Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/10/20

Area Forecast Discussion
National Weather Service Duluth MN
644 PM CDT Sun Aug 9 2020 .SHORT TERM...(This evening through Monday night) Issued at 436 PM CDT Sun Aug 9 2020 An MCV over the CWA is progressing northeast, bringing showers and thunderstorms across northeastern Minnesota and northwestern Wisconsin. This system will continue to move east and we will get a break from storms before a cold front presently in over far northwestern Minnesota moves through tonight into tomorrow morning. Main threats this evening and tonight will be over 1 inch hail, 60+ mph winds, and isolated tornados. A drop in instability over the Arrowhead will limit how much severe weather will take place in that area tonight. The 18Z HRRR run shows the line of storms weakening over northern Minnesota before redeveloping over northwest Wisconsin. This is most likely due to northwest Wisconsin having MLCAPE values remaining in the 1500-3000 J/kg range overnight, according to RAP13. Effective bulk shear is also more favorable over northwestern Wisconsin at 30-40 kts versus around 20 kts in the Arrowhead. Monday, the cold front should exit eastern Wisconsin by mid morning. A high pressure associated with the back end of an upper level trough will approach from the Central Plains and keep us dry, cooler, and pleasant for Monday into Tuesday, with highs in the mid 70s. .LONG TERM...(Monday night through Saturday) Issued at 436 AM CDT Sun Aug 9 2020 Zonal flow is likely to inhibit precipitation Tuesday and Wednesday with gusty winds possible Tuesday afternoon. Temperatures are expected to remain warm, with highs in the low 80s for most locations on Tuesday and Wednesday. A shortwave moves into the Northland Wednesday night, leading to possible showers and thunderstorms. A messy pattern of scattered showers and thunderstorms is likely to set up for the latter half of next week into the weekend. Strong moisture advection of roughly 1.5-1.8 inches of PWAT from the south, along with a series of shortwave troughs will lead to a chance of showers and thunderstorms remaining in the forecast Thursday- Saturday afternoon. A cold front sweeps across the CWA Saturday evening into overnight, with rain expected to end following the passage of the front. Sunday is likely to be dry, with cooler temperatures in the mid 70s. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 643 PM CDT Sun Aug 9 2020 A couple different features were affecting the Northland this evening causing showers and storms. The first was an MCV over northern Wisconsin which should depart over the next 2 to 3 hours. The main threats with these storms is heavy rain and lightning. A cold front was moving through the far eastern Dakotas and western Minnesota and it was also causing showers/storms ahead of it. This front will continue east tonight clearing northeast Minnesota after 06Z and around or after 12Z for northwest Wisconsin. There will be a threat for a severe storm ahead of the front but the threat looks isolated with damaging wind, hail, heavy rain, and lightning all possible. IFR/MVFR conditions will be possible with the showers/storms and some patchy fog and stratus will also be possible until the front passes. Monday will feature VFR conditions with gusty westerly winds. && .MARINE... Issued at 436 PM CDT Sun Aug 9 2020 Showers and thunderstorms are possible tonight over Lake Superior. Some of these storms could produce hail, high winds, and lightning. Monday through Tuesday, winds will be 10-15 kts along the near shores and waves possible up to 3 ft in the Arrowhead. Tuesday, winds should increase to near 15 knots and gusts above 20 kts along the north shore. This could cause waves to be over 4 ft, especially from Silver Bay to Grand Portage. && .PRELIMINARY POINT TEMPS/POPS... DLH 59 77 55 83 / 40 0 0 0 INL 51 77 55 81 / 70 0 0 0 BRD 57 77 54 84 / 50 0 0 0 HYR 62 78 53 83 / 40 0 0 0 ASX 63 80 56 86 / 60 0 0 0 && .DLH WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. LS...None. && $$ SHORT TERM...Kossen/Melde LONG TERM...WFU/Melde AVIATION...Melde MARINE...Kossen/Melde
Area Forecast Discussion
National Weather Service Quad Cities IA IL
638 PM CDT Sun Aug 9 2020 00Z AVIATION AND SHORT TERM UPDATE .UPDATE... Issued at 637 PM CDT Sun Aug 9 2020 Area radars show the last of this afternoon`s round of convection exiting Stephenson County in northwest Illinois. Satellite imagery shows a sharp transition to clear skies over eastern Iowa, in an area of subsidence, drier air aloft, and capping behind the shortwave responsible for the departing thunderstorms over far northern IL and southeast WI. Absent an obvious upstream shortwave or MCV in the near term, the potential for additional storms this evening and even overnight, is looking increasingly remote. Most convective allowing models are latching onto this reality as well, with a dry forecast for overnight, then possible wave of showers and storms around sunrise. Have thus lowered pops this evening in an initial update and may be able to remove chances altogether through the rest of the night in later updates. && .SYNOPSIS... Issued at 302 PM CDT Sun Aug 9 2020 Clouds from morning storms and low-level WAA were dominant across much of eastern Iowa, northwest Illinois and far northeast Missouri early this afternoon, which was helping put a damper on the warm air mass building across the area. While temperatures were mainly in the low to mid 80s, light winds were helping pool the increasing surface moisture, with widespread dewpoints as of 2 PM in the mid to upper 70s. So despite the lack of sunshine, heat indices were still noticeable in the low to mid 90s. Where sun did peak out though, it felt closer to 100! The other story has been showers and storms, which have been scattered in nature and forced by leftover outflow boundaries and cold pools from morning storms. Dry conditions prevailed elsewhere, as guidance, our 12z sounding, water vapor imagery and SPC mesoanalysis continued to hint at a persistent lid of warm and drier air aloft, capping any potential storm development. This sort of scenario is what will play out for much of the short term period. && .SHORT TERM...(This Evening through Monday) ISSUED AT 302 PM CDT Sun Aug 9 2020 Key Messages: 1) Low confidence forecast with showers and storms possible through the entire period. 