Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 200848 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 448 AM EDT Mon Mar 20 2017 .SHORT TERM...
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(Today through Tuesday) Issued at 430 AM EDT MON MAR 20 2017 Early this morning, an upper level ridge was centered over northern Mexico and the Southern Plains with an axis of this ridge extending northeast into the eastern Great Lakes with another axis extending toward the Four Corners and Intermountain West. Several rather weak shortwave were embedded in the westerly flow from the Rockies to the Great Lakes and MS Valley between the ridge and an upper level low over Central Canada. At the surface, a deep area of low pressure was moving across Hudson Bay with a cold front that is becoming more ill defined with time extending south from this system to an area of low pressure that is nearing the mid MS Valley. A warm front extended south southeast form the low to the Gulf Coast states. Meanwhile in advance of the axis of the mid and upper level ridge and sfc high pressure generally dominating, a rather steep nocturnal inversion is in place with deeper valleys generally in the mid to upper 20s at this time while ridges other than the highest ridges were in the mid to upper 30s. Preliminary non operational/test GOES 16 WV imagery at the low, mid, and upper level channel indicate an increase in WV is dropping south and east of the OH River at this time. Regional observations indicate a mixture of mid generally mid and high clouds with this. Meanwhile rather deep convection has developed over northern IL, northwest IN, and portions of MI in advance of the front. The model consensus is for a shortwave trough moving around the central Canada upper level low to move toward the Maritimes today which should help push the weakening cold front into the eastern Great Lakes to Lower Oh Valley region by this evening while the warm front should lift across the TN and into the lower OH Valley through this evening while the surface low nears the lower OH Valley by sunset. Moisture will increase as the upper ridge axis moves east today, initially in the mid to upper levels. Convective allowing models take the weakening convection now to the northwest of the area toward northern KY and southern after sunrise and weaken it further as it moves into northeastern KY and the Huntington WV metro area around midday. With dry low levels in place, this will probably not be much more than light showers or sprinkles when or if it reaches the northern sections of the forecast area. Slight chance pops were used for much of the area north of the Mtn Parkway for this with some chance pops generally I 64 and north with a buffer of sprinkle chances just south and east of these areas. The southwestern part of the area appears to be poised to experience the least cloud cover today with a general increase in clouds area wide by the mid to late afternoon hours. Clouds and potentially some precipitation in the far north should set the stage for about a 10 degree north to south temperature gradient in highs for today from Fleming County to Wayne County. Somewhat better chances for precipitation are expected by late evening into tonight as the weak surface wave moves across the area and the frontal/baroclinic zone sags into the Commonwealth accompanied by some modest height falls. Some limited elevated instability continues to be indicated in the models mainly late this evening and tonight, so we have maintained some isolated thunder in the weather grids. The northern and east locations appear to have some better forcing this evening and tonight so chances for measurable rain appear better. Uncertainty exists though as the 0Z NAM had less convection across the area compared to some of the other guidance, but the 06Z runs appears to be in a bit better agreement with the guidance. Along and in advance of the front, temperatures will be mild tonight and min T should have at least a 10 degree range from north to south with locations in advance of the boundary remaining in the low to mid 50s tonight. Winds will increase ahead of the boundary, particularly aloft and some of this stronger sustained winds and gusts should be realized at elevations of 2500 feet and above where gusts of 30 mph or higher are anticipated from around midnight through 5 AM tonight. The next round of higher rain chances areawide may hold off until early in the long term period on Tue night. Convection some possibly strong is currently expected to develop near or just south of the sagging boundary possibly near the confluence of the OH and MS River. This convection should move east southeast and track near or a bit south of the boundary that may reside just south of the KY/TN border for much of Tuesday while more scattered weaker convection is possible across most of East KY. Chances for convection appear best across the Lake Cumberland/KY and TN border region on Tuesday afternoon. If thunderstorms do affect that area, the strongest storms could produce some small hail with relatively low WBZ heights in place. Another wave and secondary boundary will approach late, but convection from this should hold off until after the period. The north to south temperature gradient should persist for Tuesday Max T. Overall, it increasingly appears that some locations may get missed by the convection over the next couple of days completely or only experience very light qpf. .LONG TERM...(Tuesday night through Sunday) Issued at 332 AM EDT MON MAR 20 2017 There will be three periods of note in the extended. First will be the Tuesday night and Wednesday time frame. A large trough of low pressure aloft is progged to move across the northern CONUS and into New England through mid week. The surface cold front associated with the trough will be our primary weather maker to begin the period. Widespread rain showers are expected across the area to start things off. We may even see a few thunderstorms along and south of the Hal Rogers Parkway through 2 or 3Z Wednesday, as the cold front sags southward across the area. Once the front moves into Tennessee, general rain showers should be all that remain behind the front. The rain will quickly taper off during the night, with only scattered showers in place by 9 or 10Z Wednesday. Cold air intruding from the north may be enough to cause some snow to mix with the rain across the northern and northeastern portions of the forecast area early Wednesday morning. Any remaining precipitation should be out of the area by around 17Z on Wednesday. A ridge of cold high pressure is expected to settle over the region from Wednesday through Friday, and will likely bring unseasonably cool weather to eastern Kentucky Wednesday night through Thursday morning. In fact, the deeper and more sheltered valleys in the eastern portions of the forecast area may see areas of frost on Thursday morning, as temperatures fall to below freezing in those locations. Wednesday should also see below normal temperatures, due to the lingering cloud cover and precipitation. A second period of wet weather is expected this weekend, as a more vigorous area of low pressure is forecast to eject out of the Plains across the Ohio and Tennessee valley regions. The onset of rain looks to be some time Saturday morning, as a cold front approaches from the west. The best chance for rain at this time looks to be from Saturday afternoon through Sunday afternoon, as the front moves across the area, and then the parent low tracks eastward just to our north. Isolated thunderstorms will again be possible Saturday and early Saturday night, as the front moves through. The latest forecast soundings were showing enough instability aloft to support some thunder. The rain will linger through Sunday evening, as the parent low strengthens to our north and slows down. The rain should steadily taper off Sunday night into Monday morning, and should be out of the area by late Monday morning. A nice warm up should commence on Thursday, as high pressure takes hold. The warmest period should be from Friday through Sunday, as persistent southerly flow sets up across the region. Highs from Friday through the weekend are expected to average in the 60s across the area. A few locations may even reach or slightly exceed 70 degrees on Saturday. Nightly lows should also be plenty warm, with minimum values in the 40s and 50s expected.
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&& .AVIATION...(For the 06Z TAFS through 06Z Monday night) ISSUED AT 215 AM EDT MON MAR 20 2017 VFR conditions prevailed at TAF issuance. Much of the 6Z to 12Z period should be clear, although some thicker high and some mid clouds may encroach on western locations by the 12Z to 15Z period. VFR should prevail through Monday as low levels are slower to moisten up as a cold front approaches. MVFR is possible by the 0Z to 6Z period with further lowering to IFR possible along and behind the boundary in the far north at the end of the period. A bit of very light rain or sprinkles cannot be ruled out in the 13Z to 19Z period per convective allowing models mainly near SYM, SJS, and JKL along the leading edge of mid level moisture increase. Winds will average less than 10 KT, becoming southerly around 12Z and then more southwest or even west in the far north during the 0Z to 6Z period. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...JP LONG TERM...AR AVIATION...JP is the U.S. government's official web portal to all federal, state and local government web resources and services.