Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/15/21

Area Forecast Discussion
National Weather Service La Crosse WI
653 PM CDT Sun Mar 14 2021 .SHORT TERM...(This evening through Monday Night) Issued at 252 PM CDT Sun Mar 14 2021 The 14.12z models are even a bit slower with the movement of the snow into the area. The meso models are showing that the snow will move into northeast Iowa between 2 AM and 5 AM, southeast Minnesota and southwest Wisconsin between 5 AM and 8 AM, and west-central and central Wisconsin between 10 AM and 1 PM. One new development in the RAP and HRRR is that this band is weakening much faster and as a result the duration looks to be shorter for the highest hourly snow rates, so there is concern that the snow amounts might be trending lower. However, the 14.12z GFS did come in with higher snow amounts than it`s 14.06z run. Even though we are within 24 hours of the event, there continues to be a decent spread in the model snowfall amounts. Much of this has to due to with the precipitation amounts varying due to uncertainty on how fast the forcing will weaken, uncertainty on hourly rates, higher sun angle, compaction (from being a heavier, wet snow), dry air advecting in from east, and a warmer ground. The NBM 10th percentile has snow totals of up to 2 inches west of the Mississippi River and up to 1" south of Interstate 94 in western Wisconsin. Meanwhile, its 90th percentile is 4-7 inches west of the Mississippi River (highest in northeast Iowa) and 2-5 inches south of I-94 in western Wisconsin. Due to the spread, will trend the snow forecast toward the 25th to 75th percentile for snow amounts. The 14.12z HREF continues to show that the highest snow rates will be across northeast Iowa shortly after sunrise Monday. There is over an 80 percent probabilities of hourly snow rates between 7 AM and 9 AM but these probabilities decrease rapidly during the remainder of the morning. Elsewhere, snow rates will be up to a half inch per hour. However, there will be times that the hourly snow rates could be in the half to three-quarters of an inch. While the soundings continue to indicate that snow is the most favored precipitation type with this band. However, as the forcing weakens and we lose icing aloft, it still looks like the snow may change to light rain/freezing rain. This will be highly dependent upon on the surface temperatures and dew points. Due to the higher sun angle and less ground frost, there is some uncertainty in the day how much the icing from light freezing rain will occur on the roads. .LONG TERM...(Tuesday through Sunday) Issued at 252 PM CDT Sun Mar 14 2021 Main forecast concerns from Tuesday into Sunday are precipitation chances Wednesday into Thursday then temperatures Friday into Sunday. The 14.12z GFS/ECMWF/GEM are in decent agreement in slowly moving upper level closed low across the Central Plains States Tuesday night into Thursday. Forecast area at this time will be on the northern periphery of the upper level closed low. Southern half of the forecast area will see the highest chances of precipitation. As far as precipitation type...temperatures during the day will be above freezing and be all rain...then at night temperatures will be near or slightly below freezing and precipitation type will be all snow. Upper level closed low weakens and tracks into the eastern United States and upper level ridge amplifies over the central United States. The upper level ridge will allow for warmer air to advect into the region and 925mb temperatures are expected to warm to plus 6 to plus 9 degrees celsius by 00z Monday. High temperatures will rise into the 50s Friday through Sunday with the possibility of temperatures in the 60s at some locations Sunday. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 650 PM CDT Sun Mar 14 2021 VFR conditions through tonight will give way to MVFR/IFR on Monday as low pressure brings a round of winter weather. Snow is expected to begin at RST around 12-13Z, falling heaviest from late morning through mid-afternoon, then likely transitioning to light freezing drizzle late in the period. For LSE, snow should begin around 16-18Z but will not fall as intense as RST. LSE could see some drizzle mix in at times through the afternoon before a transition to light freezing drizzle just after the current period ends. Visibility at both sites will drop to IFR, perhaps LIFR at times at RST. Ceilings will drop to low end MVFR, perhaps IFR at RST. Winds will generally remain out of the east through the period. Gusts should briefly subside early this evening but will likely return overnight 20 to 30 knots as a low level jet drifts overhead. If gusts don`t materialize at the surface, expect a period of LLWS overnight. Otherwise gusts around 20 to 25 knots through the day Monday. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...Winter Weather Advisory from 7 AM to 7 PM CDT Monday for WIZ032- 033-041-053>055-061. MN...Winter Weather Advisory from 4 AM to 4 PM CDT Monday for MNZ086- 087-094-095. Winter Weather Advisory from 7 AM to 7 PM CDT Monday for MNZ079- 088-096. IA...Winter Weather Advisory from 4 AM to 4 PM CDT Monday for IAZ009- 010-019-029-030. Winter Storm Warning from 4 AM to 4 PM CDT Monday for IAZ008-018. Winter Weather Advisory from 7 AM to 7 PM CDT Monday for IAZ011. && $$ SHORT TERM...Boyne LONG TERM...DTJ AVIATION...Kurz