2) Storms that tap into the high instability may become strong/severe. As is the case with the previous few days, the forecast confidence of the short term is low as there is much that could influence where storms form or if they even develop at all. As mentioned in the previous discussion, we have a lot of instability as steep mid level lapse rates around 7-8 C/km are promoting MUCAPE values around 3000- 4000 J/kg. There problem goes back to the warm/dry air around 700 hPa, as it continues to act as a lid and inhibit any widespread storm development. This means forcing for any storm is going to be by remnant cold pools leading to enhanced surface convergence, outflow boundaries or where pooling dewpoints increase surface instability and promote development. Convective allowing models and most deterministic global models, unfortunately, do not handle these situations extremely well, which leads to a diverse set of solutions and a lot of uncertainty. With this forecast, continue to advertise slight chance to mainly chance POPs across the area during times at which storms appear to be most favorable. The first comes this afternoon and evening as outflow boundaries and an MCV from morning storms in central Iowa increase low-level convergence. Coverage will remain fairly scattered according to the latest CAMS, but any storm that develops could become strong if it becomes surface based as it taps in the robust instability. The primary threats would be damaging wind gusts and torrential rainfall. There is a lower risk for large hail, but that will be dependent on how robust updrafts can get as there isn`t a great deal of shear to work with. SPC continues to advertise a marginal risk of thunderstorms across the area. The next chance will come later tonight as there is a potential for a developing MCS in Minnesota and western Wisconsin to move south into the area. The NAMnest, NSSL-WRF and ECWMF are most bullish on this solution as they show the complex riding the MLCAPE gradient south across the area. Meanwhile, the NAM, GFS, CMC and HRRR show mainly dry conditions to only an isolated storm over our area with the complex staying to the north. If storms were to develop, heavy rain and wind gusts would accompany them. For Monday, a cold front will approach the area from the north, and looks to be the focus for the next round of thunderstorms. Much of this will depend on how the morning evolves. If we end up remaining dry, storms should have less trouble initially firing along the front across our north during the afternoon. If we do have morning activity, then storms would likely form more south of the I-80 corridor once there has been enough time for the atmosphere to recover. SPC maintains a marginal risk for all of eastern Iowa, northwest Illinois and northeast Missouri for the afternoon and evening, with damaging wind gusts and heavy rainfall the primary threats. Temperatures for Monday will be dependent on how much cloud cover is present and storm coverage. However, the air mass overhead still supports afternoon highs in the upper 80s to near 90, especially along and east of the Mississippi. Heat indices will climb back into the mid to upper 90s, to near 100 in spots. .LONG TERM...(Monday Night through Sunday) ISSUED AT 302 PM CDT Sun Aug 9 2020 Monday Night A few strong or severe storms are possible mainly south of I-80 with damaging winds the primary threat if any bowing segments were to develop. Confidence is low on the details regarding coverage and exact timing. But with moderate to high instability residing along and south of a weak cold front, the potential is there for an organized storm cluster or two, with the most likely timing between 4 PM - 10 PM. Tuesday and Wednesday Great Lakes high pressure, with extension over eastern Iowa and northwest Illinois, will bring less humid conditions for Tuesday and Wednesday, along with seasonable highs in the low to mid 80s. An isolated shower or storm is possible during peaking diurnal heating, but most of the CWA will stay dry through at least the middle of the week. Thursday On Blocking upper-level flow will develop late in the week as a ridge expands over the Great Lakes and across eastern Ontario. A remnant convectively induced vorticity max, guided by zonal mid-level flow, will become cut-off over the Mid to Upper Mississippi Valley as its eastward progression is halted by the aforementioned ridge. This feature could result in low coverage showers and storms. However, latest model guidance has backed off on QPF potential. For now have low chances Thursday into the weekend, generally 20-30%. Overall there are no strong signals for widespread or heavy rain late this week into the upcoming weekend. Otherwise, typical mid August weather is anticipated with highs in the mid/upper 80s and humid conditions (mid 60s to low 70s dewpoints). Uttech && .AVIATION...(For the 00Z TAFS through 00Z Monday Evening) ISSUED AT 637 PM CDT Sun Aug 9 2020 VFR conditions will continue this evening, then there will be an increasing potential for at least light fog and low clouds due to moisture convergence ahead of a weak front. MVFR conditions are thus brought in around 09Z at CID, DBQ and MLI, with DBQ most likely to see a period of IFR due to ceilings below 1000 ft agl Monday morning. All sites should see an improvement to VFR by mid morning with light winds veering to more westerly. There will be increasing chances for thunderstorms during the day as a cold front approaches and these are mentioned in prob30 groups at CID, DBQ and MLI. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && $$ UPDATE...Sheets SYNOPSIS...Speck SHORT TERM...Speck LONG TERM...Uttech AVIATION...Sheets
National Weather Service Kansas City/Pleasant Hill MO
648 PM CDT Sun Aug 9 2020 .Discussion... Issued at 157 PM CDT SUN AUG 9 2020 Primary forecast focus is on current showers and thunder and a second round on Monday. A challenging forecast scenario through the the morning and present. An early morning MCS across southeastern South Dakota and northeastern Nebraska laid down a persistent outflow that raced southward down the Missouri River valley. This feature combined with a weak 500mb short wave trough and considerable isentropic ascent, sparked widespread showers and thunder across the area through sunrise into the afternoon. The boundary reached the Ozark plateau through noon as it slowed, becoming an east west oriented boundary. Along and north of this focusing mechanism, showers and thunderstorms continue to persist and slowly work their way eastward with the track of the upper wave. No surprise, guidance has handled this situation with less than stellar accuracy. The only standout was the HRRR and HRRRx, the latter of which caught on early and has maintained a usability into the afternoon. Expectations are for the current (1:30 PM) activity to continue to slowly build east, with rain ending through the late afternoon, west to east. Estimate a 5 to 7 PM end time for central Missouri, as an remaining activity shifts to the east. It`s suffice to say, the heat advisory in effect will likely not pan out for a decent part of the area due to the ongoing rain and cloud cover. However, locations in northwest Missouri and northeast Kansas have cleared out and temperatures have started to increase. Given dew points in the lower 70s F, it won`t take much, temperatures in the lower 90s F, to get heat index values around 100 F, maybe higher. Overnight, early solutions suggested some rain chances, but it`s looking dry across the region, at least through sunrise. A weak short wave trough riding the general flow of the base of the larger trough centered over the northern Plains and Canadian Prairies across SD/NE, may result in some residual precipitation across northwest Missouri/northeastern Kansas. Into the afternoon an elongated frontal boundary will sink southward into the afternoon. A sizable EML spread across the warm sector will inhibit convective initiation well into the late afternoon/early evening. Considerable warm air advection into eastern kansas and western Missouri will result in an extremely unstable airmass. Not to rehash the SPC Day Two outlook, but modest deep layer shear will be a limiting factor. However, steep lapse rates will promote strong downdrafts and as scattered convection fires in proximity to the boundary, the strongest storms will pose a wind gust threat. Overnight into early Tuesday, as the low level jet increases after sunset, a few complexes may develop moving south and southeast across the Ozarks through daybreak. The severe concerns will drop off through the early Tuesday morning. The remainder of the week will be marked with continual shower and thunderstorm chances, especially Thursday into Friday as another short wave trough moves through the region. Temperatures will top out in the upper 80s and low 90s each afternoon. && .Aviation...