Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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099 FXUS63 KILX 161737 AFDILX Area Forecast Discussion...Updated Aviation National Weather Service Lincoln IL 1237 PM CDT Sun Jun 16 2024 .KEY MESSAGES... - A cluster of thunderstorms will develop and track across locations along/northwest of a Macomb to Minonk line this afternoon. Gusty winds and heavy downpours will be possible. - Seasonably hot and humid weather is on tap this week. Heat index values will peak at or above 100 degrees both this afternoon and Monday afternoon before readings settle back into the middle to upper 90s for the remainder of the week. && .UPDATE... Issued at 940 AM CDT Sun Jun 16 2024 14z/9am satellite/radar mosaic shows a Mesoscale Convective Vortex (MCV) over northern Missouri moving northeastward at about 30-35mph. Based on timing tools, this feature will skirt through the NW KILX CWA by mid to late afternoon. Most 12z CAMs suggest renewed convective development along/ahead of this feature...primarily along/north of a Macomb to Minonk line between 19z/2pm and 01z/8pm. As surface dewpoints climb into the upper 60s/lower 70s, SBCAPEs will increase to around 3000J/kg this afternoon: however, deep-layer shear will remain meager with 0-6km bulk shear values of only around 20kt. Think severe weather risk will remain low, with the main concerns being gusty winds and heavy downpours. Have updated the forecast to add slight chance PoPs as far south as a Canton to Normal line...with high chance PoPs focused from the Peoria area northward. Elsewhere around central Illinois, it will be a breezy and hot day. High temperatures will top out in the lower to middle 90s as heat index values climb toward 100 degrees. The heat will be somewhat mitigated by a southwesterly breeze at 10-15mph with gusts of 20-25mph. Barnes && .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 18z TAFs through 18z Monday Afternoon) Issued at 1237 PM CDT Sun Jun 16 2024 Clusters of thunderstorms currently over northeast Missouri/southeast Iowa will track northeastward this afternoon. While most of this activity will remain northwest of the central Illinois terminals, it will come close enough to justify VCTS at KPIA between 20z and 00z. Once the storms pass, dry weather is expected for the remainder of the 18z TAF period. Winds will be SW at 10-15kt with gusts of 20-25kt this afternoon, then the gusts will subside and sustained SW winds of around 10kt will continue through the night. Gusty SW winds will resume by mid-morning Monday. Barnes && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$