National Weather Service Hastings NE
657 PM CDT Sun Mar 14 2021 .DISCUSSION...(This evening through Sunday) Issued at 424 PM CDT Sun Mar 14 2021 Biggest concerns include severe weather potential through mid evening in our southern CWA as well as any ongoing minor flooding issues from the consistent rain that we have had over weekend. Later on into the night, attention turns to fog potential, especially north. Enhanced 50+ KT 925-850 mb are that were mixing down along with a very tight surface pressure gradient this morning giving 50+ mph wind gusts These enhanced elevated winds will continue to rotate north of the cold core low to the west and we will experience a noticeable decrease in wind speeds as the afternoon wears on. The overall precipitation shield will shift north as well, with folks in the far north being the last to see it go this evening. Perhaps a dusting of snow in our far north. Another focus for today will be areas of north central Kansas along the surface occlusion to the east of the surface low located in northwest Kansas. Hi-res models indicate the potential of some surface based CAPE this afternoon (conditional with breaks of clouds and sun allowing the surface to warm) with plenty of shear/deep layer shear in this vicinity. With the nearly stationary occluded front being a focus of increase storm relative helicity, and some moisture pooling occurring just north of the boundary with dewpoints perhaps getting to near 50 degrees this afternoon, all it would take is a little sun to help get convection going. The chance of a weak tornado is non-zero, so we will keep an eye out for this. Also, with such low freezing levels, some hail approaching severe limits would not be out of the question as well. Best chance for severe should remain west southwest of the CWA, however, closer to the surface low and closer to being underneath the cold core low aloft. We turn to fog potential tonight. With large quantities of rainfall recently and positive moisture flux within the east component to the wind tonight, the chance for reduced visibility is increasing. I have beefed up wording/grids significantly, and the HRRR surely backs this up. The upper level low will continue to give us additional rain chances and keep us on the cool side until we can finally get it out of here by mid-week, but unfortunately another trough moving through the southern/central Plains on Wednesday gives us yet another shot at some precipitation and perhaps a shot at a dusting of snow. We finally dry out by Thursday afternoon and beyond as upper level ridging works in and gives us a break with dry conditions and warmer weather. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Tuesday) Issued at 651 PM CDT Sun Mar 14 2021 We are expecting pretty poor aviation weather conditions the next 24 hours with the biggest problems being the low clouds and possible fog. Confidence is not real great on the fog, but confidence is high that we will see at least IFR or LIFR ceiling conditions through most of the TAF valid period. Most of the rain has ended, but we can`t rule out a few passing showers. The most likely time frame for the fog will be from late evening through 3 or 4 hours after sunrise. && .GID WATCHES/WARNINGS/ADVISORIES... NE...NONE. KS...NONE. && $$ DISCUSSION...Heinlein AVIATION...Wesely
Area Forecast Discussion
National Weather Service Lincoln IL
801 PM CDT Sun Mar 14 2021 .SYNOPSIS... Issued at 307 PM CDT Sun Mar 14 2021 Scattered very light rain showers will continue across central Illinois this evening, before a band of heavier rain arrives late tonight into Monday morning. The atmosphere will become cold enough to support a mix of freezing rain and sleet along and north of I-74. However, little or no ice accumulation is expected. && .UPDATE... Issued at 802 PM CDT Sun Mar 14 2021 Impressive dew point gradient noted just south of I-74 early this evening, with teens/20s north of it and 35-40 from I-72 south. This has done a number on the northeast movement of the rain, with our evening balloon sounding showing the dry layer about 8,000 feet thick. Upstream dew points across northern Indiana are as low as 10-15 degrees, but as winds in our area develop more of an easterly component late this evening, the precip should start to make some decent eastward progress. Precip type should mainly remain rain through the night, but a mix with some sleet and perhaps freezing rain will be possible from I-74 north by sunrise. Main concern for mixed precip will be in the 7-11 am time frame on Monday, with NBM showing >90% chance of sleet along the I-74 corridor and accumulations potentially a half inch or more. Signal on the forecast soundings continues to be favorable for some freezing rain in this area as well, but 4 inch soil temperatures are currently in the 40-45 degree range, so any accumulations would likely be more on elevated surfaces and not last long with temperatures rising into the mid 30s. && .SHORT TERM...