Area Forecast Discussion
Issued by NWS Paducah, KY
Issued by NWS Paducah, KY
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489 FXUS63 KPAH 250835 AFDPAH Area Forecast Discussion National Weather Service Paducah KY 335 AM CDT Wed Sep 25 2024 .KEY MESSAGES... - A few showers or storms will be possible over the southern half of the Quad State this afternoon. Then dry weather is expected tonight, and possibly through the day Thursday. - Chances for widespread heavy rain will ramp up Thursday night through Sunday, as the remnants of Tropical Storm Helene interact with an upper-level storm system. - The heaviest rain is expected from late Thursday night through Friday evening. Forecast rainfall in this period currently ranges from around 2 inches along I-64 to 3.5 inches in far southern portions of the region. The rains will become lighter and more isolated through the weekend. - The Quad State will begin to dry out on Tuesday as a cold front passes. Cool, fall-like conditions are forecast for next Wednesday. && .DISCUSSION... Issued at 335 AM CDT Wed Sep 25 2024 An upper low will move south through the Quad State today, as surface high pressure builds in. With remnant low-level moisture and the cold pool aloft associated with the upper low, widely scattered showers and thunderstorms will be possible over the southern half of the region this afternoon. As is the case with any convection under upper lows, some cold air funnels cannot be ruled out this afternoon. No severe weather is expected. Brief heavy downpours, and lightning will be the primary concerns. Tonight should be dry throughout the Quad State, and guidance has trended slower with the onset of rains with the approach of the remnants of Tropical Storm Helene. Much of the region will be dry through Thursday morning, and possibly the afternoon, especially over southeast Missouri and southern Illinois. The upper low will drift south or southwest to a position somewhere between Memphis and Little Rock on Thursday, as Helene makes landfall in northern Florida. These two systems will then begin to dance with Helene heading north through Georgia and eventually northwest toward the Quad State. Current guidance has the two systems totally merged somewhere in our vicinity by Saturday morning. Confidence in the details of this interaction is still quite low, as this is a rare occurrence and the models are not likely to get it right this far out, especially with how fast this occurs (from landfall to merger in 48 hours). WPC QPF has storm total rainfall through Sunday ranging from 2.5" along I-64 to 3.5-4" over the southern half of the region. The bulk of this rainfall is expected in the 24 hour period from late Thursday night through Friday evening. The 00Z GEFS and ECENS are not very bullish for this magnitude of rainfall. They indicate no more than a 50% chance of reaching 2" in this 24 hour period over far southern portions of the region, and little to no chance of reaching 2" over the northern half of the region. The ensemble SA tables indicate highly anomalous moisture at 500mb, but have minimal positive anomalies in the low-levels. It is highly likely that Helene will suffer mightily crossing the southern Appalachians on its way here. This should severely weaken the low-level circulation/winds and much of the tropical moisture is likely to be rained out on the east side of the mountains. NBM surface dewpoints never get any higher than the middle 60s across the Quad State which is not exactly tropical (we had dewpoints in the lower 70s just last weekend). All of this is evidence for taking the current QPF with a grain of salt, and tempering expectations. In general, the heaviest rains should be over west Kentucky with the lightest amounts in the far northwest portions of the Quad State. In other news, the 00Z ECENS has a 50% chance of 35kt wind gusts over the northern half of the region Friday afternoon and evening. Given the concern for the weakening of the system as it comes through the Appalachians, it would seem unlikely we will see gusts this strong, but confidence in the merging of the two systems is low, so it bears watching the trends over the coming days. Regardless of the intensity, the strongest winds will be Friday afternoon and evening, which in addition to the wet conditions expected, will make for some challenging conditions for Friday night football games and any other outdoor activities. At least at this time, the NBM does not have any lightning forecast Friday afternoon or evening. As the merged storm system spins down over the region this weekend, showers will become more scattered with the greatest coverage each afternoon. The coverage and intensity will both decrease for Sunday and moreso on Monday. The consensus of guidance now has the system east of the area by Tuesday, with northwest flow aloft over our region. This will bring a surge of cool surface high pressure through the Quad State Tuesday. High temperatures next Wednesday will be rather fall-like in the upper 60s to lower 70s, and there will be a healthy north breeze. && .AVIATION /00Z TAFS THROUGH 00Z THURSDAY/... Issued at 522 PM CDT Tue Sep 24 2024 Dew points have fallen into the lower 60s at the TAF sites after a cold fropa. Bases are SCT-BKN VFR, but patchy fog/low cloud may offer restrictions late tonight. Diurnal cu tmrw will rise into low VFR with daytime heating CIGS potential. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...None. MO...None. IN...None. KY...None. && $$ DISCUSSION...DRS AVIATION...