294 FXUS63 KPAH 100927 AFDPAH Area Forecast Discussion National Weather Service Paducah KY 327 AM CST Sun Nov 10 2019 .SHORT TERM...(Today through Tuesday night) Issued at 327 AM CST Sun Nov 10 2019 Upper air flow pattern remains NW across much of the CONUS about a vortex over Hudson Bay, and a cut off low off the southern CA coast. High pressure was south of the area with a frontal boundary still well to our north. Thinking for today is the same. With high pressure to our south, allowing for low trop SSW flow and WAA, it will be mild, with highs into the lower to mid 60s, possibly upper 60s over parts of SEMO in the Ozarks region. It should be a mostly sunny day. The models at 6 p.m. this evening have the front at our door step (SEMO, SW IL). By 12z Monday, the front should extend from just NW of KEVV to KUNO. Strong 1048 MB high will be over the northern Rockies with a digging upper trof across the northern Plains and Upper Midwest. Late tonight, there is just a slight chance of rain into SEMO and southern IL. Through the day Monday, the upper trof will continue southeast, with the frontal boundary to about the Ohio River. Forcing and increased deep moist advection will result in rains developing through the morning, spreading east through midday. Monday afternoon, temperatures will begin to plummet as gusty NNW winds take over behind the front. Moisture will continue to advect ENE over the deepening layer of cold air pushing SE across the area. We expect rain across the area to change to snow in the afternoon across SEMO, southern IL and eventually southwest IN. The rain, snow transition line should be to about the Ohio by 5-6 p.m. with rain changing to snow in the evening over the rest of west KY. There may be an hour or so of mixed precipitation in the transition. But for clarity sake in the forecast, not too worried about that element. Nearly all of the wintry evening precipitation will be out of west KY by midnight. The models have been pretty consistent showing decent 700-300mb moisture (and in the -12 to -18C layer), phasing with existing abundant 1000-700mb moisture in the afternoon right over our CWFA, supportive of the transition to snow. If you just go with snowfall potential, taking out of the equation antecedent surface/road temps, areas east of the MS River could see up to 1 inch of accumulation, based on a slight uptick in overall QPF, and mean projections from an ensemble suite using the EC, HiRes data and GFS. Amounts may be slightly lower in SEMO toward the Bootheel region. The latest GFS/EC and CMC showed an uptick in QPF into the evening hours, primarily west KY up to the Ohio. We trended that direction. Thus the higher amounts that will be in our grids, for snow. The NAM remains a bit lower. Not sure in the end how much accumulation we will achieve given the antecedent ground conditions and ultimate pavement temps. One thing that could be a concern is some flash freezing, especially after dark as temperatures drop rapidly through the late afternoon and evening. Think we will go ahead and issue a Special Weather Statement to address this potential, along the the deep freeze conditions to follow for the overnight hours and Tuesday morning. .LONG TERM...(Wednesday through Saturday) Issued at 327 AM CST Sun Nov 10 2019 From a weather impact perspective, the main focus of the extended forecast period will be the anomalous, potentially record breaking, Arctic cold air at the beginning of the extended forecast period with moderation to slightly below normal during the latter half of the week into the weekend. With the strong pressure gradient with the primary and secondary cold air advection surges, wind chills will also be the most critical within the first 12-24 hours of the extended forecast (Tue/Wed) period. Will highlight wind chills in the single digits as input into the Hazardous Weather Outlook, although they are not headline worthy at this time. The general upper flow will over the region will be northwesterly through the middle part of the week, with west to northwest flow as a low amplitude ridge pattern sets up across the area, diverting systems away from the WFO PAH forecast area for the remainder of the extended. The next weather maker for the WFO PAH forecast will not occur within the next seven days, but more like into the middle of the following week. The key weather feature to monitor will be the stalled out closed low near southern California/Bajas/northwest Mexico. The eventual ejection of this weather feature and its phasing with the general upper air pattern, will determine whether there will be significant weather closer to the 20th of November. && .AVIATION... Issued at 1121 PM CST Sat Nov 9 2019 With the 06z Sunday WFO PAH TAF issuance, the first VFR ceilings below 10kft AGL are introduced into the KMVN, KEVV, and KOWB TAF locations in advance of the leading edge of the Arctic cold front after 00z Monday. Otherwise, VFR conditions with generally unrestricted ceilings and visibilities will be the rule for the remainder of the WFO PAH TAF locations. General aviation should see minimal impacts within the local area of TAF responsibility by WFO PAH. Any impacts near the end of the TAF period will be over southern Illinois and southwest Indiana along the interstate 64 corridor (from a landmark perspective). && .PAH WATCHES/WARNINGS/ADVISORIES... IL...None. MO...None. IN...None. KY...None. && $$ SHORT TERM...08 LONG TERM...Smith AVIATION...Smith