(This evening through Monday) ISSUED AT 307 PM CDT Sun Mar 14 2021 19z/2pm water vapor imagery shows a deep upper low spinning over eastern Colorado, with downstream short-wave ridging across the Midwest. Despite the ridging, weak mid-level forcing has triggered bands of very light rain showers across the KILX CWA this afternoon. Latest radar trends suggest the bands will remain south of I-74 and will eventually erode due to dry advection from the northeast. HRRR and other CAMs indicate the initial band will dissipate over the next couple of hours: however, a second band will likely form across the same area later this evening. Any precipitation that occurs this afternoon and evening will be quite light, only amounting to a couple hundredths of an inch at best. The stronger forcing associated with the Colorado low will slowly pivot into the region overnight, resulting in a heavier band of precip spreading into central Illinois from the southwest toward dawn. Model timing has been very consistent...showing rain increasing along/southwest of a Macomb to Taylorville line between 06z/1am and 09z/4am...then spreading across the remainder of the area shortly after daybreak. While most of central Illinois will see rain, locations along/north of I-74 will cool sufficiently to support a period of sleet and perhaps freezing rain late tonight into Monday morning. While surface temps will drop into the lower to middle 30s across this area, the ground is no longer frozen, so any freezing rain that occurs will produce little in the way of icing. May see a light accumulation of sleet across the north before the precip band quickly lifts E/NE of the area toward midday. Once the band departs, Monday afternoon will be overcast and largely dry with high temperatures ranging from the upper 30s north of I-74 to around 50 degrees south of I-70. .LONG TERM...(Monday night through Sunday) ISSUED AT 307 PM CDT Sun Mar 14 2021 As the Colorado low slowly tracks into Illinois, showers will re-develop Monday evening. In fact, NAM/GFS MUCAPE values of 200-500J/kg suggest the potential for a few rumbles of thunder as well. Have bumped PoPs to likely across much of the CWA and mentioned a slight chance of thunder accordingly. After the low exits, mild and dry weather will be on tap for Tuesday before another storm system comes into the picture by the middle of the week. Models tend to track this particular system just to the south from the Southern Plains into the Ohio River Valley Wednesday through Friday, keeping central Illinois on the cool side of things. Have introduced PoPs as early as Wednesday morning, but based on the highly amplified nature of the upper wave, think the primary focus for rain will be Wednesday night into Thursday. After that, dry weather will return for next weekend. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 618 PM CDT Sun Mar 14 2021 Main issue in the short term will be with east winds increasing this evening, as gusts approach 30 knots before 05Z and may be as high as 35 knots between 09-14Z. A strong low level around 2,000 feet will help to amplify these gusts, and a mention of LLWS continues. Steadier rain should begin moving in after 06Z, and ceilings and visibilities will deteriorate overnight and past 12Z. A rain/sleet mix will be possible near KPIA/KBMI between 12-16Z. As the rain moves out around midday and winds diminish a bit, ceilings are expected to lower to below 1,000 feet for the afternoon. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Geelhart SYNOPSIS...Barnes SHORT TERM...Barnes LONG TERM...Barnes AVIATION...Geelhart
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
928 PM CDT Sun Mar 14 2021 .UPDATE... 928 PM...Evening update...No changes for tonight or Monday. Some of the recent HRRR/RAP runs are changing the precipitation over to snow faster on Monday and as a result have some higher snow totals across the western and northwestern parts of the area. Latest 00z NAM is coming in and generally in-line with our current forecast. While some locally higher snowfall amounts are possible, will hand off that potential to the incoming mid shift with review of the entire 00z suite of guidance. Current two segment SPS remains in effect until 08z and covers the current expected amounts and impacts well. cms && .SHORT TERM... 339 PM CDT Through Monday night... We may be in meteorological spring, but winter is not quite done with us yet! We had been spared from any wintry precipitation so far this month, but as is always the case in the month of March, we will not escape this month snow-free due to a deep low pressure system currently sitting over eastern Colorado. National radar mosaic nicely depicts an expansive precipitation footprint associated with this low stretching from the Rockies to the Appalachians with a swath of rain also extending down southward to the Texas Coast along a healthy moist conveyor belt. The northernmost flank of precipitation sits draped across central Illinois this afternoon, just south of our forecast area, which remains firmly rooted in a very dry air mass. There is a chance that some of the light rain farther downstate creeps into the far southern part of the CWA later today, but with the dry air mass still in place, any of this would likely remain as virga. The upper low will pick up its pace later tonight as a longwave trough digs towards the southwestern U.S. and nudges the low northeastward. An east-southeasterly low-level jet currently