Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 201816 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED National Weather Service Jackson KY 216 PM EDT Mon Mar 20 2017 .UPDATE...
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Issued at 216 PM EDT MON MAR 20 2017 Thunder has ended across the area early this afternoon, with showers on the demise quickly. Surface winds have turned gusty on the backside of the MCS, with a good pressure gradient set up between northeast Kentucky and southern Ohio. New convection is firing up across central Indiana, closer to a surface low and approaching short wave trough. This convection will skirt by to our northeast this evening and into the overnight as the cold front drops southeast across our area. Temperatures continue to flounder along and north of the Hal Rogers Parkway and Highway 80 corridors. Will have to retard the warm up even more so, resulting in cooler highs still. Updates will be forthcoming. UPDATE Issued at 1221 PM EDT MON MAR 20 2017 Showers and isolated thunderstorms continue to gradually weaken overall; however, the coverage has expanded further south, so increase POPs to match the radar trends better. Reduced the high temperatures in the northeast somewhat with the lingering cloud cover, but still think that a quick comeback may occur late today, as readings have already warmed into the upper 50s in our far southwest. Updates have been sent. UPDATE Issued at 1029 AM EDT MON MAR 20 2017 Weakening MCS is makings its way into eastern Kentucky, with even some minor development occurring all the way to the Tennessee border. A continued diminishment is expected into early this afternoon, as the forcing remains weak across the area. Did update POPs to represent radar trends a bit better over the next few hours. Also slowed the diurnal rise a bit more in the north through early this afternoon, with the precipitation and heavier cloud cover in place. Will reassess the highs in the next few hours. UPDATE Issued at 805 AM EDT MON MAR 20 2017 Hourly pops have been updated to account for radar and convective allowing model trends for the convective complex moving across parts of IL, IN and OH. This led to an increase in pops across the northern portion of the CWA. The few HRRR runs bring this or what is left of the complex across the area toward midday to early afternoon period. This timing might be an hour or two slow per radar trends and up to chance pops have been used accordingly to account for this. Also, temperature, dewpoint, sky and wind grids have been adjusted based on these and observation trends.
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&& .SHORT TERM...(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. && .AVIATION...
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(For the 18Z TAFS through 18Z Tuesday afternoon) ISSUED AT 216 PM EDT MON MAR 20 2017 Generally VFR conditions will hang on through this evening, as a weakening complex of showers and isolated thunderstorms exits off to our east. Additional showers and a few thunderstorms will move into the area this evening and into the overnight as a cold front drop southeast across the area. Better coverage will generally occur along a line from KSYM to KSJS, with more scattered activity expected west of I-75. Ceilings will drop down to MVFR and eventually IFR towards dawn, as south to southwest winds of 5 to 10 kts become northerly behind the cold front, and low level stratus sets in across the area. Additionally, some marginal wind shear will set up across LOZ and SME tonight, as a low level jet ramps up across the Ohio Valley.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GEOGERIAN SHORT TERM...JP LONG TERM...AR AVIATION...GEOGERIAN is the U.S. government's official web portal to all federal, state and local government web resources and services.