IL. Freeze Watch from Thursday evening through Friday morning for Bond IL-Clinton IL-Fayette IL-Marion IL-Randolph IL- Washington IL. Winter Weather Advisory until 10 AM CDT Thursday for Adams IL- Brown IL. && $$ WFO LSX
Area Forecast Discussion
National Weather Service Marquette MI
857 PM EDT Wed Oct 30 2019 .SHORT TERM...(This evening through Thursday) Issued at 319 PM EDT WED OCT 30 2019 Confluent flow at jet level noted in RAP analysis and WV satellite from the eastern Dakotas and into the Upper Midwest. As would be expected under this confluent flow, MSAS analysis shows surface high pressure ridge extending ENE from the Rockies to the Upper Great Lakes. However, visible satellite shows the cirrus shield building in from the SW over the U.P. today in advance of a wave quickly ejecting out of the Rockies and across the Plains states today. This wave will spin up a surface cyclone tonight along the SW-NE oriented baroclinic zone stretching from the Southern Plains to Quebec. However with the parent long wave trough very positively tilted, this will be a progressive system and not be allowed to amplify enough to reach Upper Michigan with substantial precip. Previous NAM runs brought accumulating snowfall to the eastern ~1/3 of the CWA where no other major model did, but the 12z came in line with the other guidance in showing just the easternmost CWA (ISQ and ERY and points east) being grazed with very light snow tomorrow morning through afternoon. Regardless of what the NAM does or does not show, the basic idea of a progressive wave in a positively tilted long wave seems to argue for the less amplified solution that does not bring a surprise snow to any part the U.P., so feel comfortable keeping POPs and QPF very low. The result for this forecast is about half an inch of snow for ERY, ISQ, and MNM, and nada for points west of there from synoptic scale snow. For lows overnight tonight and highs tomorrow, stuck pretty close to the median of the distribution (and definitely did not bite on the MAV guidance that had a low of 8 at Watersmeet!). That ends up being mostly 20s tonight (maybe some upper teens interior west) and mid to upper 30s tomorrow. Now the interesting part. In addition to synoptically-forced precip, many of the CAMS today develop lake-effect bands/showers in NNW flow starting around sunrise tomorrow and continuing through the day. Moisture is progged to be very shallow with saturation only up to 4- 5 kft at best, so found it hard to believe any robust LES will develop even with 17-18 C delta T`s. Used the NNW LES primary edit area, filled it in with the HREF/SREF/CONSShort and such but then lowered them back down to 40 or less POP to account for the dry air aloft/shallowness of precip. For QPF did pretty much the same - initially used CAMS to highlight an area then backed down significantly. End result is again about a half inch of snow at most in eastern Marquette and western Alger County. But where it gets interesting is just how shallow the saturation is. It`s possible that some of this falls as freezing drizzle rather than as snow showers. Again, QPF amounts are very low and roads are still warm so not expecting any impacts, but wouldn`t be surprised if some windshields and other elevated surfaces get glazed tomorrow morning in Marquette and Alger Counties. For the rest of the Keweenaw and west, went with only flurries and sprinkles instead of snow showers/drizzle because of the shorter fetch length in an already extremely marginal setup. Regardless of any precip, there will plenty of lake-effect clouds around for almost all of the CWA, so it will be appropriately gloomy for Halloween. .LONG TERM...(Thursday night through Wednesday) Issued at 245 PM EDT WED OCT 30 2019 Upper air pattern will consist of a 500 mb closed low over the lower Great Lakes 00z Fri with more troughing in the Canadian and northern Rockies and northern plains. This last trough will dig southeast into the upper Great Lakes 00z Sat and this trough moves slowly across the area on Sat. Deeper moisture and 850-500 mb q-vector convergence moves in on Fri with the dynamics moving out Fri night into Sat, but the deep moisture remains. Did not make too many changes to the going forecast. In the extended, the GFS and ECMWF show a broad 500 mb trough over the ern half of the U.S. 12z Sun. This broad trough remains over the area into Wed. Looks active for this forecast period along with below normal temperatures. Nothing real big, just lots of little lake effect episodes. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 817 PM EDT WED OCT 30 2019 Lake-effect clouds continue at CMX with cigs MVFR the last few hours. Elsewhere, VFR conditions prevail early this evening. Expect MVFR cigs to develop at all sites late tonight or early Thursday morning as winds turn northerly and lake-effect clouds push in. Expecting it to be too dry for -SHSN at IWD and CMX (except for perhaps passing flurries). Could be on-and-off lake- effect -SHSN at SAW after about 12z, but even there it might end up being little more than flurries. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 319 PM EDT WED OCT 30 2019 N to NW winds 15-20 kts expected tonight and Thursday across the lake, with a brief increase to 25 kts possible east Thursday afternoon as a low pressure area tracks through the Lower Great Lakes. Winds become SW for Friday but stay at or below 20 kts. They then veer to NW Fri night as another trough approaches from the NW in Canada. As that trough passes over the lake, winds increase to 25- 30 kts Saturday. Winds become W and then SW behind the trough Sunday and relax below 20 kts Sunday into Monday. Next chance of 25+ kt winds after that is not until Tuesday afternoon. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...RJC LONG TERM...07 AVIATION...Voss MARINE...RJC