stretching from northern Missouri into eastern Nebraska will move over our south overnight with roughly 50 kt flow progged at 925 mb (~2000 km AGL) between about 9 and 15Z. Guidance remains mixed on the degree of boundary layer decoupling overnight and thus the extent to which we may be able to tap into this jet. Think guidance like the HRRR and the RAP may be a little too aggressive with the mixing of ~50 mph gusts to the surface south of I-80 tomorrow morning, but nevertheless, it should still be a fairly blustery morning with the tight surface pressure gradient across the region. As has been alluded to in previous discussions, the low will have a lot of work to do to saturate the bone dry air mass that is currently in place. While these saturation efforts are already underway to some extent, they will be mostly futile for the time being with a broad area of high pressure tracking southeastward across Ontario providing a healthy replenishment of dry air into the region to offset any moistening. As the low tracks closer, the combination of moist advection, isentropic ascent, and dynamic cooling induced by lift provided by favorable jet dynamics will eventually achieve its goal of saturating the column sufficiently for precipitation to start reaching the ground, but that likely won`t happen until tomorrow morning for our southern and western counties and possibly not until early tomorrow afternoon farther northeast. It`s entirely possible, if not likely, that at least part of the Chicago metro stays dry the entire morning, especially as you head farther north. The precipitation type forecast remains challenging and convoluted even as we are within 24 hours of the event now, and our forecast grids reflect that as they seem to resemble a child`s finger painting with all of the various colors representing different precipitation types and mixes splattered across the area. This is primarily due to the combination of the presence of a 850-700 mb warm (above freezing) nose, which will melt some amount of snow aloft; sub-700 mb temperature profiles generally hugging the freezing line, meaning that even a 1-2F degree difference somewhere in the temperature profile could swing precipitation type from one mode to another; and the continuing feed of dry air that will keep wet-bulb temperature profiles mainly below freezing in the lower levels, allowing for evaporative cooling to offset much of the ongoing low-level warm air advection. That being said, based on our current forecast, the general precipitation type evolution looks to feature a wintry mix including sleet and possibly freezing rain across the southern two-thirds of the forecast area during the morning and early afternoon with the main bout of precipitation likely ending as rain or a rain/snow mix by late afternoon. Across our northern counties, we look to have a more homogeneous precip type forecast of mainly snow during the morning and early afternoon. Although, it is likely that some other precip types will at least briefly mix in somewhere here before most of the precipitation ends (a rain/snow mix seems to be the favored solution, but a mix including sleet is not entirely out of the question either). Moderate to briefly heavy precipitation rates would be favored to occur shortly after precipitation onset and will generally diminish as the precip shield marches northeastward with time as the upper low starts shearing out more and the associated sources of lift weaken. The majority of any precipitation looks to end by the early evening as a mid-level dry slot slides through the area, but some patches of drizzle and/or snizzle could hang around into the overnight hours. Additionally, as the occluded surface low tracks across central Illinois, a wave tracking overhead should induce a more concentrated area of rain showers across mainly the southern half of the forecast area Monday night, although some of this activity will likely sneak into the Chicago metro. Some of these showers would be convectively-driven, and it`s not entirely out of the realm of possibility that we get an isolated lightning strike or two somewhere in the forecast area. All precipitation should be out of the area by daybreak Tuesday. The going precipitation accumulation forecasts of up to 0.5" of sleet, up to 0.1" of ice accumulation generally south of I-80, and 1- 3" of very wet 5:1 to 8:1 SLR snow generally north of I-80 (highest accumulations towards the Rockford metro and northwest Illinois where better forcing with the right entrance region of an easterly upper jet streak will be present) with 1" or less generally south of I-80 seem adequate. However, with surface temperatures expected to mainly be at or above freezing by the afternoon, any ice accumulations from freezing rain would likely not last long, and the wet snow may have difficulty accumulating on relatively warm roadways, which should limit the overall impacts that we see with this system. We opted to not issue any Winter Weather Advisories for both this reason and because of the persisting uncertainty with exact precipitation types and rates. Nevertheless, the potential for slushy snow accumulations on colder roadways and the brief potential for freezing rain to impact travel will be messaged via SPSs and