Scientific Forecaster Discussion
000 FXUS63 KPAH 182212 AFDPAH Area Forecast Discussion National Weather Service Paducah KY 512 PM CDT Thu Jul 18 2019 .UPDATE... Issued at 508 PM CDT Thu Jul 18 2019 Updated Aviation discussion for 00Z TAF Issuance. && .SHORT TERM...(Tonight through Saturday night) Issued at 255 PM CDT Thu Jul 18 2019 We are planning to keep the Excessive Heat Warning going as is through Sunday. The cloud cover associated with the mid-level disturbance over the region today has held temperatures down for much of the day, but other than west Kentucky most of the area has heat indices back above 100 and a lot of places will still likely get to 105. Briefly considered pulling west Kentucky back to a Heat Advisory, but with Friday expected to have the worst conditions throughout the area, decided to keep the Warning going to not confuse the public. Some convection has developed ahead of the MCV just south of our border into northwest Tennessee, and figure most of it will stay down there, but will keep a slight chance for a few more hours along the KY/TN border just to be safe. No guidance has been able to keep up with the upper 70 and lower 80 dewpoints across southeast Missouri and southern Illinois, so tried to stay a bit above the consensus at least for tomorrow. Also, temperature guidance continues to advertise middle 90s for tomorrow, but that seems a bit far-fetched given the extremely high dewpoints. Also, even areas to our northwest that had sunshine for most of the day are struggling to get into the lower 90s this afternoon. The bottom-line is that confidence in the details is not great, but with more sunshine expected Friday, it will feel disgusting over most of the region with max afternoon heat indices in the 103-108 range. Guidance is trending a bit cooler, more into the lower 90s, for Saturday, and the GFS even tries to bring some convection up into west Kentucky. Once again guidance is not likely high enough with dewpoints, so that may offset the slightly lower temperatures. Forecast max afternoon heat indices will be 102-107 over most of the region. .LONG TERM...(Sunday through Thursday) Issued at 255 PM CDT Thu Jul 18 2019 Models bring a cold front into northern portions of the PAH forecast area by 00z Monday, moving it through our region Sunday night. Scattered showers and thunderstorms will develop along the front Sunday, with the best chances Sunday afternoon into Sunday night, tapering off from north to south Monday. Kept pops in the chance category at best for our region for now. Conditions will remain hot and muggy Sunday, with highs in the lower 90s. Heat indices will be a couple of degrees lower than Saturday due to cloud cover, but with dew points in the middle 70s, heat index readings should still reach above 100 degrees across the area, with most locations still reaching around 105 degrees. Behind the front, surface high pressure will build over the middle and upper Mississippi river valley, and much cooler and less humid air will filter into the PAH forecast area. Afternoon highs in the lower to middle 80s, and dew points dropping in the upper 50s to lower 60s by Tuesday will result in very comfortable conditions for late July. Temperatures will moderate gradually by Thursday, but highs will still be a few degrees below normal and dew points will remain in the lower 60s. && .AVIATION... Issued at 508 PM CDT Thu Jul 18 2019 Convective debris cloud may impact terminals early this evening, otherwise generally VFR flight conditions are anticipated. The exception would be any late night restrictions in fog, which could knock vsbys down. However, guidance does not suggest this will be the case, with some gradient for light southerlies precluding its formation in the otherwise favorable moist environ. Tmrw should be another dry/hot day with MVFR bases developing with daytime heating. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...Excessive Heat Warning until 7 PM CDT Sunday for ILZ075>078- 080>094. MO...Excessive Heat Warning until 7 PM CDT Sunday for MOZ076-086-087- 100-107>112-114. IN...Excessive Heat Warning until 7 PM CDT Sunday for INZ081-082- 085>088.