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Area Forecast Discussion
Issued by NWS Paducah, KY
Issued by NWS Paducah, KY
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148 FXUS63 KPAH 152348 AFDPAH Area Forecast Discussion National Weather Service Paducah KY 648 PM CDT Mon Jul 15 2024 .KEY MESSAGES... - A Heat Advisory remains in effect until Tuesday evening as peak heat index values between 105-110 degrees are expected. - Unsettled weather returns on Tuesday as a cold front slowly moves towards the region. The greatest risk is from late Tuesday into Wednesday when multiple rounds of showers and thunderstorms are possible. A Flood Watch is now in effect Tuesday evening into Wednesday morning across portions of southern Illinois and southwest Indiana. - High pressure will provide relief from the heat and humidity beginning Thursday through Sunday. && .UPDATE... Issued at 646 PM CDT Mon Jul 15 2024 Updated aviation discussion for 00Z TAFs. && .DISCUSSION... Issued at 328 PM CDT Mon Jul 15 2024 The heat and humidity remains the primary concern in the short term as dewpoints once again are running above model guidance in the mid 70s to near 80 degrees. This translates to a heat index between 105 to 110 degrees this afternoon and again on Tuesday. A Heat Advisory remains in effect until 01z Wednesday with maxTs progged in the low to mid 90s. Overnight minTs will also be a bit warm tonight in the mid 70s. Otherwise, scattered CU has once again developed this afternoon as a 500 mb ridge of high pressure remains located over the SW CONUS. A period of unsettled weather begins to arrive on Tuesday as a leading 500 mb shortwave downstream from a trough ejecting out of Canada provides forcing for ascent. The latest CAMs show a MCS developing south of the one that will move through the Chicago area later this evening. The general idea is for a decaying MCS to move towards the I-64 corridor early Tuesday morning, but forecast confidence is low on the spatial coverage of any pcpn. The parameters do not look terribly concerning should thunderstorms occur. Have limit PoPs to a 30-35% with blends of NBM and CONSShort given the uncertainty. One implication the morning convection will likely have is where a residual outflow boundary sets up, as this will be the main focus for the heavy rainfall potential Tuesday night. It is worth noting any convection during the day Tuesday could also provide some relief from the heat up north. Have leaned closer to the NBM 25th percentile due to the possibility of more cloud cover. As a cold front slowly sags southeast Tuesday evening, shower and thunderstorm coverage becomes more likely from northwest to southeast as a baroclinic zone sets up. The RAP13 shows 3000-4000 J/kg of MLCAPE and limited effective bulk shear around 25 kts 00z Wednesday. Given a theta-e difference of 25 degrees and 0-3 km lapse rates around 7.0 C/km, there remains a marginal risk in SPCs D2 outlook for a few isolated gusty severe storms capable of producing downburst across northern portions of the CWA late Tuesday afternoon into Tuesday evening. However, instability quickly wanes with the loss of diurnal heating as a transition to a heavy rain risk remains the main concern Tuesday night. The 12z HREF PMM and latest 18z HRRR both show locally up to 2-4+ inches setting up right along the I-64 corridor across portions of southern Illinois and southwest Indiana where training convection is becoming probable. There are still some model differences in the exact placement as the aformentioned outflow boundary will play a big role, but overall confidence is increasing in the potential for heavy rainfall to occur across portions of the FA. PWATs remain progged around 2.00 inches with a light LCL-EL cloud layer mean wind around 15 kts south of the boundary. This favors the potential for multiple thunderstorms that will be capable of producing torrential downpours. For this reason, have gone ahead and issued a Flood Watch from 00z Tuesday evening until 12z Wednesday morning. Across the rest of the FA, up to 1-2 inches of rainfall remains possible as additional rounds of showers and thunderstorms push south Wednesday into Wednesday night. By Thursday morning, the cold front will eventually push south of the FA, allowing for dry air to filter in across the FA from the northeast as sfc high pressure builds into the lower Ohio Valley. MaxTs are progged only in the low 80s by the NBM Thursday and Friday with minTs ranging from the upper 50s to lower 60s Thursday night. Dewpoints around 60 degrees will certainly make this airmass quite refreshing! Temps do gradually moderate over the weekend as a 500 mb trough digs across the central Plains, but look to still remain slightly below normal. As a disturbance approaches from the south, daily shower and storm chances gradually increase by Sunday as the following week looks to start off a bit more unsettled. && .AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/... Issued at 646 PM CDT Mon Jul 15 2024 VFR conditions are anticipated through much of Tuesday. Remnants of overnight convection to the north of the area will pose the potential for scattered showers and thunderstorms across northern reaches of the area late tonight into Tuesday morning, impacting mainly KMVN and KEVV. Scattered thunderstorm development is also possible late Tuesday afternoon into Tuesday evening across the entire region. Southwest winds 5 to 8 knots will increase to 10 knots by late morning and afternoon on Tuesday. Some gusts to 15 knots are also expected. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...Heat Advisory until 8 PM CDT Tuesday for ILZ075>078-080>094. Flood Watch from Tuesday evening through Wednesday morning for ILZ075>078-081>083. MO...Heat Advisory until 8 PM CDT Tuesday for MOZ076-086-087-100- 107>112-114. IN...Heat Advisory until 8 PM CDT /9 PM EDT/ Tuesday for INZ081-082- 085>088. Flood Watch from Tuesday evening through Wednesday morning for INZ081-082-085>088. KY...Heat Advisory until 8 PM CDT Tuesday for KYZ001>022. && $$ UPDATE...RJP DISCUSSION...DW AVIATION...RJP