graphics. Lastly, easterly winds gusting to around 35 mph out over Lake Michigan will lead to the potential for minor lakeshore flooding along the Illinois lakeshore. With the lake levels trending downwards over the past few months and only a marginal wind and wave forecast for lakeshore flooding potential, have opted to continue holding off on any Lakeshore Flood Advisory issuance. Ogorek && .LONG TERM... 302 PM CDT Tuesday through Sunday... The main focus during the long term period will be the next potential precipitation and wind maker for the area Wednesday night and Thursday. Otherwise, relatively quiet weather is anticipated. Low-level cloud cover is likely to linger across much of the area into Tuesday, but dry weather is expected. Seasonal high temperatures are forecast for inland areas on Tuesday, with readings generally in the 40s. Cooler conditions are expected along the shores of Lake Michigan due to continued onshore flow. Slightly warmer temperatures are forecast for Wednesday as we await the approach of our next storm system taking shape over the southern Plains. Similar to Tuesdays weather, the coolest temperatures (lower 40s) will be near the lake, with inland areas likely to climb to around 50. Forecast guidance continues to merge towards a slower solution with the Wednesday night and Thursday storm system. Basically this means much of the daylight hours of Wednesday will likely end up precipitation free across the area. Rain then looks to develop northeastward over the area Wednesday night and continue on Thursday as the center of the storm system tracks eastward across the central Mississippi Valley towards the Ohio Valley. Thermal profiles across the area from non-GFS guidance all continue to favor all rain, but its possible some wet snowflakes could mix in along the northwestern periphery of the precipitation shield late Thursday. Northeasterly winds are expected to become gusty with this system on Thursday, and this does add some concern for the possibility of lakeshore flooding. Overall, the surface gradient along the northern periphery of the surface low should become favorable for some stronger north-northeasterly winds down the lake due to the presence of a fairly stout area of high pressure to the north over western Ontario. Wind gusts of 35 to 40 mph are certainly possible with such a setup, and the onshore component adds some concern for large waves and an associated water level surge occurring across the southern shores of the lake. For this reason, we will to keep an eye on the possibility for at least minor lakeshore flooding with this storm system. Quiet weather returns to the area from Friday and into next weekend as a large surface high shifts southeastward across the Great Lakes. Temperatures in this pattern should moderate from around 50 on Friday to potentially up around 60 by Sunday. However, cooler temperatures are likely near the lake for Friday and Saturday due to continued onshore flow. KJB && .AVIATION... For the 00Z TAFs... Forecast Concerns: * Messy wintry system Monday (SN,PL,FZRA,RA) and associated IFR conditions * Potential for LIFR/VLIFR vis under any heavier snow bands * Gusty ENE/E winds through the period The Central Plains closed low will approach the area Monday morning with precipitation expected to arrive at the terminals mid to late morning. Latest guidance has trended a little bit earlier with the onset of the heaviest precipitation and have adjusted the timing of the TEMPO groups accordingly, but suspect the previous concerns with the impact of dry air out ahead of the precip shield remain a factor. A wintry mix of precipitation is expected, ranging from mostly snow and some sleet out toward RFD, and more of a mix of PL and SN at the Chicago area terminals. Precipitation type and timing will continue to be refined as we get closer to the event. If snow becomes the more predominant precip type for a period, the steep lapse rates would support visibility reductions potentially nearing LIFR to even VLIFR. Have maintained IFR vis and cigs for now due to lower confidence. As the primary band of precipitation lifts to the northeast a mix of light rain/drizzle and a few flurries will remain possible into the evening hours. Winds remain gusty into this evening before easing slightly tonight. Heading into early Monday morning, expect gusts to ramp back up into the upper 20 kt range ahead of the approaching system. A few higher gusts into the lower 30kt range are certainly possible with a strong low-level jet overhead. Surface winds remain elevated enough to preclude a formal low-level wind shear (LLWS) mention. Gusts then remain elevated through the TAF period but begin to ease with the passing of the band of precip. Petr && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...Small Craft Advisory...IL nearshore waters until 4 AM Tuesday. Small Craft Advisory...IN nearshore waters until 10 PM Monday. && $$ Visit us at Follow us on Facebook, Twitter, and YouTube at:
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
