Area Forecast Discussion
Issued by NWS Chicago, IL
Issued by NWS Chicago, IL
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153 FXUS63 KLOT 170941 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 441 AM CDT Mon Jun 17 2024 .KEY MESSAGES... - Hot and muggy conditions will prevail through the end of the week. Periodic chances for thunderstorms will continue, though many hours will remain dry. && .DISCUSSION... Issued at 238 AM CDT Mon Jun 17 2024 Through Tuesday Night: Today will be another warm day as a sprawling ridge begins to build across the Mid Atlantic. 850-500 mb thicknesses will increase a bit over where they were on Sunday, so temperatures may end up warmer by a few degrees. A glance at forecast soundings shows a little in the way of drying in the mid-levels, so it seems like dewpoints may mix out a bit more. Favored the warmest guidance for high temperatures today given the expected strong and deep PBL mixing with highs in the urban Chicago core near 96-98 degrees. With dewpoints largely expected to mix out into the mid 60s, heat indices look to be in the 95-105 degree range, with values at the higher end of that range more limited in coverage. We`ll be uncapped by midday in most locations given the forecasted temperatures and dewpoints. However, there don`t seem to be any well-defined impulses to drive notable large scale forcing for ascent in the region this afternoon. There is perhaps a low- amplitude disturbance visible in moisture channel loops across central Missouri which will lift northeastward today but that looks to be about it with the remnant convective vortex from Sunday expected to push east across Lake Erie. Slight chance (15-20%) PoPs look reasonable for this afternoon with any activity expected to remain few and far between. An isolated strong/gusty downburst wind threat can`t be ruled out given how hot and deeply mixed it`ll be. Tonight, a plume of deeper moisture emanating from the central and western Gulf of Mexico will surge northward. Mid-level lapse rates will trend towards moist adiabatic which will lessen the amount of instability available, but several embedded disturbances/vort lobes within the plume may be enough to crank out some showers or a few storms and have added some low precip chances to account for this. While the core of the moist plume will pivot east of us through Tuesday, overall increased tropospheric moisture looks like it might limit mixing a bit compared to Monday. With thickness values at or even a bit under Monday`s levels, air temperatures are expected to come down a few degrees although dewpoints may not drop as significantly. All of this nets peak heat indices Tuesday afternoon in the 95-100 degree range. Additional very isolated showers or storms once again can`t be ruled out with peak heating. Carlaw Wednesday through Sunday: Hot and humid conditions will continue to be the primary focus through the end of the week and into the weekend as a broad ridge and high pressure system over the eastern CONUS continues to build and remain stagnant. Southwesterly flow will allow temperatures to routinely be in the low-to-mid 90s Wednesday through Saturday. Dew points in the upper 60s will bring heat indices into the upper 90s with some areas occasionally pushing 100 degrees. This will keep us below Heat Advisory criteria (>105 degrees for a single day or >100 degrees for 4+ days), however, caution should still be exercised during long periods of time outdoors by taking breaks and hydrating. Overnight lows won`t bring much relief as temperatures are only expected to drop into the low- to-mid 70s due to the high moisture content. Although the heat is the main story through the extended, there are several chances for showers/storms. A synoptic cold/stationary front will be situated across Wisconsin on Wednesday. Convection will initiate ahead of this front and may sneak into the northwest portion of the CWA Wednesday afternoon, so have left some chance PoPs in the forecast. On Thursday, this front will move further southeast, potentially reaching the northern periphery of the CWA bringing another chance for showers and storms to the northwestern CWA. There is also a signal in the long range models for the front to push down Lake Michigan and enhance a lake breeze Thursday afternoon, setting the stage for a possible backdoor cold front scenario. Depending on the timing of this front, areas near the lakeshore may see an early high temperature with cooling temperatures through the afternoon, however, confidence in occurrence and timing is low at this time. Towards the end of the work week, the ridge will begin to flatten out and be pushed south by a trough moving across Canada bringing zonal flow to the area. Ensemble guidance shows a consistent signal for a shortwave to move across the area sometime this weekend, with a surface cold front bringing an end to this extended period of heat and humidity. This will also bring a chance for showers and storms with the passing of this front, however, confidence is very low on the timing. Carothers && .AVIATION /06Z TAFS THROUGH 12Z TUESDAY/... Issued at 1221 AM CDT Mon Jun 17 2024 Current satellite imagery shows a MCV moving away from the area and into Michigan. Some mid-level clouds associated with this MCV will stick around overnight, but VFR conditions are expected to persist. Tomorrow looks generally quiet with the exception of some gusty (around 25 kts) southwest winds in the afternoon. Mid-level moisture will allow some diurnal low-to-mid level clouds to develop tomorrow afternoon. A few of the CAMs hint at the possibility of some isolated storms tomorrow, but confidence in this actually occurring is too low to include in the TAFs. Carothers && .CLIMATE... Issued at 441 AM CDT Mon Jun 17 2024 Several temperature records will be threatened over the next few days. The records that appear to be in greatest jeopardy are today`s (June 17) record high for Chicago and several record warmest low temperatures for both Chicago and Rockford through Saturday, June 22nd. Here are the daily high and warmest low temperature records for Chicago and Rockford for each day through June 22nd: Chicago -------------------------------------------- Day: 6/17 6/18 6/19 6/20 6/21 6/22 -------------------------------------------- Record High: 96 98 102 104 101 97 Record Warm Low: 78 77 78 78 74 76 Rockford -------------------------------------------- Day: 6/17 6/18 6/19 6/20 6/21 6/22 -------------------------------------------- Record High: 99 99 99 101 100 97 Record Warm Low: 75 74 76 73 71 73 Ogorek && .LOT WATCHES/WARNINGS/ADVISORIES... IL...Air Quality Alert until midnight CDT tonight for ILZ005-ILZ006- ILZ012-ILZ013-ILZ020-ILZ021-ILZ103-ILZ104-ILZ105-ILZ106- ILZ107-ILZ108. IN...None. LM...None. && $$ Visit us at weather.gov/chicago