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Tim from Springfield (IL)

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  1. Tim from Springfield (IL)

    Sept. 2-4 Severe Threat

    Looks like Lake Michigan had a "hurricane" of their own. A waterspout near Beach Park, IL this evening. Courtesy of a poster on the Northern IL Severe weather FB group:
  2. Tim from Springfield (IL)

    Sept. 2-4 Severe Threat

    5/15/15 probs (5% TOR) on the 1AM Day 1. Still SLIGHT. Higher probs possible later in lower MI: https://www.spc.noaa.gov/products/outlook/day1otlk.html ...Midwest into the Great Lakes and Mid MS Valley... A long-lived MCS over far southeastern MN and western/central WI early this morning will likely continue southeastward across WI for at least the next several hours along an instability gradient. This line of storms should continue to gradually weaken with southeastward extent this morning as it encounters a less unstable airmass. However, strong low/mid-level flow associated with a shortwave trough over the northern Plains may allow these storms to persist for longer than most model guidance suggests. An isolated hail/wind threat may be ongoing at the start of the period across parts of northern IL and vicinity if these storms can maintain their intensity, especially on the southwestern flank of the line where instability is relatively greater. The convective scenario for today remains rather uncertain given the potential for this morning MCS to delay/disrupt diurnal destabilization, particularly with northward extent into Lower MI. A relatively greater chance for moderate to strong instability to develop may occur along a trailing outflow boundary from these morning storms across parts of northern IL/IN into far southern Lower MI. Strong large-scale forcing for ascent attendant to a southeastward-moving shortwave trough will overspread these areas by this afternoon. Additional convective development appears likely along or just ahead of a surface cold front by peak afternoon heating. The presence of a 50-70+ kt mid-level westerly jet will support strong effective bulk shear values over this region. Any storms that can form in this environment will likely become organized and pose an isolated large hail and damaging wind threat. Initially semi-discrete storms will probably grow upscale fairly quickly along the cold front or remnant outflow boundary, with a damaging wind threat potentially continuing into the evening across parts of central IL/IN and northwestern OH. The degree of the tornado threat will be dependent on storm mode, but a southwesterly low-level jet will overspread much of the warm sector through the afternoon. Isolated tornadoes will be possible given the strong low-level shear that will be present. Greater severe probabilities may be needed across some part of the Midwest into southern Lower MI, but too much uncertainty exists regarding morning storms to introduce them at them at this time.
  3. Tim from Springfield (IL)

    Sept. 2-4 Severe Threat

    If the current Day 2 hatched area, which includes Chicago and Detroit, gets cranked up--and tornadic--I wonder WWTWCD. If they will have to interrupt Hurricane Dorian wall-to-wall coverage with Dr. Greg Forbes.
  4. Tim from Springfield (IL)

    Sept. 2-4 Severe Threat

    Day 2 includes slight for SE WI, and most of the N half of IL and Southern Lower MI, as well as N IN and NW OH: https://www.spc.noaa.gov/products/outlook/day2otlk.html ...Great Lakes... Models are in good agreement in a scenario with morning storms over the western Great Lakes in association with a strong southwesterly LLJ. A lingering severe risk may accompany this activity mainly in the form of isolated damaging gusts before dissipating by the late morning. A plume of steep 700-500mb lapse rates will advect northeast into the southern Great Lakes during the day. Despite a capping inversion, convergence near the boundary and strong heating will likely lead to local erosion of the cap and isolated to scattered storm development by late afternoon from northern IL east into southern Lower MI. A moderate to very unstable airmass is progged by guidance with 3000+ J/kg MLCAPE possible across IL and decreasing to 1500 J/kg into Lower MI. Hodographs are forecast to enlarge during the late afternoon/evening across the southern Great Lakes concurrent with diurnal storm development. A mix mode of supercells and multicells capable of all severe hazards are possible primarily during the 21z-03z period. Farther southwest over MO into western IL, lower storm coverage is forecast but large CAPE and a wind profile supportive of organized storms would lend a conditional risk for severe with the stronger storms.
  5. Tim from Springfield (IL)