926 PM CDT Sun Mar 14 2021 .UPDATE... Issued at 922 PM CDT Sun Mar 14 2021 The current forecast is on target with a wet and windy night on tap. Since late afternoon we have been seeing periodic west-east oriented bands of light rain across central/eastern MO into west central IL. These northward moving bands are associated with low- level WAA and moisture convergence and low-mid level frontogenetic forcing. Later this evening/overnight the more prominent NW-SE arcing band of rain associated with synoptic scale forcing and the warm conveyor belt will translate eastward across the CWA, attendant with the slow eastward migration of the large extratropical cyclone into the Plains. Weak elevated CAPE (< 200 j/kg) is progged across southeast MO as the band moves eastward overnight, so a rumble or two of thunder remains possible. Otherwise the band should produce an additional 0.50-1.00 inch of rain, by the time it exits in the 15-16z time frame. A rather tight surface pressure gradient resulting from the Plains cyclone and surface high in the Great Lakes region will continue to generate impressive easterly winds, gusting as high as 40 mph or so the remainder of the evening and overnight. We are still closely watching the potential for some vigorous thunderstorms between 21-01z across parts of central MO, and maybe east central MO, in the vicinity of the occluded front/warm front. The RAP is suggesting the combination of heating after skies clear in the afternoon and steep lapse rates aloft could result in MLCAPE approaching 500 J/KG. This in combination with strong deep layer shear could result in some organized low-topped storms. Low freezing levels and low wet bulb zero heights would suggest hail would be the primary threat. Glass && .SHORT TERM... (Through Late Monday Night) Issued at 249 PM CDT Sun Mar 14 2021 Currently, an upper-level low is slowly moving through the Plains, and its associated surface low can be seen on visible satellite spinning across eastern Colorado and western Kansas. Over the Middle Mississippi Valley, a band of light rain associated with an area frontogenesis is currently on the northeastern edge of the CWA and is expected to continue drifting northward and weaken. The remainder of the afternoon into the early evening will remain cloudy with a chance of isolated showers thanks to low-level warm air advection ahead of the approaching surface low. The leading edge of the main swath of rain associated with the low is currently pushing into western Missouri, and is expected to push eastward into the CWA this evening. This rain will transition through the area rather quickly this evening and overnight, limiting the flooding potential. Rainfall totals by tomorrow morning when the rain ends will top out around 0.50-0.75" area wide. Instability will be limited with this rain, but there may be enough across far southeastern Missouri and far southern Illinois to produce a rumble of thunder or two overnight. An item of concern is the low-level jet this evening into early tomorrow morning. Guidance has a narrow swath of ~50 kt easterly/southeasterly winds at 925 mb primarily over northeastern Missouri this evening drifting into western Illinois during the morning. If these winds are able to overcome the stable layer and mix down to the surface, they may produce gusts of 40+ mph primarily north of the I-70 corridor. If this were to happen, it would most likely occur in pockets of heavier rainfall and be sporadic and short lived. Confidence is higher in gusts topping out in the 30-40 mph range overnight into the morning over this portion of the CWA. The band of rain will depart the CWA to the east tomorrow morning, providing a brief lull in precipitation chances. An occluded front will stall along the I-70 corridor, and the weakening surface low will track along it through the day. Upper-level divergence and weak differential vorticity advection from the upper-level low pivoting northward over the Middle Mississippi Valley will spark showers along and north of the front during the afternoon and evening, and guidance depicts a couple hundred J/kg of MUCAPE across the CWA with this activity. With steep lapse rates in place, I can`t rule a low- top thunderstorm or accompanying the showers. These storms may be capable of producing small hail thanks to the freezing level hovering around 800 mb and 0-6 km bulk shear of at least 50 kts. The rain/storm chances will diminish through the evening. Elmore .LONG TERM... (Tuesday through Next Sunday) Issued at 249 PM CDT Sun Mar 14 2021 On Tuesday, the upper-level low over the Midwest will be in the process of decaying and becoming sheared apart as another upper- level low moves out of the Desert Southwest and into the Southern Plains. Upper-level flow over the Middle Mississippi Valley will initially be zonal, but slowly transition to southwesterly through the day. Low-level flow will follow suit, and begin advecting warm, moist Gulf air over the CWA later on Tuesday ahead of the previously mentioned upper-level low moving into the Plains. The surface low associated with this feature is set to develop over the Southern Plains and track northeastward toward the Middle Mississippi Valley. While the consensus among ensemble guidance is that the CWA will see another round of rain starting late Tuesday night into Thursday with this system, there is still much spread on the speed and track of the low. This has implications on storm potential, where a more northerly low track would