(For the 00Z TAFS through 00Z Monday Evening) Issued at 648 PM CDT SUN AUG 9 2020 Currently VFR at all terminals with showers and thunderstorms remaining well south of the terminals this late afternoon. VFR conditions are expected to prevail through the period. LLWS will be a concern again overnight tonight through sunrise Monday. Attention then turns to the threat for showers and thunderstorms Monday afternoon/evening as a cold front will approach the region from the northwest. For now have introduced VCTS beginning at 21z Monday (20z at STJ). There will be the potential for strong to severe storms given very large instability, so strong thunderstorm wind gusts and perhaps even some large hail could briefly impact the terminals. The front appears likely to slow down or even stall Monday afternoon across NW Missouri, so confidence in the precise time of the wind shift is low at the current moment. For now have introduced a wind shift to northerly behind the front at STJ by 20z and all other terminals by 23z Monday. && .EAX WATCHES/WARNINGS/ADVISORIES... KS...Heat Advisory until 8 PM CDT this evening for KSZ025-057-060- 102>105. MO...Heat Advisory until 8 PM CDT this evening for MOZ001-002-011>013- 020-021-028>030-037-038-043-044-053-054. && $$ Discussion...Kurtz Aviation...BMW
Area Forecast Discussion
National Weather Service Green Bay WI
724 PM CDT Sun Aug 9 2020 Updated aviation portion for 00Z TAF issuance .SYNOPSIS... Issued at 330 PM CDT Sun Aug 9 2020 A round or two of thunderstorms tonight into Monday, then turning much less humid but with above normal temperatures continuing throughout the upcoming work week. The large scale pattern across North America won`t change much during the next 7 days. The subtropical ridge will remain stretched out across the central and southern CONUS, with a seasonably strong band of westerlies to the north across Canada and the far northern CONUS. Within the westerlies, a ridge position was off the West Coast, with a trough position over the Intermountain West. Those features will remain in place for a few days, then the pattern will become slowly progressive. The humidity will drop significantly early in the period, then slowly creep back upward thereafter. High temperatures should remain slightly to modestly above normal throughout the period. The dry air may allow low temperatures to drop AOB normal for a few days during the early to middle part of the period, otherwise mins will probably be at least slightly above normal. The pattern will probably result in AOA normal precipitation, most of which will fall early in the period. A several day long stretch of dry weather is likely during the upcoming work week, then rain chances will gradually begin to increase. && .SHORT TERM...Tonight and Monday Issued at 330 PM CDT Sun Aug 9 2020 A quiet early afternoon ongoing across the area, as the area is situated in the warm sector, with a mix of low, mid and upper level clouds spreading across the state. It was warm and humid, with temps climbing into the 80s and dewpoints in the upper 60s and lower 70s, producing heat index readings in the middle 80s and lower 90s. As expected, a very messy upstream pattern with multi areas of storms ongoing through the late morning and early afternoon. Forecast challenge will be trying to pin down where/when the best chances for showers/storms will occur and the prospects for severe weather. For tonight...CAMs continue to struggle with the complicated set up. Currently there are clusters of storms across northeast IA/southern WI, eastern MN, northwest WI and eastern SD and far northwest MN. Each one of these will either bring a chance of storm activity to the area or impact the chances of that happening. First, the storms across far northeast IA and southwest WI continue to hold its own, despite the lack of bulk shear, moving east/eastnortheast. This will continue to track toward mainly east central WI, but the models that do show this feature have it weakening. Second, the well defined MCV that has been tracking across central MN. This feature has been behaving so far, fighting some subsidence and weak capping, but it is moving into a more favorable environment, so will likely see an uptick in activity in the late afternoon/evening as it approaches. This will track into the Northwoods, bringing the best chance for widespread activity through the early evening hours. If the system becomes more mature, activity along the southern edge could expand, impacting more of the area, but it will be fighting the cap. Finally, the convection across eastern SD and far northwest MN associated with the actual cold front and shortwave. This has the most organized severe weather threat with the best dynamics with several ongoing warnings. This activity will continue to drop southeast through the night, but again, models differ on how long it will last as it enters a more stable/worked over airmass across northeast MN where there is ongoing convection. The boundary/outflow from this feature could help kick off additional storms later tonight, as it reaches northwest WI where more instability should be present. Model soundings still showing a cap in place across the area, so expect any activity outside the more organized areas will struggle to develop/sustain itself. Latest runs of the HRRR is one of the better performing models, so will lean on its guidance, but keep chance POPs going for most locations for much of the night as confidence remains on the low side on how everything will play out tonight. Looking at the severe weather threat, SBCAPE of 2500-3500 J/kg were found across the area this afternoon, despite the cloud cover for much of the day. Low-mid level lapse rates continues to steepen to between 7-9C/km. Bulk shear the greatest (25-35 kts) across north central WI, with values falling to around 15 kts across east central WI. So atmosphere conducive for severe weather, if we can get any area of organized convection. Damaging winds looks to be the main threat, with hail possible as well. The other hazard will be heavy rain and flooding as PWATs remain between 1.5-2.0". It will be another warm and muggy night across the area, with lows dropping into the middle 60s north to the lower 70s in the Fox Valley and lake shore and dewpoints remaining in the upper 60s to around 70. For Monday...surface cold front and shortwave sweep across the area, bringing additional chances for showers/storms. Models again not in the best agreement due to not handling the overnight activity very well. There could be some left over activity