Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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784 FXUS63 KILX 120834 AFDILX Area Forecast Discussion National Weather Service Lincoln IL 334 AM CDT Wed Jun 12 2024 .KEY MESSAGES... - Unseasonably warm temperatures arrive today. - A prolonged period of hot and humid conditions begins Thursday and continues into next week. Air temperatures will range from the upper 80s to middle 90s with heat indices approaching 100 Sunday onward, posing a threat for heat-related illnesses. - Shower and storm chances (30-50%) return late Thursday afternoon into evening. Some of these storms could become severe with damaging winds and large hail. && .DISCUSSION... Issued at 332 AM CDT Wed Jun 12 2024 Water vapor imagery early this morning shows an upper trough working through Ontario Canada with a surface trough extending south from there into the Great Lakes Region. Mid-level moisture tied to this feature and another upper wave over the southern Plains has allowed some mid-level clouds to pass through the area overnight. Gentle southerly flow on the western fringes of surface ridging has been advecting milder air northward with 3 am temperatures ranging from the upper 60s across our west to upper 50s in the east where lower dewpoints are. Upper ridging over the southwest US will build eastward today, allowing mid to upper heights to rise throughout the day and putting a start to a prolonged period of heat. A potent upper shortwave will dive toward the northern Plains states late tonight, then track across the northern Great Lakes Region on Thursday. A cold front will extend southward from its associated surface low and approach from the northwest going into Thursday night. Thunderstorms will develop from the Dakotas into western Wisconsin late tonight with the remnants of that activity entering northern Illinois early Thursday morning. Most CAMs have this fading out prior to reaching us, but can`t rule out a stray shower or storm around or just before sunrise Thursday. Things turn hot and humid by Thursday as WAA ramps up and dewpoints approach the middle to upper 60s. High temperatures will approach or exceed 90 degrees with heat indices nearing 100 in spots (mainly west of I-55 where the highest dewpoints will be). Most guidance has instability reaching moderately strong values (~3000 J/kg MLCAPE) by Thursday afternoon with about 100-200 J/kg of CIN. Upper jet support will be somewhat displaced to our north, though deep layer shear of 40-45 kts will be more than enough to sustain any storms that become organized. CAMs show storms developing over eastern Iowa/northern Illinois late Thursday afternoon, then dropping south into central Illinois by early evening as the CAP erodes. Some of these storms could become strong to severe, posing a threat for damaging winds and large hail. Climatologically high PWATs around 2 inches would suggest any storms that develop will be efficient rainfall producers, though there is only a marginal threat for flooding due to antecedent dry conditions and the overall fast progression of the front. The threat for severe storms should lessen around or shortly after midnight as instability rapidly wanes. Somewhat drier air filters in behind the front as flow aloft becomes northwesterly. This will result in a brief "break" from the humidity on both Friday and Saturday before an amplified western US ridge shifts east, turning flow southwest aloft. Air temperatures on Friday and Saturday will peak in the middle to upper 80s with values bouncing right back into the 90s by Sunday. Dewpoints will climb into the upper 60s from Sunday onward, sending heat indices into the upper 90s to near 100 through much of next week. The threat for heat- related illnesses will be elevated during this time, especially due to the duration of the heat and limited relief at night. NMA && .AVIATION... (For the 06z TAFs through 06z Wednesday Night) Issued at 1029 PM CDT Tue Jun 11 2024 VFR conditions will prevail through the entire 06z TAF period. A couple bands of mid/high clouds will pass through the region through the pre-dawn hours of Wednesday, followed by mostly clear skies by sunrise. NAM forecast soundings and Cu-rule suggest SCT to perhaps BKN diurnal Cu with bases of 5000-6000ft during the afternoon. After that, skies will once again become mostly clear by evening. Winds will initially be S at less than 10kt, then will veer to SW at 10-15kt from mid-morning through the afternoon. Barnes && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$