put at least the southern portion of the CWA in the warm sector with a heightened shear and instability parameter space. With this scenario, a severe weather threat would be possible, and this is supported by the CIPS Severe Probability Guidance, which has had placed a heightened probability of severe weather across southeastern Missouri and southwest Illinois over the last several runs. A more southerly track would keep the warm sector south of the CWA and mitigate the threat. The spread among guidance does not give me enough confidence to say which scenario is more likely at the moment, and we`ll need to watch this closely in the upcoming days. The chance of rain diminishes through the day on Thursday as the surface low continues eastward. In its wake, flow through the atmosphere over the Middle Mississippi Valley will be northerly/northwesterly, advecting cooler air into the CWA and keeping temperatures 5-10 degrees below normal through the end of the week. Temperatures will begin to rise as we enter the weekend in response to upper level ridging building into the Middle Mississippi Valley. Elmore && .AVIATION... (For the 00z TAFs through 00z Monday Evening) Issued at 638 PM CDT Sun Mar 14 2021 Strong and gusty east winds will persist much of the night. These strong winds increase rather uniformly with height through the lowest 3000 feet AGL. Otherwise intermittent light rain is expected to impact the terminals this evening, especially KCOU and KUIN. Flight conditions at KCOU are expected to be predominately MVFR, and VFR at the other terminals. A more solid and continuous band of rain will then move west to east across the region overnight, impacting all the terminals and accompanied by deteriorating flight conditions, both cigs and visibilities. The rain should have exited the area by 14z however IFR flight conditions are expected to persist in it`s wake. By midday flight conditions are expected to improve with KCOU and the St. Louis metro terminals VFR by early afternoon. Scattered thunderstorms will be possible after 21z in middle MO hence the inclusion of VCTS at KCOU. SPECIFICS FOR KSTL: Strong and gusty east winds will persist much of the night. These strong winds increase rather uniformly with height through the lowest 3000 feet AGL. Intermittent light rain is expected to impact KSTL this evening with flight conditions remaining VFR. A more solid and continuous band of rain will then move into the terminal overnight accompanied by deteriorating flight conditions, both cigs and visibilities. The rain should have exited by 14z however IFR flight conditions are expected to persist in it`s wake. Flight conditions will improve by midday with VFR by early afternoon. Glass && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX
Area Forecast Discussion
National Weather Service Pueblo CO
929 PM MDT Sun Mar 14 2021 .UPDATE... Issued at 919 PM MDT Sun Mar 14 2021 Will be ending Winter Storm Warnings for the Sangres/Wets and srn El Paso County with this update, and taking down the advisory for the San Juans/La Garitas as well. Will hold on to warnings for the central mountains for at least a couple more hrs, and will likely keep nrn El Paso and Teller county warnings going through midnight as combination of light snow and blowing/drifting snow will keep will visibility low for a few more hrs. UPDATE Issued at 548 PM MDT Sun Mar 14 2021 Ended winter storm warnings for the Arkansas Valley from Canon City up through Salida and Buena Vista, as obs and radar show only a few snow showers these areas, and latest HRRR has only very light precip for the remainder of the night. Will leave mountain highlights up a couple more hrs, though suspect all but Teller and nrn El Paso County can be dropped at some point this evening. && .SHORT TERM...(This evening through Monday) Issued at 316 PM MDT Sun Mar 14 2021 ...Blizzard Conditions Continue for Northern El Paso County through Midnight... Upper low continues to spin over eastern CO with upper low center around 20 miles northwest of Lamar. Moderate to heavy precipitation/snow continues within the TROWAL region wrapping around the west side of the upper low across the I-25 corridor and adjacent plains. There are embedded convective elements across the southeast plains along its eastern edge extending towards the upper low center. Heaviest snow continues to fall across El Paso county where temperatures have been sufficiently cold for an all snow precipitation type. And strong northerly winds around the back side of the system has pulled 45 kt wind gusts down to the surface along across northern El Paso county southward through Pueblo county and eastern portions of Huerfano and Las Animas counties. This has resulted in blizzard conditions for northern El Paso county where winds and snow have caused visibilities to drop to 1/4 mile or less. Seeing 12 to 18 inch snowfall reports so far across northern El Paso county and northern Teller Counties. With wrap around precipitation expected to continue for a few more hours some areas could see an additional 2-6 inches before the storm pulls east and snowfall diminishes around midnight. Current headlines will come down from 06z and 12z. Considered changing the ending time to midnight for the southeast mountains and