    Sept. 2-4 Severe Threat

    ENH risk for severe on this Labor Day from eastern ND to W WI, with slight including most of the northern half of WI: https://www.spc.noaa.gov/products/outlook/day1otlk.html ...Northern Plains through upper Mississippi Valley... A shortwave trough will amplify as it moves east southeast through southern Alberta and Saskatchewan, reaching the northern Plains by early this evening and the upper MS Valley late tonight. Downstream from this feature, a warm front will advance northeast, and will be situated from a weak surface low in northwest ND through northeast SD and central IA by early evening. A cold front will extend southward from the low through the western Dakotas and advance east during the evening. A moist warm sector will reside south of the warm front. Surface dewpoints will range from the mid 60s to upper 70s F beneath a plume of steep mid-level lapse rates associated with the eastward expansion of an elevated mixed layer (EML). Warm air at the base of the EML will result in a substantial cap in warm sector during the day. Theta-e advection along a southerly low-level jet will contribute to northeastward destabilization through the Dakotas and into the upper MS Valley this afternoon and evening with MUCAPE increasing from 2000-3000 J/kg north of the warm front. Isolated storms with a marginal hail threat may be ongoing from SD into NE within zone of warm advection. However, primary severe threat is expected during the afternoon into the evening when forcing for ascent associated with approaching shortwave trough and attendant strengthening low-level jet will result in development of storms north of the warm front over northern ND. These storms will be elevated, but effective bulk shear from 40-50 kt and a favorable thermodynamic environment will support a few supercells with large hail the initial primary threat. Storms may eventually evolve into an MCS with primary threat transitioning to damaging wind during the evening and overnight as activity continues southeast through MN into WI along instability gradient. Given favorable low-level hodographs, a conditional threat will exist for a couple of tornadoes with any surface-based storms that can develop on the warm front. However, current indications are that the warm sector will probably remain capped to parcels originating in the boundary layer.
  6. Tim from Springfield (IL)

    September 2019 General Discussion

    Heavy rains and flash flooding from IMO freak thunderstorms in the SPI area from roughly 2-7AM Sunday morning. Chatham, just southwest of Springfield may have had upwards of at least 7 inches of rain. https://www.sj-r.com/news/20190901/storms-sock-springfield-area-early-sunday-morning
  7. Tim from Springfield (IL)

    Severe/Heavy Rain possibilities 8/16-8/18/19

    Watch possible for SE MO, S IL, and central IN: https://www.spc.noaa.gov/products/md/md1791.html
  8. Tim from Springfield (IL)

    Severe/Heavy Rain possibilities 8/16-8/18/19

    New D1 outlook has Slight across most of southern IL, but the main focus will be outside the sub in C/W MO and E KS, where there's a hatched for hail: https://www.spc.noaa.gov/products/outlook/day1otlk.html Tomorrow's D2 has a Slight reaching western IL: https://www.spc.noaa.gov/products/outlook/day2otlk.html Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Fri Aug 16 2019 Valid 171200Z - 181200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM SOUTH DAKOTA...NEBRASKA AND KANSAS EASTWARD INTO WESTERN ILLINOIS.. [ . . . ] ...Dakotas and northern NE into IA and IL... Substantial height falls will occur over the Dakotas during the day with increasing deep-layer shear. Storms will form relatively early along the cold front over the western Dakotas, and will increase in intensity as they encounter a destabilizing air mass to the east. Damaging winds and hail will be possible. Models suggest storms will make it into western MN by late evening, but likely weaker. ...KS into MO... Storms are forecast to be ongoing from eastern KS into MO Saturday morning, possibly in the form of an MCS on the nose of the low-level jet. Damaging winds will be possible initially, but a weakening trend is expected after about 18Z. Behind this initial activity, strong heating of a moist air mass, beneath cool temperatures aloft will lead to strong to perhaps extreme instability, with MLCAPE values in excess of 3500-4000 J/kg over parts of KS, northwest MO, and into NE. There is spread between the models regarding where afternoon and evening convection will initiate, and this may depend on modifying outflow boundaries. At this time, the greatest probability of initiation appears to be across the KS/MO/NE/IA quad-state area. Supercells will be possible initially, with all modes of severe. An MCS is likely to evolve out of this activity by evening as it continues east toward IL. While significant severe is possible given the parameter space, will defer potential "sig" severe delineation to later outlooks when predictability is greater.
  9. Tim from Springfield (IL)