across a portion of the area to start the day, then focus will be along the front as it passes through the area, reaching the Fox Valley and lake shore in the late morning or early afternoon. If the front slows at all, chances for a stronger round of storms increase, along with possibly a severe storm. Models that do not show much activity tonight favor a higher end event on Monday (HRRR showing 3500+ CAPE and 30 kts of bulk shear for the front to work with). So this will need to be watched. Locally heavy rain and flooding will be possible with PWATs of nearly 2" pooling ahead of the front. Warm and humid conditions will continue in the morning, then the drier air will filter in behind the front, but won`t reach the Fox Valley and lake shore until evening. .LONG TERM...Monday Night Through Sunday Issued at 330 PM CDT Sun Aug 9 2020 Quiet, dry weather is likely for at least a few days at the start of the long-term portion of the forecast as a weak anticyclone slowly shifts across the region. Westerly flow aloft will limit the cooling associated with the high, but the drop in humidity will be much more noticeably. Overall, saw no reason to deviate significantly from the standard forecast initialization grids generated from a broad-based blend of guidance products. && .AVIATION...for 00Z TAF Issuance Issued at 723 PM CDT Sun Aug 9 2020 More widespread thunderstorm activity that was anticipated this evening, thus far not panning out due to more clouds than expected across parts of the area today and elevated warm layer that has generally capped the environment. Through at least mid night or so, appears best chance for any scattered thunderstorm activity will be confined across the far northern Wisconsin in vicinity of convectively induced circulation. A few of these storms storms may contain gusts to 40 kts and brief MVFR cigs and vsbys. Appears the brunt of this activity will remain NNW of RHI TAF site through late evening. Later tonight, primary frontal boundary over NW Minnesota will continue to push southeast into far northwest Wisconsin after midnight. Latest short-term guidance still suggests that some scattered thunderstorm activity may initiate along this front and perhap impact AUW/CWA and RHI sometime in the 09 to 12 UTC time frame. However, given poor performance of the guidance lately and elevated warm layer aloft, confidence is low on location and timing. Elsewhere overnight, copius moisture may lead to low cloud formation and fog across parts of central and northcentral Wisconsin as well. This may bring some areas of IFR cigs and vsbys across this area. Frontal boundary will push east across the entire forecast area during the day on Monday and may kick off a few more showers and thunderstorms prior to 21 UTC especially across the Fox Valley. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS.......Skowronski SHORT TERM.....Bersch LONG TERM......Skowronski AVIATION.......ESB
Area Forecast Discussion
National Weather Service Grand Rapids MI
1143 PM EDT Sun Aug 9 2020 LATEST UPDATE... Aviation .SYNOPSIS... Issued at 315 PM EDT Sun Aug 9 2020 - Fading Storms into Early Monday, More Possible Monday Night - Quieter Weather Until Next Weekend && .DISCUSSION...(This evening through next Sunday) Issued at 315 PM EDT Sun Aug 9 2020 This pattern is notoriously difficult for pinning down who`s likely to get rain and who isn`t. Rich, low level moisture with modest instability but lack of deep layer forcing leads to question marks about storm chances through early Tuesday. The high resolution CAMs failed to signify a heavy rain threat earlier this morning from Sheboygan, WI across the lake through Pentwater and eastern Oceana County. The prior 00z run of the HREF`s 24-hour probability matched mean rainfall had less than 0.10" for this area but in reality there was a swath of 1"-2" across Mason/Oceana Counties and an even heavier swath of 3"-6" near Sheboygan. The HREF did indicate PWAT values of around 1.8" in this area as slow moving storms developed but the five members of the HREF didn`t catch the magnitude of rainfall as of their 00z initializations. Fast forward to tonight and Monday, and similar challenges exist in forecasting thunderstorm chances. While a 30 knot LLJ will be moving into Missouri and Illinois by 06z tonight, it will be buckling SE and we`ll miss out on the best low level moisture convergence. The 500 mb winds never get above 20-30 knots and deep layer shear will be 20 knots or lower, so storm organization will be impacted and propagation may quickly become outflow dominated if any manage to cross the lake overnight. Storms will likely fade around sunrise but some heavy downpours and residual gusty winds are possible mainly near and west of US 131 very late tonight into Monday morning. I could envision the remnant outflow boundary potentially kicking off a shower or storm primarily east of US 131 during the day Monday but the coverage is questionable. Still, localized downpours would be possible. The better chance for thunderstorms exists Monday evening into Monday night as better forcing is present, with the right entrance region of the upper level jet moving in and sfc based CAPE in the 1000-2000 J/kg range. We are not expecting severe weather at this time. The main threat would be locally heavy downpours with some ponding of water on roads. Finally, there is a possibility that a few locations mainly near and west of US 131 could pick up a few inches of rain through Monday night (eg. the 06z/12z HRRR runs show this), but feel the geographic scope is likely to be too localized to cause widespread impacts. Rain rates in the heavier storms could exceed 1"/hour, but coverage would be limited enough to preclude a threat to most rivers and streams, and most locations would not get substantial rain. -- Quieter Weather Until Next Weekend -- Most medium range guidance suggests the second half of Tuesday into Friday should be dry for most areas (aside from an isolated shower or storm here or there). Dew points are forecast to drop into the 50s and 60s until rebounding back toward 70 for the weekend. We may see a scattering of showers and storms by that time. && .AVIATION...(For the 06Z TAFS through 06Z Tuesday) Issued at 1140 PM EDT Sun Aug 9 2020 Primarily VFR conditions are forecast overnight and Monday. However brief reductions to MVFR/IFR are possible overnight and on Monday due to scattered showers and storms. The relatively best chance for some thunderstorms at all the terminals will come mid to late Monday afternoon through late Monday evening along and just out ahead of the cold front. && .MARINE... Issued at 315 PM EDT Sun Aug 9 2020 Waves will build into the 2 to 4 foot range later tonight and into Monday out ahead of a front moving in late Monday night. Winds will be from the S/SW. Behind the front, winds will turn more northwesterly but generally 1 to 3 footers are expected Tuesday. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...None. && $$ SYNOPSIS...Hoving DISCUSSION...Hoving AVIATION...Laurens MARINE...Hoving
Area Forecast Discussion
National Weather Service Lincoln IL
