606 FXUS63 KPAH 191008 AFDPAH Area Forecast Discussion National Weather Service Paducah KY 408 AM CST Sat Jan 19 2019 .SHORT TERM...(Today through Monday night) Issued at 400 AM CST Sat Jan 19 2019 Significant winter weather impacts are expected this afternoon into tonight as an area of low pressure moves by just to the south of the region. Until then, occasional rain showers are expected through the morning hours. Enough elevated instability exists for a continued small chance of thunder across the southern half of the area through the morning. While the heaviest rain has likely already occurred overnight, an additional one quarter to one half inch is possible through noon. Temperatures will begin to plummet below freezing this afternoon as Arctic air plunges southeast into the area on the west side of the low. At the same time, large scale forcing for lift enhances in the deformation zone to the northwest of the low's track. As a result, rain is expected to change to snow rapidly from northwest to southeast through the afternoon across most of the area. The transition may wait until early this evening across the Kentucky Pennyrile area. A very brief mix with sleet or freezing rain cannot be ruled out, but this event by and large looks to be mainly rain and snow. At this point, most of our forecast model suite indicates the likelihood of a period of moderate to occasionally heavy snow across most of the area. Locations along and either side of the Ohio River appear to stand the greatest potential of receiving frontogenetically forced heavier banded snow. In this region, hourly snowfall rates of 1 to 2 inches are possible. Even though the ground will be saturated from prior rains, it should not take that long for the snow to begin to accumulate as temperatures plunge below freezing. Most of the accumulation is expected during the late afternoon and evening hours. Current snowfall projections have 2 to 4 inches accumulating across most of the area. Slightly lesser amounts of 1 or 2 inches are possible north near Mt. Vernon, Illinois and south near the Tennessee border. The highest snow accumulation potential appears to be centered across the central part of our forecast area generally either side of the Ohio River. In this corridor, 3 to 6 inches is expected mainly east of Interstate 24 in southeast Illinois to the Evansville and Owensboro areas of southwest Indiana and northwest Kentucky. Locally higher totals cannot be ruled out where banding occurs. For this reason, we have upgraded to a Winter Storm Warning across southwest Indiana and portions of southeast Illinois and northwest Kentucky. Along with the heavy snow, very strong northwest winds of 20 to 30 mph with gusts as high as 40 to 45 mph are expected late this afternoon and this evening. This may create periods of near white- out conditions, especially in the heaviest snow bands. In conjunction with our neighboring offices to the north and east, decided not to issue a Wind Advisory and instead let the Winter Weather Advisory and Winter Storm Warning products highlight the entirety of the expected impacts. Even after the precipitation has come to an end, substantial travel impacts will likely linger into Sunday with lows tonight in the teens and highs on Sunday in the 20s. Not only will temperatures be cold enough to prevent road chemicals from working to their fullest potential, but road crews will likely not have much of a chance to pre-treat today ahead of the storm given the ongoing rain. This makes the potential for flash freezing and black ice a real concern as temperatures plunge below freezing later today and tonight. Wind chills in the single digits are also expected across the entire region late tonight into Sunday morning. The good news is that some moderation in temperatures is expected by Monday as highs attempt to climb back into the 30s. That may be slowed some though depending on how much snow cover is on the ground by then. Dry conditions should prevail Sunday through Monday night with high pressure in control. .LONG TERM...(Tuesday through Friday) Issued at 400 AM CST Sat Jan 19 2019 There is reasonable forecast confidence for Tuesday into Wednesday, but it decreases significantly Thursday into next weekend. We will be dropping back into a cold stretch after the mid-week system, but how cold and whether there will be any snow are the main questions. We will start out with an upper-level ridge along the Appalachians, with troughing from western Ontario southwest through the southern Rockies. A piece of this trough will lift northeast in a positive- tilt fashion through the central Plains Tuesday and to the Great Lakes by Wednesday morning. This will result in fairly strong warm advection across our region Tuesday, and a cold frontal passage late Tuesday night into Wednesday. How much push there is behind the front will determine how quickly we will dry out from northwest to southeast. The best guess at this point is that we will begin to dry out in the northwest Wednesday morning, but the precipitation may persist at least over west Kentucky into Wednesday night, before coming to an end as the remaining portion of the southwest upper trough pushes eastward through the region. The precipitation will start out as rain Tuesday morning over southeast Missouri and overspread the entire area through the day. The heaviest rains are expected Tuesday night, when 1/2"-3/4" QPF will be possible. The consensus of 00Z guidance has temperatures falling through the day Wednesday, and this will likely result in a change over to some light snow before the precipitation comes to an end. If the precipitation lingers longer it would likely be the result of a lesser push and temperatures would be slower to fall, so we may overdone, but we do have some accumulations in the forecast Wednesday. Generally a half inch or less with some potential for an inch or more over the Pennyrile if the cold air catches up the better precipitation. Not a very confident forecast scenario at this time. The remaining portion of the upper trough will push east of the area on Thursday and get absorbed into a massive/deep upper trough that will cover everywhere east from the Rockies. There will likely be a surge of Arctic air at some point Friday or Saturday, but trying to time individual impulses in this fast cyclonic flow will be difficult for the models, and believing the details of any associated QPF even more difficult. The bottom line is it will be quite cold as we head into next weekend, and a period or two of snow will be possible, but the details are just too difficult to call at this point. && .AVIATION... Issued at 1037 PM CST Fri Jan 18 2019 Conditions will continue to deteriorate. Expect numerous showers and scattered thunderstorms overnight with conditions becoming mainly IFR, possibly LIFR. Saturday late morning, a cold front will pass through, and shift SE/E winds around to the north, increasing to 15-25kts. Off and on rain with mainly IFR conditions will persist. Saturday afternoon through sunset, precipitation will change to snow. Winds will continue to increase, with north winds possibly gusting 30 to 35+ kts. The snows should diminish rapidly from west to east from 02z-05z. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...Winter Weather Advisory from noon today to midnight CST tonight for ILZ075>078-080>082-084-085-088-089-092>094. Winter Storm Warning from noon today to midnight CST tonight for ILZ083-086-087-090-091. MO...Winter Weather Advisory from noon today to midnight CST tonight for MOZ076-086-087-100-107>112-114. IN...Winter Storm Warning from noon today to midnight CST tonight for INZ081-082-085>088. KY...Winter Weather Advisory from noon today to midnight CST tonight for KYZ001>006-008-009-011>013-016-017-021-022. Winter Storm Warning from noon today to midnight CST tonight for KYZ007-010-014-015-018>020. && $$ SHORT TERM...RJP LONG TERM...DRS