Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 162008 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 408 PM EDT Sat Mar 16 2024 .KEY MESSAGES... - Temperatures will remain about 5 to 10 degrees above normal through tonight. - A deep trough passing aloft brings a threat of some rain/snow showers on Monday. - Hard freeze conditions Monday night could kill any cold sensitive vegetation that has emerged prematurely due to early season warmth. - Temperatures rebound back to near normal through mid-week, with lower confidence in the next potential chance of precipitation moving in towards the end of the work week. && .SHORT TERM...
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(This evening through Sunday night) Issued at 408 PM EDT SAT MAR 16 2024 Late this afternoon, an upper level low was centered over western Ontario with the axis of a shortwave trough extending into the western Great Lakes region to the mid MS Valley vicinity. Additional weaker shortwaves were upstream moving south into the 500 mb trough. In advance of the approaching 500 mb trough axis, 500 mb heights have begun to slowly fall across eastern KY. At the surface, a ridge of high pressure extended from the TX and OK panhandle areas to the TN Valley to eastern KY and WV. Meanwhile, a sfc low associated with the upper low in Ontario was also centered in Ontario with a cold front trailing into the Great Lakes region to Central Plains. Ahead of the boundary, temperatures have warmed to the low to mid 60s in most locations, or about 5 degrees above normal for mid March. Some mid and high clouds were also moving across the OH Valley region in advance of the sfc cold front and the upper level trough. This evening and tonight, the axis of the sfc ridge of high pressure will slip to the southeast of eastern KY. Meanwhile, the sfc low will track from Ontario and into Quebec with the trailing cold front dropping into and across the OH Valley including the Commonwealth. Meanwhile at 500 mb, the trough axis will effectively remain west of eastern KY while an initial shortwave works across the Great Lakes and the Lower OH Valley as the trough is reinforced by shortwave dropping into it from the north tonight and into Sunday. Cold air advection is expected behind the front for Sunday and Sunday night. 850 mb temperatures are forecast to drop to about the 0C to 4C range by dawn on Sunday and then fall a few more degrees C trough Sunday evening with a bit more dramatic drop on Sunday night to about -5C to -9C to end the period. Ahead of the front tonight, deeper valleys will likely decouple once again and drop toward the 40 degree mark, if not the upper 20s in some instances. These temperatures may rebound later in the night near the time of the frontal passages. Otherwise, the front is expected to be too moisture starved for any precipitation those low to mid clouds will increase as moisture is progged to increase generally near the 850 mb level and above to about the 750 mb level. Winds should become a bit gusty behind the front Sunday as the colder airmass is ushered in with some gusts upwards of 20 mph. Despited the cold air advection on Sunday, temperatures should climb to near normal. Sfc temperatures drop to under the cold air advection on Sunday night to about 5 degrees below normal and the colder airmass ushered in will set the stage for even colder lows early in the long term period. .LONG TERM...(Monday through Saturday) Issued at 400 PM EDT SAT MAR 16 2024 The 16/12z model suite is in reasonably good synoptic agreement Monday morning but still shows substantial deterioration, especially after Wednesday. On Monday morning, a mean trough is in place over Quebec/Eastern Ontario with an associated surface low over the Gulf of St. Lawrence. A vigorous shortwave trough, extending from the Eastern Lake Great Lakes to Mid-Mississippi Valley, is riding around the southwestern periphery of the trough. Surface high pressure spans west and north of the shortwave from northern Ontario to the Southern Plains. Further west, an ~575 dam high is found over the Pacific Northwest while an ~561 dam low is found over Arizona. Another weak disturbance is passing over northeast Saskatchewan between the ridging over the Pacific Northwest and troughing over eastern Canada. The leading vigorous upper level shortwave trough will pass over the Ohio Valley/Central Appalachians on Monday into Monday night. This will spread a chilly airmass across eastern Kentucky with 850 mb temperatures bottoming out to near -10C by late Monday -- cold enough for any precipitation to fall as a mix of snow and rain or all snow. Uncertainty lingers as to how much moisture will be available to this system. Model guidance continues to offer solutions ranging from a completely dry scenario or spotty light QPF of up to a few hundredths, primarily in the north and east. The potential for moisture-enhancement from Lake Michigan appears to have diminished as modeled low-level flow has largely trended too westerly. Due to the resulting decline in model suite QPF, PoPs were limited to the 10 to 20 PoP range for locations northeast of US-421. Of note, the last few hours of the 15z RAP13 show soundings becoming much more favorable for at least some snow shower activity. Hopefully, confidence in the occurrence of any snow showers or flurries will improve as the entirety of day comes into the range of the CAM suite. Whatever moisture materializes for Monday should depart quickly Monday evening as high pressure shifts from the Plains toward the Southeast US. In any case, northwesterly winds will be blustery, gusting to between 20 and 25 mph on Monday before subsiding Monday night. Additionally, the air mass will be quite chilly with Monday`s high temperatures only in the upper 30s to mid 40s and frosty cold Monday night lows deep into the 20s. A few upper teens cannot be ruled out the most sheltered valley locales. Looking ahead to Tuesday, the low level flow will quickly turn more westerly ahead of second upper level shortwave trough riding around the parent upper level trough. This system;s track is slightly further to the east than the previous shortwave, but will still drop another cold front into eastern Kentucky from the north on Wednesday. No measurable precipitation is forecast with the boundary. Ahead of the front, temperatures will make a quick rebound on Tuesday back to between 50 and 55 for most locations. Wednesday highs should be even warmer, reaching the mid 50s north of I-64 where the front arrives early in the day and up to the mid 60s in the far southeastern valleys where the front moves in later in the day. The core of the chillier air with the second cold front will move into the Eastern Great Lakes/Mid-Atlantic Wednesday night and Thursday, brushing our area in the process. Compared to 24 hours ago, somewhat colder air may seep into eastern Kentucky by Wednesday night and Thursday. This has led to a lowering of the minimum temperatures on Wednesday night to between 27 and 36. On Thursday, the NBM maximum temperatures were also adjusted lower toward a blend of the the raw model data, yielding highs around 50 in the northeasternmost locations of Elliot, Rowan, and Fleming counties up to around 60 in the deepest valleys near the Tennessee border. Later in the week, the forecast still becomes notably less certain due to considerable run-to-run and model-to model-spread. Guidance is struggling with how the closed low initially over the Desert Southwest interacts with northern stream energy passing over the northern CONUS. It does seem, that a period of increased PoPS is probable in most scenarios. Accordingly, the NBM forecast was retained for Friday through Saturday and shows PoPs peaking at high chance (40 to 50%) on Friday while temperatures rise back to near normal levels.
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&& .AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon) ISSUED AT 1236 PM EDT SAT MAR 16 2024 As of midday, fog and stratocumulus was mixing out with any lingering instances of MVFR or IFR quickly trending to VFR. Overall, VFR prevailed in most places as of 1630Z. Winds will become southwest to west early in the period in the 5 to 10KT range through about 06Z. Then, as a cold front drops across the are, winds will shift to the west and then northwest late in the period again at 5 to 10KT. Despite the passage of a cold front, it will be rather moisture starved and VFR will prevail through the end of the period. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...JP LONG TERM...GEERTSON AVIATION...JP

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