    Severe/Heavy Rain possibilities 8/16-8/18/19

    ILX not ruling out storms extending into Sunday, and the possbility of heavy rain again too in parts of the CWA: Area Forecast Discussion National Weather Service Lincoln IL 352 PM CDT Thu Aug 15 2019 .SYNOPSIS... Issued at 345 PM CDT Thu Aug 15 2019 Dry and pleasant conditions will continue through this evening across central and southeast Illinois with partly to mostly cloudy skies. Then more unsettled weather is expected to move into the area overnight into this weekend as a couple disturbances track into Illinois from the central plains. Ample cloud cover will keep moderate temperatures again on Friday, then more sunshine during this weekend into early next weekend, will warm temperatures to above normal levels along with more humid conditions. && .SHORT TERM...(This evening through Friday) ISSUED AT 345 PM CDT Thu Aug 15 2019 Weak 1015 mb surface high pressure ridge extending from Lake Huron and Lake Michigan down across IL was providing another dry day for central and southeast IL with partly to mostly cloudy skies this afternoon. Temps at 330 pm were in the upper 70s and lower 80s while dewpoints were in the upper 50s from Peoria nw and low to mid 60s se of Peoria. Scattered to broken cumulus clouds over IL at mid afternoon while thicker cirrus clouds were spreading east into parts of northern and western CWA at mid afternoon. These clouds were from MCS over nw MO/SW IA, far se NE and far ne KS. Consensus of CAMs take this MCS ESE across central MO and into central/sw IL overnight with increasing chances of showers and thunderstorms over much of CWA during overnight, and lingering into mid Friday morning. More redevelopment of scattered thunderstorms possible late Fri afternoon into Friday evening especially over central and southern CWA. SPC day2 outlook has marginal risk of severe storms over much of CWA, with a slight risk of severe thunderstorms sw CWA including Schuyler, Sangamon and Christian counties sw. The risk of severe storms now appears stronger during the late afternoon into mid evening over sw CWA if redevelopment does occur in this area due to more unstable conditions. There is a marginal risk of excessive rainfall for Fri into Fri night over much of central IL, while slight risk is in sw IL. Lows overnight mostly in the lower 60s with some mid 60s in west central IL. Highs Friday similar to today, around 80 central il and 80-85F in southeast IL. && .LONG TERM...(Friday night through Thursday) ISSUED AT 345 PM CDT Thu Aug 15 2019 Another MCS possible to affect parts of CWA during Friday night into Sat morning and have increase pops to address this possibly as model consensus have trended higher with qpf/pops then. SPC day3 outlook has marginal risk of severe thunderstorms Saturday along and north of I-72 while a marginal to slight risk of excessive rainfall too over much of area. Convection chances to become more isolated Sat afternoon, then models show another MCS to affect IA/WI/northern MO and into parts of central and northern IL during Sat night into Sunday morning. Excessive rainfall again possible but shifting further north over IL and may be a few strong thunderstorms too. Highs Sat in the 80s, warmest in southern CWA. Highs Sunday in the upper 80s to around 90F with heat indices Sunday afternoon in the mid to upper 90s, approaching 100F in southeast IL. Very warm and humid conditions look to continue from Mon thru Wed and a bit cooler on Thu. Mid/upper level ridge expands form the sw States toward IL early next week and also shifts the higher chances of showers/thunderstorms further north and east. Have dry conditions Sunday night thru Monday night, then slight chances of convection on Tue. Have 20-30% pops Tue night and Wed with a disturbance and weak front moving se thru area. &&
  10. Tim from Springfield (IL)

    Severe/Heavy Rain possibilities 8/16-8/18/19

    The Day 3 for Saturday hints that most of the action will be in the Dakotas and Nebraska, but marginal extends to Chicago and Milwaukee. With a Slight Risk eventually not ruled out: https://www.spc.noaa.gov/products/outlook/day3otlk.html ..Central Plains... A more nebulous surface pattern will exist south of I-80 over the Plains with only a weak surface trough over the High Plains, and an expansive area of moisture and instability. A moist and unstable air mass will exist over NE, KS, OK, MO, and IL, with possible early day storms from KS into IL. The strongest heating will occur over TX, western OK and into southern KS, and this will be an area for scattered afternoon storms as the capping is eroded. Other storms are possible along any outflow boundaries from earlier convection, but predictability is low this far in advance. While isolated to scattered strong to severe storms capable of wind or hail are possible, have opted to defer Slight Risk delineation to later outlooks when predictability is greater.
  11. Tim from Springfield (IL)