804 PM CDT Sun Aug 9 2020 .SYNOPSIS... Issued at 245 PM CDT Sun Aug 9 2020 Periods of thunderstorms are expected through Monday night across central and southeast Illinois, with potential for producing an inch or two of rainfall. Some of the storms may be strong to locally severe, with damaging winds the main concern. In between the storms on Monday, heat index values of 100 to 105 degrees are likely near and west of I-55. && .UPDATE... Issued at 800 PM CDT Sun Aug 9 2020 Evening convection did not really materialize over central Illinois except for an isolated storm just south of the forecast area. Backed off on PoPs this evening but will continue to monitor, especially an area of accus south of I-72 and west of I-57 which appears to be the most likely area if anything were to happen this evening. Otherwise best chances will be after midnight when low level jet increases across the region with scattered thunderstorms still expected. && .SHORT TERM...(This evening through Monday night) ISSUED AT 245 PM CDT Sun Aug 9 2020 Earlier MCV that brought the rain to the southeast CWA stands out nicely on visible satellite imagery this afternoon, centered just west of Evansville and moving east. Convection over central and southern Missouri has shown some weakening as of late, though the HRRR suggests some development along an associated surface boundary in west central Illinois later this afternoon. Will include some 20% PoP`s west of highway 51 for late afternoon and early evening with this feature. Main focus for thunderstorm activity is expected near and after midnight, as an MCS develops over the region. Some variations noted on the convective allowing models as to where this takes place, with the 4 km NAM suggesting an initiation associated with convection currently in southwest Wisconsin/northeast Iowa, while the 12Z HRRR and ARW place it closer to our area. Will go with likely PoP`s late tonight and early Monday across the heart of the forecast area, along a northwest/southeast axis. Secondary round with the front itself has better agreement with an arrival northwest of the Illinois River very late Monday afternoon, and pushing across the forecast area during the evening. Between these two periods, potential exists for 1-2 inches of rain exists across most of the forecast area. A secondary concern involves the heat on Monday. Assuming a period of sunshine across the western CWA behind the MCS, highs should reach the lower 90s with heat index potentially around 105 degrees from about Havana and Springfield west. However, with the uncertainty regarding the cloud cover, will hold off for now on any heat advisories. .LONG TERM...(Tuesday through Sunday) ISSUED AT 245 PM CDT Sun Aug 9 2020 As the upper wave passes by to our north Monday night, we get into more of a zonal flow, which will allow the early week front to become more stationary to our south on Tuesday. Highest PoP`s will be near and south of I-70, while high pressure over the Great Lakes tries to get some drier air in here for a time. As we get later in the week, focus shifts more toward diurnal convection as periodic upper waves pass through the region. General shift for the Friday/Saturday system has been away from the closed upper low over our region, though the Canadian model still lingers this for a time. Thus, an extended period of rain is appearing less likely at this point. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 640 PM CDT Sun Aug 9 2020 Multiple thunderstorm chances are the primary aviation forecast concern tonight through Monday, though confidence in any specifics remains low at this time. Early this evening, several models indicated the possibility of scattered thunderstorms currently over northern Illinois extending southward into central Illinois, however, satellite imagery does not show any convection imminent in this area so dry conditions currently appear favored this evening. Overnight, increasing low level jet will result in LLWS and scattered thunderstorm development. Storm chances will diminish after daybreak Monday. An approaching cold front should bring yet another round of showers and storms to the terminals, but at this time appear most favored just beyond the current TAF period. Outside the influence of storms SSE/SSW winds are expected to prevail through the period. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Deubelbeiss SYNOPSIS...Geelhart SHORT TERM...Geelhart LONG TERM...Geelhart AVIATION...Deubelbeiss
National Weather Service Jackson KY
1118 PM EDT Sun Aug 9 2020 .UPDATE... Issued at 1118 PM EDT SUN AUG 9 2020 The previous update did not pan out, as incoming convection dissipated just before it entered the forecast area. A few light showers may still move through portions of Wayne county tonight, but it appears that any other areas of rain will dissipate as they approach the area and should not make it in. The next round of rain we should see will be later tonight. The other elements of the forecast were freshened up using the latest hourly obs. The weather and PoP grids were adjusted based on current radar trends. UPDATE Issued at 918 PM EDT SUN AUG 9 2020 Updated the forecast grids to account for an area of showers and isolated storms that is currently moving into the southwestern counties of our forecast area. The activity is slowly dissipating, but it looks like it will hold together long enough to affect some of southwestern counties. Will continue monitor the ongoing convection and may need to update again toward the end of the shift depending how well the showers and storms are still doing by then. && .SHORT TERM...(This evening through Monday night) Issued at 405 PM EDT SUN AUG 9 2020 19z sfc analysis shows high pressure still holding on over far eastern parts of the state. This has provided a mostly sunny day as even the high clouds from convection to the west are just now encroaching our southwest counties. The sunshine helped temperatures peak a couple of degrees higher than yesterday in the upper 80s for most places. Meanwhile, amid light winds, the dewpoints did manage to drop a tad from morning and are now in the low and mid 60s. The models remain challenged aloft through the short term portion of the forecast. While they all do show a key impulse moving into central Kentucky this evening and weakening overnight over eastern Kentucky, the magnitude and placement of this features is a little off in each. Some weakness in the mid level heights continue into the day Monday and that night as the southern ridge further retreats to the southwest. During this time additional weak energy packets will pass through the area maintaining an active pattern. Given the uncertainty have favored the blended NBM model as the starting point for the grids with a strong lean on the CAMs consensus for PoP and QPF specifics tonight into Monday morning. Sensible weather will feature a mild night with increasing clouds expected as a more active weather pattern takes shape. The remnants of an MCS or two could spread into the western parts of the Cumberland Valley late tonight, per many of the CAMs - moreso the NAMNest than the HRRR - with the threat continuing into the day Monday. While these clouds should limit the fog development to a certain extent overnight, the northeast may be cloud free long enough for some river valley fog similar to this morning. Likewise, expect a bit more of a ridge to valley temperature split over the northeast compared to the rest of the CWA into Monday morning. Scattered showers and thunderstorms are then expected to be around during the day Monday with some diminishment expected after dark and with the loss of daytime heating. However, leftover boundaries and favorable upper level support will mean a small threat for convection continuing that night and into Tuesday morning. Adjusted the NBM high temperatures down a notch on Monday with the expectation of more cloudiness and some storms around. Did also tweak the northeast ridge and valley temperatures tonight. As for PoPs, mainly adjusted the late day PoPs on Monday more toward a diurnal pattern and in conjunction with the upper support. .LONG TERM...