Area Forecast Discussion
Issued by NWS Chicago, IL
Issued by NWS Chicago, IL
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208 FXUS63 KLOT 032009 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 309 PM CDT Mon Jun 3 2024 .KEY MESSAGES... - Isolated showers and storms across northern Illinois into this evening. - Unsettled weather pattern continues through mid-week as showers and storms are expected Tuesday into Wednesday morning. - Warm, moist air continues to bring the warmer temperatures across northern Illinois Tuesday, but cooler temperatures are expected Thursday and Friday behind frontal passage. && .DISCUSSION... Issued at 309 PM CDT Mon Jun 3 2024 Showers and storms have developed this afternoon across northwestern Illinois, as a north-south oriented boundary sits along the mid and upper Mississippi River Valley. Additional development is expected to occur this afternoon through the evening, however it is expected to remain near and west of the I-39 corridor over the next hour or 2, before beginning to shift ne across northern counties of the LOT CWA...north of roughly the I-88 corridor and then I-90 corridor heading into the overnight. Isolated strong to severe storms are possible, however most of the activity is forecast to remain general showers and storms. Heading into the overnight and Tuesday, a low pressure system will deepen across the southern Plains before moving into the Ohio River Valley late Tuesday into early Wednesday. This will lift moisture from the Gulf into the area Tuesday morning into the afternoon, bringing another chance for shower and storm development as instability once again increases across the Midwest. With warm southerly air flowing into the region ahead of this system, expecting showers and storms to rapidly develop Tuesday afternoon (20-22z) and track eastward through evening. A larger upper-level low pressure core situated across central Canada will track eastward Tuesday, trailing an elongated frontal boundary into the central Plains and deep south. As this boundary tracks to the east Tuesday night into Wednesday morning, the chance for a second round of showers and storms will move through the region. The question at hand today was timing of this frontal system, as well as the early convection Tuesday afternoon, this is expected to keep the potential of strong to severe storms at bay overnight Tuesday into Wednesday. Drier weather is forecast to return across the Midwest, as the unsettled weather pattern is finally shifted out of the region during Wednesday. Along with the dry weather arriving Thursday and Friday, models are indicating a break in the summer-like temperatures with highs back in the 70s. The 70s then look to linger into and through the upcoming weekend across much of the area, with some cooler temperatures expected near and along the lakeshore. Chances this weekend for isolated to scattered showers and storms at times could be possible this weekend, however the overall probability remains less than 25% at this time. Baker && .AVIATION /18Z TAFS THROUGH 00Z WEDNESDAY/... Issued at 1242 PM CDT Mon Jun 3 2024 Key Aviation Impacts for the current TAF period: - Non-zero thunder chances tonight, but confidence was low enough to remove from the TAF - Winds are expected to be prevailing 190, but occasional flopping to 170 is possible through Tuesday late morning - Leading showers may arrive at Chicago terminals late Tuesday afternoon Winds are slowly becoming more prevailing southwesterly; however, some flip flopping to southeasterly is still possible through the early afternoon. While there are storms just north of KRFD moving to the northeast at the time this discussion was published, the biggest change to the forecast was removing thunder from the TAFs. There will still be enough instability to generate a pop-up storm or two later today, latest guidance keeps the best areas for storms well north of terminals. With the probability less than 30 percent, it was decided to pull the thunder from the TAF and monitor chances through the night. There is low confidence in the exact wind direction overnight (SE vs. SW), though gusts are expected to come down before returning Tuesday afternoon. The next system that will bring showers and storms to the region will likely arrive after 00Z (and therefore outside the current TAF window). However, latest high-res guidance suggests a weak boundary drifting northward in the afternoon. Instability does not look impressive to add thunder, and while timing may be pushed back in later TAF packages, felt comfortable introducing -SHRA into the ORD/MDW TAFs. DK && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ Visit us at weather.gov/chicago