    Severe/Heavy Rain possibilities 8/16-8/18/19

    Just as soon as parts of central Illinois continue to recover from Monday night's severe weather (and the heavy rain last Sunday-Monday in parts of the sub), August severe weather returns tomorrow (Friday). Today's Day 2 shows most of the action in the Plains, but the slight risk extends into to the Metro East and the SPI area. And a hatched area across mid-MO to STL: https://www.spc.noaa.gov/products/outlook/day2otlk.html ...Central Plains into the Middle MS Valley... Showers and thunderstorms (remnant from an overnight MCS across KS) will likely be ongoing early Friday morning across central/southern MO. Outflow from these storms (which will likely extend back into central KS) will act as the effective front separating the warm and moist conditions across southern KS/MO/IL and the southern Plains from the cooler conditions across northern KS/MO and the remainder of the central Plains and middle MS Valley. This front is expected to act as the primary corridor for thunderstorm development, although two different forcing mechanisms appear possible. The first potential impetus for convective initiation is convergence along the front amidst diurnal destabilization. However, given the relatively warm layer between 850 and 700 mb and lack of stronger large-scale forcing for ascent, there is some question whether storms will be able to develop along the front during the late afternoon/early evening. If storms do develop, very strong buoyancy will contribute to strong updrafts capable of large hail and strong wind gusts. The lack of stronger vertical shear suggest storms should quickly become outflow dominant. Given the presence of a surface boundary, a brief tornado or two is also possible. The second impetus for convective initiation near the front is the low-level jet, which is expected to strengthen across the TX Panhandle, western OK, and southern KS Friday evening. Warm-air advection into the frontal zone is expected to result in the development of elevated thunderstorms from east-central KS, central MO, and far west-central IL. Mid-level flow will be stronger here and the potential exist for more organized storms capable of large hail. Isolated very large hail (i.e. diameter greater than 2") is possible.
  12. Tim from Springfield (IL)

    2019 Short/Medium Range Severe Weather Thread

    I don't usually like to start a severe thread, and don't mean to be late to the party on today's event either, but I started a new catch-all thread starting with today/tonight's action (including another MD in IA/N IL), going to early Wednesday:
  13. Tim from Springfield (IL)

    May 16-21 Severe Threats

    Don't mean to be late to the party, but another MD for IA/N IL for late tonight. 60% watch issuance likely. As discussed on the main short-term severe thread, Day 1 of the active pattern which includes marginals for parts of the subforum tonight and Saturday (plus Slight in IA Sat), and D4 (Sun) & D6 (Tue) risks already posted for parts of the sub too. https://www.spc.noaa.gov/products/md/md0643.html Mesoscale Discussion 0643 NWS Storm Prediction Center Norman OK 0714 PM CDT Thu May 16 2019 Areas affected...Southern and Eastern Iowa...Northern Illinois Concerning...Severe potential...Watch possible Valid 170014Z - 170215Z Probability of Watch Issuance...60 percent SUMMARY...An isolated severe threat is likely to continue developing across parts of southern and eastern Iowa eastward into northern Illinois. Wind damage and hail will be the primary threats. Weather watch issuance may be needed especially as uncertainty concerning convective coverage decreases. DISCUSSION...The latest surface analysis has a cold front from eastern Nebraska extending eastward across central Iowa into northern Illinois. An axis of maximized low-level moisture and enhanced convergence near an outflow boundary exists across northern Illinois where convective initiation has occurred in the last hour. Storm development in this area should remain relatively isolated, moving southeastward across north-central Illinois over the next hour or two. A wind damage and hail threat will be possible with this convection. Further to the west, An axis of moderate instability is analyzed across southern and eastern Iowa. The RAP is estimating MLCAPE values in the 1500 to 2500 J/kg range and shows 0-3 km lapse rates exceeding 8.0 C/km along this corridor. As a capping inversion decreases and low-level convergence becomes enhanced along the front, cell initiation is expected to occur. The latest short-term guidance suggests that scattered surface-based initiation will take place by 01Z to 02Z. In addition to the instability, the WSR-88D VWP at Davenport, Iowa shows 0-6 km shear near 35 kt suggesting that a severe threat may develop as cells increase in coverage. Wind damage and hail will likely be the primary threats. ..Broyles/Guyer.. 05/17/2019
  14. Tim from Springfield (IL)