(Tuesday through Sunday) Issued at 314 PM EDT SUN AUG 9 2020 The upper level height rises will have some weaknesses, as the Ohio Valley remains in the periphery of this upper level ridging centered across the Southwest US. These weaknesses will come in the form of weaker upper level perturbations and will lead to increased chances of mainly afternoon and evening showers and thunderstorms Tuesday into Wednesday. However, given the ample instability and moisture we could see some of this come in the form of MCS activity, but uncertainty remains given this is more mesoscale driven process. After this the synoptic pattern become more zonal aloft leaving us vulnerable to more weak shortwaves. However, it looks like the overall pattern would lead to most diurnally driven convection by the end of this week into next weekend. The active pattern could lead to some strong storms and even some flooding potential as we move through the week, but still plenty of uncertainty on where any issues would arise given this will depend on mesoscale features. In terms of temperatures, we will average above normal through the period, but there is bust potential given the possibility of afternoon convection. The overall synoptic pattern for the long term period seems to be largely agreed upon by the various model suites. Given this was able to keep the NBM going for much of the forecast. That said, did keep the likely PoPs presented Tuesday into Wednesday mainly in the afternoon, but lowered to chance for most in the later part of the extended given some uncertainty on features this far out. Outside this only minor changes were needed to handle the ridge/valley temperature differences usually seen in both highs and lows compared the NBM more uniform output. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) ISSUED AT 754 PM EDT SUN AUG 9 2020 VFR conditions will prevail through late tonight for most of the area, before some valley fog threatens once again. This should be less extensive compared to the previous few nights, as some clouds will be on the increase from the west late in the period. A new forecast issue has arisen since the previous TAF was issued. A small complex of showers and storms has formed in central KY, and is heading toward the southwestern portion of our forecast area. If these showers and storms hold together, SME and LOZ could see some impacts from them. Due to uncertainty in the potential for the storms to hold together, have only went with VCTS at SME and LOZ for now to handle any storms that may affect those two airports. Will monitor this situation closely and will amend the LOZ and SME TAFs as necessary through 3Z this evening. After that, some small chances for showers and thunderstorms will return again to the Cumberland Valley on Monday morning, but the TAF sites there should remain clear keeping conditions as VFR once any fog clears. Winds will average less than 5 kts through the period. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...AR SHORT TERM...GREIF LONG TERM...DJ AVIATION...AR
Area Forecast Discussion
National Weather Service North Platte NE
628 PM CDT Sun Aug 9 2020 .SHORT TERM...(This evening through Monday night) Issued at 258 PM CDT Sun Aug 9 2020 Near term concerns revolve around a few rounds of isolated to widely scattered thunderstorms later today and again early Monday morning across portions of western and central Nebraska. Surface boundary currently draped across the Sandhills into southwest Nebraska will be the focus of a possible round of thunderstorms later this afternoon and evening as weak energy moves off the Front Range and east onto the High Plains. Southeast of this boundary, a humid airmass remains in place with mid 60 to mid 70 dew points and high temperatures once again in the upper 80s and low to mid 90s. Northwest of this boundary, drier air in place with a slight downslope component to the winds has helped temperatures spike into the 90s with a few locations seeing upper 90s but heat indices remain in check. Much like Saturday, the environment is supportive of strong to severe thunderstorms...steep mid-level lapse rates of 8- 9 C/km...MLCAPE values climbing above 2500 j/kg...0-6km BWD values of 30 knots. The question will be if a storm as able to break the cap. The morning RAOB advertises h85 and h7 temperatures of 25 and 15 degrees C respectively and though low-level moisture quality has increased, so has mid-level temperatures according to RAP analysis. Forcing is much weaker today as well with lack of an appreciable shortwave, only modest height falls, and weaker low-level convergence. The LLJ is also forecast to be weaker this evening than last night. All these combined suggest coverage likely to be isolated in nature. As such, have limited PoPs to Slight Chance across the area. Should a storm develop, large hail and damaging wind gusts will again be the main concerns. Though recent performance hasn`t been exemplary, hi-res guidance suggests isolated storms that don`t maintain themselves much longer than an hour or two, further backing this idea that many locations likely remain dry tonight. Should storms develop, expect activity associated with this round to exit the area to the east shortly after Midnight. The second potential round for thunderstorms will occur late tonight into early Monday morning. This will likely be attributed to stronger mid-level frontogenesis as high pressure diving south in the area. This forcing for ascent will be aided by some elevated instability, helping drive some isolated to potentially scattered thunderstorms mainly for areas north of Highway 2. Recent trends of hi-res guidance have shifted this threat north, mainly across far southern South Dakota as opposed to north central Nebraska. This trend will need to be monitored for further adjustments to the PoPs for Monday morning. Do believe we will see some activity move into north central Nebraska as the fgen bands, mainly focused in the h85- h7 layer, will progress north to south with time and are expected to eventually work their way into Nebraska. Greatest potential will again be across far north central Nebraska. Though organized severe weather is not expected with this activity, a few stronger storms capable of hail cannot be ruled out given some overlap of modest shear and instability. Lows overnight will fall into the 50s to low 60s. Precipitation will gradually diminish through the morning, leaving the bulk of the daytime dry for Monday. Temperatures will be cooler as the surface boundary sags south into Kansas and Canadian high pressure moves overhead. Expect values nearly 5-10 degrees below normal for mid-August with daytime highs in the upper 70s to low 80s under partly cloudy skies. Lows Monday night will hover in the upper 50s. .LONG TERM...