Area Forecast Discussion
Issued by NWS Paducah, KY

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000 FXUS63 KPAH 190857 AFDPAH Area Forecast Discussion National Weather Service Paducah KY 357 AM CDT Mon Apr 19 2021 .SHORT TERM...(Today through Wednesday) Issued at 242 AM CDT Mon Apr 19 2021 At the time of this writing, all pcpn had gone, and the only low/mid clouds left were lingering over western KY, soon to dissipate, as a mid level shortwave continued to depart to the east. In its wake, moisture from generally light rains yesterday combined with light winds and clear skies to form patchy fog, some dense, across parts of the region. This tendency will continue until about 14Z. High surface pressure centered over the Gulf coast will nose up into the PAH forecast area today and tonight, keeping the region pcpn-free until essentially Tue afternoon (as depicted by most of the short range models). By then, clouds and rain showers are forecast to rapidly expand across most of the region from northwest to southeast. This will be due to a strong shortwave and surface cold front originating out of western Canada. Most of the pcpn will be post-frontal as a brisk wind shift makes its way through most of the region in the afternoon. The rest of the region, namely southwestern IN and most of western KY, will receive rainfall primarily in the evening. QPF to around a quarter inch is forecast. As the pcpn comes to an end Tue night, there may be some snowflakes in the air mainly north of the OH River. In addition, freezing temperatures are most likely over mainly parts of southeastern MO and southern IL. Thus, for now, a Freeze Watch will be issued for that area. Frost is possible everywhere after midnight, except southwestern IN and the Pennyrile region of KY, if the winds let up enough. Skies should be mostly clear over most of the region by near daybreak, which would tend to favor its development. Some record lows may be challenged. Expect highs Wed to be only in the lower to middle 50s with some clouds from time to time in the cyclonic flow aloft. .LONG TERM...(Wednesday night through Sunday) Issued at 242 AM CDT Mon Apr 19 2021 Surface high pressure will settle over the region Wednesday night, leading to calm conditions overnight. Aloft the last of the Great Lakes trough will rotate through the region and that according to the 00Z GFS could lead to a few more showers. That seems a bit extreme, but some continued cloud cover could mess up the radiational cooling and frost potential for Thursday morning. We will stick with clearing skies overnight and indicate significant frost over the entire region. Dewpoints are in the upper 20s, so there is potential for some areas to freeze again over northern portions of southern Illinois and southeast Missouri. With temperatures only expected to touch freezing for a brief while, the widespread frost will likely be the bigger concern for vegetation. Surface high pressure will dominate the region Thursday leading to sunshine and cool, dry conditions. Highs will be in the upper 50s to near 60, which is over 10 degrees below normal. For Thursday night through Saturday, there is quite a variety of solutions across our region. Most guidance brings an upper trough through Friday night into Saturday, but they differ in how well organized it is and how much QPF we may get. Guidance also differs in how soon any showers may reach southeast Missouri. The ECMWF has been consistently bringing some showers in southeast Missouri with an initial upper impulse Thursday night, but with such dry air in place, that seems a bit optimistic. On the flip side, the 00Z GFS keeps us dry, and with the surface high still in control, more frost would be possible at least across southwest Indiana and the Pennyrile, and possibly farther west as well. For now we will side with the ECMWF solution and keep any frost east of our region while 20-40% PoPs spread eastward across most of the region through the night. PoPs will remain the same through Friday, as south winds pick up to some extent, but the the main trough remains to the west. PoPs ramp up to likely levels Friday night as the upper trough approaches. There is a decent signal in most guidance for convection to blow up to our south, essentially robbing our area of the better low-level moisture return. If this occurs, our PoPs and QPF could be overdone. If the coherent trough and surface low of the 00Z ECMWF is right, QPF and PoPs will not be high enough. Could not find much instability in the deterministic guidance, so left it out for now, but would not rule it out Friday night. We will dry out Saturday night and remain dry through next Monday. Surface high pressure will dominate Sunday and then south winds will return Monday as upper-level ridging develops over the region. High temperatures will remain below normal Friday and Saturday and then climb to near normal Sunday. By next Monday we will climb above normal into the middle 70s. Lows will be well below normal Thursday night and then moderate closer to normal for Friday night through Sunday night. && .AVIATION... Issued at 1035 PM CDT Sun Apr 18 2021 Clouds will continue to clear out tonight, with winds becoming light. The guidance isn`t showing much in the way of fog. But it`s something to monitor given the clearing, earlier light rains and near calm winds through daybreak. Otherwise VFR, with winds becoming WSW 5 to 10 kts Monday. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...Freeze Watch from late Tuesday night through Wednesday morning for ILZ075>078-080>086-088. MO...Freeze Watch from late Tuesday night through Wednesday morning for MOZ076-086-087-100-107-108. IN...None. KY...None. && $$ SHORT TERM...DB LONG TERM...DRS AVIATION...CN

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