Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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057 FXUS63 KILX 160924 AFDILX Area Forecast Discussion National Weather Service Lincoln IL 424 AM CDT Sun Jun 16 2024 .KEY MESSAGES... - An extended heat wave is on tap this week across central and southeast IL, as hot and humid weather prevails. Heat index values will peak in the upper 90s to around 100 degrees this afternoon, and 100 to 105 degrees Monday afternoon. Afternoon heat indices are expected to be in the mid to upper 90s Tuesday through Saturday, and may reach back to around 100 late this week. - Isolated thunderstorms are possible through Saturday, mainly during the afternoon and early evening hours. Severe weather risk will be low this work week over the area, though lightning hazards and gusty winds will exist. && .DISCUSSION... Issued at 400 AM CDT Sun Jun 16 2024 Predawn surface map shows 1024 mb high pressure over the Adirondack and Catskill mountains of eastern NY state while a warm front was over northeast MO and eastern Iowa and extending to 995 mb low pressure over north central SD. A few MCS`s with clusters of showers and thunderstorms were over northeast KS, nw MO and central Iowa into eastern MN and central/western WI. This convection was lifting ne and mostly staying nw of IL, though clipping far nw Jo Daviess county. Some cirrus clouds over the IL river valley especially nw of the IL river, while rest of CWA is clear. Temperatures at 330 am ranged from mid 60s near the Indiana border/Wabash river to 70-75F from highway 51 west with our larger cities of Peoria and Springfield at 75F. The warm front is forecast to lift ne across central IL during this morning with SSE winds shifting south to SSW with its passage and a tropical air mass flowing into the area today. Strong upper level high strengthens further over the southeast states and ridging over the eastern parts of Ohio river valley and Great Lakes. A few of the CAM members like the HRRR and HiResW- ARW show isolated convection slipping nw parts of Knox and Stark counties early this morning (between 12-14Z) and continued slight chances there. The complex of storms over ne KS and nw MO lifts ne and the HRRR shows some of this convection affecting areas from the IL river nw late this afternoon and early evening. Introduced slight chance of convection nw of IL river from 4-8 pm for this possibility. Otherwise much of CWA will be dry today with breezy south to SSW winds bringing in a hot and humid air mass for this afternoon. Highs 92-96F today with dewpoints 65-70F giving peak heat indices in the upper 90s to around 100F. Airnow.gov has orange area (unhealthy for sensitive groups) today in the Wabash river valley). Air quality alerts are in effect east of IL over Indiana through this evening. Muggy lows tonight in the mid 70s with some lower 70s near the Indiana border. A 595 dm 500 mb high drifts northward over the mid Atlantic States on Monday with some deeper gulf moisture lifting into parts of central and especially east central and southeast IL by Monday afternoon. This to develop isolated showers/thunderstorms Monday afternoon with best chances near the Wabash river valley. Breezy south to SSW winds bring another hot and humid day with highs in the mid 90s and afternoon heat indices of 100-105F. This will be close to heat advisory criteria of 105F and heat headlines may eventually be needed for Monday afternoon plus depending on duration and intensity of this weeks heat wave. Heat watches have been posted in Ohio, eastern Indiana and southern half of lower MI Monday afternoon thru Friday. Isolated convection to diminish in southeast IL after sunset Monday evening. Muggy lows in the mid 70s Monday night across the CWA. The strong subtropical ridge builds over the mid Atlantic states and into New England on Tuesday and continues to stream moisture from the western gulf of Mexico into IL. Diurnally driven isolated convection expected again Tue afternoon and looks to be a bit more coverage over CWA on that day. More cumulus clouds Tue keeps temps a few degrees cooler than Monday with highs in the lower 90s and afternoon heat indices in mid to upper 90s, and near 100F nw of the IL river where more sunshine expected Tue. Lows Tue night in the low to mid 70s, with isolated convection dissipating around sunset. The 500 mb high strengthens to around 600 meters near NJ and southern New England coast by Wed/Thu while riding back into IL with 500 mb heights rising above 594 meters over CWA on Thu. Isolated convection chances on Wed afternoon appear to be more focused nw of I-55 and mainly nw of the IL river. Highs Wed 90-95F and mid 90s on Thu and Fri and peak heat indices of 95-100F and possibly getting above 100F on Thu and Fri. The strong upper level ridge back into IL to keep the frontal boundary nw of IL late this week along with better chances of convection. Extended models show the subtropical ridge still affecting central and southeast IL on Saturday and then retreating se on Sunday as a weak trof digs over the northern states. Still differences with models that far out on how this evolves but consensus has 20-30% pops arriving Sat afternoon and Sat night (highest pops northern CWA) and 30-40% pops next Sunday and temps starting to cool a few degrees over central IL. 07 && .AVIATION... (For the 06z TAFs through 06z Sunday Night) Issued at 1131 PM CDT Sat Jun 15 2024 Showers/storms west of the Mississippi River are expected to largely track northwest of KPIA early Sunday morning, but may be close enough to produce some brief ceilings around 5,000 feet there. Overall, VFR conditions will be the rule the next 24 hours. Winds turn southerly and increase to 10-15 knots early Sunday morning, and a few gusts near 20 knots or so can`t be ruled out. Winds should drop off around sunset. Geelhart && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$