(Tuesday through Sunday) Issued at 258 PM CDT Sun Aug 9 2020 Beginning 12z Tuesday. High pressure departs by early Tuesday with the area in general southerly flow behind the departing feature. This will not only help to advect higher moisture into the area but also allow temperatures to trend upwards over the rest of the week. Near daily rain and thunderstorm chances will exist as multiple disturbances move through the area. The strongest of these systems looks to move through Tuesday and with some modest upper-level support, may bring another round of strong to possibly severe thunderstorms to the area. A lot of uncertainty with respect to this so stay tuned. Highs return to the 90s for most if not all locations by Wednesday and continue into the weekend before another frontal boundary brings precipitation chances and a brief cooldown. Though temperatures will be above normal for much of the upcoming week, heat concerns look to be fairly low as humidity will be greatest to the east of the area. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 626 PM CDT Sun Aug 9 2020 The latest NAMnest solution, fires off a round of thunderstorms, generally east of a KBBW to KANW line after 00z this evening. This activity will remain east of the KLBF and KVTN terminals and will not be an impact. Some minimal high cloudiness may move into the area overnight into Monday with cloud decks around 25000 FT AGL. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Jurgensen LONG TERM...Jurgensen AVIATION...Buttler
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
910 PM CDT Sun Aug 9 2020 .UPDATE... 905 PM CDT A line of showers and thunderstorms continues across far northeast IL after paralleling the WI/IL border earlier this evening bringing much needed rain to those areas. A resultant outflow boundary is helping to fuel further development to the south of the current thunderstorm complex. Scattered showers and thunderstorms remain possible the next few hours as this line gradually drifts southeast along the lakeshore. Plenty of subsidence exists to the northwest of the current area of showers with clear skies across SW Wisconsin into much of Iowa. An apparent boundary extends from NW Nebraska into SE Minnesota late this evening with a couple thunderstorm clusters having developed along it. Due to expected clearing and ample surface moisture, have added a mention of patchy fog for our northwestern zones late tonight into early tomorrow morning. A considerable amount of uncertainty remains with regard to our thunderstorm chances over the next 18-24 hours. Significant variability between model runs has made pinpointing the expected evolution of various thunderstorm complexes quite challenging. It remains unclear as to whether any outflow/cold pool interactions and resultant thunderstorm development could cause a line of thunderstorms to move through the area late tonight into early tomorrow morning. Several models have backed off on this scenario, with an alternate scenario, such as some of the latest HRRR runs, suggesting that more scattered convection develops at the nose of the LLJ as a weak shortwave moves overhead. Regardless, showers and thunderstorms remain possible overnight tonight into early tomorrow morning. Of slightly greater certainty is that thunderstorms will develop ahead of and along a surface cold front as it pushes through the area tomorrow afternoon and evening. The overall coverage and severity of storms is what remains somewhat in question and will depend on how well the atmosphere is able to recover behind any morning convection. Petr && .SHORT TERM... 242 PM CDT Through Monday night... Convective trends continue to pose the primary challenge for the near term and unfortunately forecast confidence is not high. The activity presently moving into western portions of the forecast area as of mid afternoon poses the first question. As anticipated, so far most of these cells have struggled to achieve any sort of sustained organization but a few clusters have managed to hang together for an hour or so at a time. This is handled by a mention of isolated to scattered thunderstorms gradually expanding eastward through the remainder of the afternoon which seems to be a reasonable approach given the lack of focused forcing and even some lingering low level capping that may be in place. Overnight toward the predawn hours, an increasing though not strong low level jet will provide support for the next favorable period of activity in the form of elevated convection. As the jet veers and weakens toward morning the focus likely will shift south, but there appears to be a broad enough warm and moist low level flow to include at least a chance of TS areawide. Later in the day and into the evening Monday the third favorable period of activity takes shape ahead of a cold front approaching from the northwest. FROPA itself appears likely in the late afternoon toward the northwest and late evening in the southeast. Even with this boundary providing a bit better focus for forcing, it is not clear whether convection will develop in the prefrontal warm sector or be tied closer to the boundary itself. Some locations may also remain dry with the frontal passage but that appears a less likely scenario. Either way, barring any disruption from earlier activity, thunderstorm chances would increase later in the day and toward early Monday evening as boundary layer heat and humidity maximize and midlevel lapse rates steepen, then diminish overnight in the cooler and drier postfrontal northwest flow. During peak heating there is also a bit stronger flow aloft which may support some stronger or more organized convection. Heavy rain is also a concern with PWATs approaching two inches. Temperature trends and heat indices would be the other concern for Monday. Cloud cover may keep temperatures from getting quite as warm as they otherwise might with summertime southwesterly flow ahead of a front, but there should be plenty of moisture to support heat indices over a hundred degrees in at least a few locations. As with other similar events so far this summer, this should be just below the criteria for a heat headline. Lenning && .LONG TERM... 303 PM CDT Tuesday through Sunday... High pressure builds back in midweek which should help to keep the majority of the area dry. Have held onto some low precip chances across our southern zones on Tuesday and Wednesday due to some remaining uncertainties with regard to where the cold front stalls out late Monday night. Depending on where the front ends up, the entire area could very well remain dry both days. The upper jet becomes more quasi-zonal with a couple subtle disturbances moving beneath the flow into the weekend. Models have trended drier through the extended thanks to surface high pressure and lack of strong forcing. However, due to variability the between model runs will hold on to occasional low precip chances most days. Any shower/thunderstorm development would probably be more diurnally driven. High temperatures are expected in the 80s each