eastern San Juans but given the persistence of some snow bands around western side of upper low which have not been resolved well by some high res models, decided to leave highlights as is and later shifts can end them sooner if need be. Winds also decrease across the plains after midnight so ending time of midnight for the Blizzard warning still looks on track as well. Also watching some intense snow bands across the southern I-25 corridor this afternoon as well. So far impacts to roads have been minimal with day time warmth keeping roads just wet, but visibility has been low at times. Also watching some embedded convection across the far southeast plains this evening. So far have seem some CAPE up to 200 J/kg with most of the lightning just clipping by northeast Kiowa county. As temperatures cool this evening, could see an inch or two of snowfall across Kiowa county as the wrap around precipitation pulls eastward into this area. Given the warm road temperatures, do not think advisories will be needed but this area will be monitored closely. Southern Colorado will be in between systems on Monday as potent storm system pulls away to the east and the next makes its way through southern CA. Have cooled down high temperatures over snow pack areas but all other areas should see a rebound in temperatures and a day of melting. -KT .LONG TERM...(Monday night through Sunday) Issued at 316 PM MDT Sun Mar 14 2021 The operational models are in decent agreement through the extended with the next upper system impacting the area early this week, followed by drier weather mid to late week. Ensemble spreads are overall low, with modest confidence through the extended period. Monday night...upper level shortwave ridging will be transiting the region during the overnight hours ahead of the next upper storm system. For much of the overnight period, it will remain dry. A few snow showers will likely move into the Continental Divide late and increase in coverage by Tuesday morning. Overnight lows will range for the teens over the San Luis Valley, to 20s across the Plains. Tuesday into Wednesday...a quick moving upper level low is forecast to move across the Desert Southwest and into Oklahoma during this period. Given the current projected storm track across New Mexico, a cold front will back west across the Plains on Tuesday, with upslope flow wrapping around the system through 700 mb. This will lead to another round of snowfall for the Eastern Mountains, south into the Raton Mesa region from Tuesday afternoon through Wednesday morning. Snow amounts remain in question with the onset looking like rain for the lower elevations. As we cool Tuesday night into Wednesday, any rain should transition to snow, before coming to an end Wednesday afternoon as the system quickly ejects into Oklahoma. Mountain locations over the San Juans, Southern Sangre de Cristo and Wet Mountains could see 3 to 7 inches, with locally higher amounts possible. For the lower elevations including the southern I-25 corridor, 1 to 4 inches may be possible, especially if this area transitions to snow. For the rest of the area, an inch or two may be possible late Tuesday night and Wednesday morning. Much will depend on the exact storm track as slight shifts could mean more or less snowfall. It is also a very quick moving system, which will likely limit snowfall potential to expected totals listed above. Temperatures will be on the cooler side both Tuesday and Wednesday, with 40s across the lower elevations. Thursday through Saturday...upper level high pressure will slowly shift east across the state with dry conditions expected. Temperatures will also warm from the 50s on Thursday, to near 70 on Saturday. As the upper system shifts east, flow aloft will transition southwesterly. Breezy conditions are possible on Saturday across the Plains. Southwesterly flow will also favor a few snow showers along the Continental Divide by the weekend. Sunday...the next upper trough will begin to impact the region by next Sunday. Snow will likely increase along the Continental Divide, and spread eastward to the Plains by late in the day. Given that this is a week out, much is subject to change with this storm system. Mozley && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 316 PM MDT Sun Mar 14 2021 IFR to LIFR conditions will continue at KCOS for a couple more hours before the snow pulls back to northern El Paso county and cigs and vis improve. KPUB will remain VFR with brief drops into the MVFR category with -SHRA/-SN. Winds will gust to around 45 kts through around 03z before decreasing at both KCOS and KPUB though gusts to around 25 to 30 kts will be possible through much of the night. Should see clearing skies Monday morning with VFR conditions and winds becoming light and diurnally driven in the afternoon for both terminals. KALS will still see a chance for -SHSN for a couple hours this evening before skies clear out towards morning. Winds will become light southerly with speeds under 15 kts for KALS Monday afternoon. -KT && .PUB WATCHES/WARNINGS/ADVISORIES... Blizzard Warning until midnight MDT tonight for COZ084. Winter Storm Warning until 6 AM MDT Monday for COZ058>061-063- 081-082. && $$ UPDATE...PETERSEN SHORT TERM...KT LONG TERM...MOZLEY AVIATION...KT