    March 2019 Discussion

    LOT considering a WWA but have held off for now. Which surprises me considering tonight is St. Patrick's Eve, on a Saturday night to boot, and all the revelers that will likely be out on the roads who could get a messy surprise tonight. I would have probably gone ahead and pulled the trigger on a WWA for at least between the I-80 and I-88 corridors plus IKK. 000 FXUS63 KLOT 162036 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 336 PM CDT Sat Mar 16 2019 .SHORT TERM... 300 PM CDT Through Sunday... The quick hitting shot of accumulating snow from a clipper system late tonight into Sunday morning is the only forecast concern. Trends point toward a narrow band of about 2-4" of snow centered near the I-80 corridor. In the hardest hit areas, potential still exists for a few hours of moderate to heavy snowfall rates of 1"+/hour. However, have opted to hold off on issuing a Winter Weather Advisory for these reasons: lingering uncertainty in a setup like this with narrow banded nature and exact placement being essentially a now-cast; and lower impact timing and milder antecedent road temps. Will let evening shift take a look at observational trends for continued possibility of needing to issue an advisory. In response to elongated short-wave trough approaching the region tonight, lower and mid level warm advection will ramp up quickly and result in fairly strong frontogenesis from 925 mb up to 700 mb, noted on model cross sections. This will also be in the presence of unstable conditions aloft with negative saturated epv above the f-gen, along with strong omega centered in the DGZ. Furthermore, steep mid-level lapse rates of 7C/km or higher will be in place. The above ingredients continue to favor conceptually potential for a narrow but likely rather intense area of snow. Mesoscale nature of much of the setup makes for a very challenging forecast, especially considering that there isn`t much for upstream trends yet. A majority of the 12z guidance shifted northward with the main snow axis and several even brought northern edge of accumulating snow up to or a bit north of I-88 corridor including Chicago. In collaboration with WPC and neighboring WFOs, we followed suit and centered an axis of about 0.25 to 0.35" liquid equivalent QPF near/along the I-80 corridor, yielding swath of 2-4" snow amounts with ratios of 11-14:1. Some of the most bullish models had upwards of 0.40" QPF in max swath, lending concern toward the heavier convective rates with the snow and locally 4-5" accums depending exactly where things set up. With this all being said, RAP/HRRR guidance was consistently south of the guidance consensus through the day and a look at the latest 18z NAMs showed a bit of a southward shift as well. This all goes to show how uncertain/lower confidence pinpointing mesoscale driven snow banding is. The other wild card is the antecedent dry air under the surface high, plus typically sharper cutoffs with f-gen driven banding, making it such that the extent of minor accums up to an inch or two on the fringes will need fine-tuning. Temperatures will drop to the upper 20s to around 30 tonight, with much of the fall this evening until clouds roll in. Slowed the temperature rise in the morning with ongoing snow in portions of the area, as soundings indicate that the snow will end vs. any change to rain prior to tapering off. Extent/magnitude of any road impacts will be likely be tied to the narrow area that receives the heaviest rates and accums, considering mild road temps from today`s strong mid March sun. Nonetheless, those expecting to be out driving later tonight or Sunday morning should be prepared for possibility of some slick roads. Most or all of the snow that falls will quickly melt by mid day/early afternoon as at least partial clearing occurs and aforementioned strong March sun. For the rest of St. Patrick`s Day afternoon, expect steady northwest winds with temps most spots in low 40s, except upper 30s parts of northwest Indiana where clouds will clear latest and lakeside due to winds turning onshore. Castro &&
  15. Tim from Springfield (IL)

    Feb. 23 Storm Svr aspects

    If anything similar to some of the top 15 CIPS analogs verify Saturday, Central IL could also be in for a very long evening. Some big severe days in and near the current ILX CWA among these analogs: http://www.eas.slu.edu/CIPS/ANALOG/DFHR.php?reg=MV&fhr=F060&rundt=2019022112&map=tbl --#2 analog is 2/20/2014: http://www.eas.slu.edu/CIPS/ANALOG/Event.php?reg=MV&fhr=F060&rundt=2019022112&dt=2014022018 --#4 analog is 3/13/2006 0300 (9PM Mar. 12, 2006--just one hour after the first round of tornadoes hit the south and east sides of Springfield): http://www.eas.slu.edu/CIPS/ANALOG/Event.php?reg=MV&fhr=F060&rundt=2019022112&dt=2006031312 --#10 analog is 1/7/1989 1800--the same day as the F4 Allendale, IL tornado: http://www.eas.slu.edu/CIPS/ANALOG/Event.php?reg=MV&fhr=F060&rundt=2019022112&dt=1989010718