day, with cooler temps near the lake. Petr && .AVIATION... For the 00Z TAFs... Aviation forecast concerns: * Area of convection passing across northern Chicago suburbs early this evening - potentially near KDPA and KORD. * MVFR ceilings 2500-3000 ft likely for a time this evening, and possibly again Monday morning. * Additional potential periods of thunderstorms early Monday morning, and again mid-late afternoon into early evening. Cluster of thunderstorms continues to propagate eastward across southeast WI and far northern IL early this evening, in association with a remnant MCV/mid-level circulation. Atmosphere is generally weakly capped per RAP soundings, with convection expected to be focused in the vicinity of the MCV and any attendant outflow boundaries from current storms. Outflow has spread southeast into northern tier of IL counties, with additional scattered convection likely to continue to push east through the northern Chicago suburbs through about 9-10 pm. While current trajectory favors storms to pass north of KDPA and KORD, scattered development along the southern periphery could come close or clip these terminals. In addition, and area of MVFR ceilings in the 2500-3000 ft agl range have developed in the south winds across parts of north central and northeast IL, and may affect the terminals for a time this evening. Confidence in convective trends decreases past this evening, with various convective allowing models (CAMs) indicating an array of possible solutions from later tonight through Monday. There does seem to be general agreement in the development of additional showers and thunderstorms across parts of central IL after midnight tonight, in association with a mid-level short wave and a modest southwesterly low level jet. While the bulk of this activity would likely occur south of the terminals, several models do indicate isolated to scattered development across northern IL, while others depict significantly different development and evolution from the northwest. Confidence in any particular of these scenarios is rather low, and have maintained a prob30 mention for this potential for additional TS toward morning. Guidance is in a little better agreement in depicting the potential for additional MVFR ceiling development across the area early Monday, which may persist into late morning or midday before lifting to VFR. A third potential period of thunderstorm potential exists Monday afternoon and evening, though placement and extent will likely be highly dependent upon what occurs earlier in the morning. If no extensive convection develops early AM, the threat for a period of strong storms would be higher in the afternoon. For now will maintain a prob30 for this period as well, with confidence again fairly low on details pending what happens early Monday. Ratzer && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ Visit us at Follow us on Facebook, Twitter, and YouTube at:
National Weather Service Raleigh NC
931 PM EDT Sun Aug 9 2020 .SYNOPSIS... A weak surface trough will linger over the region through Monday as high pressure builds aloft. The high pressure aloft will weaken over the Carolinas by mid-week, allowing a new surface trough to develop to focus showers and thunderstorms. && .NEAR TERM /TONIGHT/... As of 931 PM Sunday... Convection is in the process of dissipating now with the sun having set. A few cells lingering over our SW Piedmont zones will soon dissipate, then look for the rest of the night to be partly cloudy and warm with lows in the upper 60s to lower 70s. The HRRR and NAM forecast soundings suggest some patchy fog and perhaps some stratus may form after 08Z tonight and linger through about 13Z before lifting. Coverage should be quite scattered and most likely where the heaviest rain fell today. && .SHORT TERM /MONDAY AND MONDAY NIGHT/... As of 400 PM Sunday... The remnants of an MCS currently over southern IL, southern IN, and western KY will reach NC tomorrow morning, which may enhance convection over our region tomorrow afternoon and evening. This combined with a forecast weakness in the upper ridge over the Southeast US and an uptick in shower and storm coverage in the CAM guidance mean POPs have been increased tomorrow to high chance (40- 50%) in the southern Piedmont, Sandhills, and southern Coastal Plain, which will be closest to the track of the MCV that looks to pass south of the region. Elsewhere, POPs are 25-40%. While widespread severe weather is not expected, a few strong wind gusts and locally heavy rain are possible, mainly in the south. High temperatures tomorrow will be similar to today`s and near normal (upper-80s to lower-90s) with lows Monday night again in the upper- 60s to lower-70s. && .LONG TERM /TUESDAY THROUGH SUNDAY/... As of 250 PM Sunday... Models indicate that a weakness(remnants of the MCV moving into the lower Ohio and Tn Valley)in the subtropical ridge will linger INVOF the SE US coast through at least Thursday. At the surface, the lee- side surface trough will persist while meandering over central NC. While the weak upper disturbance/PV anomaly near the SE US coast should become increasingly sheared with each passing day, it`s looking increasingly likely that this feature will serve to enhance what should otherwise be primarily diurnal rain chances through midweek, especially across eastern NC. By late week and through the weekend, Bermuda high pressure over the western Atlantic will retrograde westward over the Carolinas; while at the same time a series of mid-level shortwave troughs traversing the Mid-MS/OH Valleys will dampen/deamplify as the move east into the region. This will likely set up an increasingly active/stormy pattern over the Carolinas as a diffuse frontal boundary settles over the region. Seasonable temps through the period, with highs ranging from upper 80s to lower 90s and lows in the upper 60s to lower 70s. && .AVIATION /00Z MONDAY THROUGH SATURDAY/... As of 904 PM Sunday... Through 00Z Tuesday: Evening shower/tstm activity has mostly died down across most of central NC, with the exception of our SW Piedmont zones (east of KCLT). And the activity there too should wind down in the next hour or so, and should not be an issue for any of our TAF sites across central NC. Otherwise, look for VFR conditions at our TAF sites through 08Z, then some local fog and low clouds (and assoc IFR or LIFR flt conditions) will develop, but should occur particularly where the heaviest rain fell earlier today. So KRDU, KFAY, and KRWI will have the best chance to see said lower flt conditions Monday morning. KINT/KGSO should remain VFR all night. Once any low clouds and fog burn off after 13Z Monday, look for VFR conditions until the next round of afternoon/evening showers/tstms form Monday afternoon. After 00Z Tuesday: Scattered showers and storms are expected every afternoon and evening through the end of the period, with chances increasing as the week progresses. Brief drops to sub-VFR conditions are possible in any storms. Early-morning low stratus/fog are also possible each day through the end of the period, with chances of this also increasing by late in the week. Otherwise, VFR conditions will prevail. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Badgett NEAR SHORT TERM...Danco LONG TERM...CBL