Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 301635 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 1235 PM EDT Thu Mar 30 2017 .UPDATE...
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Issued at 1235 PM EDT THU MAR 30 2017 Temps have outpaced what was forecast, and a couple degrees has been added to the max temps for today. Otherwise, few changes have been made. UPDATE Issued at 1017 AM EDT THU MAR 30 2017 No significant changes were made at this point. Early morning showers have moved out of the area. Did make a minor change to raise the POP above zero area wide for the rest of today, with a peak 10% category in the eastern part of the area. Can`t rule out some showers popping up, but the potential is still too low to make a mention of it in the worded forecasts. UPDATE Issued at 657 AM EDT THU MAR 30 2017 The narrow band of showers that had formed over central Kentucky earlier is now crossing our northern counties and actually producing some pretty decent thunderstorms at the moment. Did a quick update to toss thunder in with this morning activity. All of it will be exiting east in the next few hours, leaving behind dry conditions for the remainder of the daylight hours today. Latest HRRR/RAP show convection this evening starting to roll into eastern Kentucky between 8 and 11 PM. This is in line with the current forecast. Thus, no other changes needed right now. Grids have been saved an sent to reflect the thunder over the next hour or two.
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&& .SHORT TERM...(Today through Friday) Issued at 309 AM EDT THU MAR 30 2017 An area of low pressure resides over eastern Kansas this morning with a warm front extending east across central Missouri and into western Kentucky. A cold front is advancing eastward across the Ozarks region. Isentropic ascent associated with the warm front advancing towards eastern Kentucky has led to a increase in mid/high clouds this morning. Still some support in the hi-res short term models to support some light showers/sprinkles early this morning as the isentropic ascent in the mid levels continues to increase. In fact, a few showers are already trying to get going out across central Kentucky and this should continue to expand in coverage as it moves northeastward. The threat for showers will be short lived as downsloping south-southeast flow takes hold through the day. This leads us to our first threat of the day, an enhanced fire danger. Temperatures will soar to around 80 this afternoon. Dewpoints should mix out into the mid to upper 40s, putting relative humidities between 25 and 35 percent areawide. While this is not in the critical range, it is close. In addition, winds will crank up this afternoon with deep mixing taking place. Sustained winds of 10 to 20 mph are likely along with wind gusts up to 35 mph. The dry air combined with these strong winds could will create an enhanced fire danger today, especially for areas that have managed to dry out over the past 24 to 36 hours. Will highlight the fire danger in the HWO and fire weather forecast this morning. As we head into the evening hours, the low over Kansas this morning will push east across central Illinois and Indiana. The trailing cold front will lead to shower and thunderstorm developing across southern Illinois/Indiana, southward into western Kentucky and western Tennessee. This activity will push east/northeast through the evening hours. This activity will be aided by a potent shortwave it it tracks into eastern Kentucky tonight. This leads to our second threat, severe storm potential tonight. Shear will be tremendous with this system, but instability may be a bit more of a question. With dewpoints slow to come up through the day, the question is, can we generate enough instability to allow for a more robust severe threat. Certainty a questionable setup for eastern Kentucky given the lack of surface instability. However, in this case, we have lots of forcing spreading east across the area and this could compensate for the lack of instability. The storm prediction center has expanded the slight risk of severe storms over all of eastern Kentucky and this seems very reasonable considering the trends. The enhanced risk is sitting just to our west, and would not be surprised to see it expanded west today depending on how things unfold upstream. Best threat would be in our western counties as these areas are less likely be be downsloped and thus dewpoints more likely to come up in these areas. Things become more questionable to the east. Main threats appear to be damaging winds and large hail, although a brief tornado spin up cannot be ruled out. Heavy rainfall will be possible with strong lift associated with the shortwave and PW`s near 1.25 inches. This could produce some rainfall totals in excess of 1 inch tonight. Forcing will depart to the east early Friday morning, but the upper level trough will become anchored over the region keeping some moisture and cloud cover over the region. This may lead to scattered to numerous rain showers Friday afternoon. Mid level lapse rates not quite steep enough to support thunder, but are very close. Should be a much cooler day with highs in the 60s. .LONG TERM...(Friday night through Wednesday) Issued at 450 AM EDT THU MAR 30 2017 The models are only in broad agreement on the pattern aloft and just through the first part of the extended portion of the forecast before diverging by start of next week. The split nature of the flow through North America continues to give the models trouble with respected to timing and placement of the key features through next week. The first of these is a trough departing to the northeast late Friday into Saturday morning. While the models are different, even at this early stage, these discrepancies will have little effect on eastern Kentucky`s weather in an environment of rising heights and a building ridge throughout the region. Ridging peaks over Kentucky early Sunday before a broad and rather open trough moves east through the Southern Plains. The GFS is a tad stronger, faster, and off to the northeast of the ECMWF version with this trough while the CMC is more similar to the latter model. Southwest flow over the region will carry energy into our area through the end of the weekend. The core of the trough itself will slowly move to the lower Mississippi Valley while a significant wave lifts northeast through Kentucky out ahead of the main trough. At this point, the GFS remains more open with its trough than the ECMWF and also exhibits more of a connection with the faster northern stream. The net result is that the GFS takes the core of its mid level low through the Tennessee Valley ahead of the ECMWF by as much as 12 hours with the CMC in between. These significant differences carry through the day Monday and into early Tuesday before all models take the lower heights off to the east and allow for a return of mid level ridging over Kentucky. These differences lower the confidence in any specific solution from the models, but do indicate that we will see a wx maker moving through during this time frame - and likely a tad quicker or slower than suggested by the consensus solution depending on how reality breaks with the progs. For now, will favor a blend with a preferred lean toward the CMC and ECMWF - slowing the arrival and departure of the sensible wx effects. Ridging will dominate the rest of the extended but another strong trough does approach from the west late Wednesday - again faster in the GFS than the ECMWF. Sensible weather will feature a cool and cloudy start to the weekend before high pressure moderates and warms for Sunday. Showers and thunderstorms will then be possible by Monday morning as a deep southern surface low plods east toward the area. This looks to pass right over Kentucky keeping high PoPs in the forecast along with a chance for thunderstorms. The damp weather will dry out later Tuesday with little cool air to be found in its wake continuing the mild temperatures through the rest of the extended, particularly on Wednesday where low to mid 70s are anticipated for the afternoon. Did make some minor adjustments to the lows early and late in the period to account for the terrain distinctions outside of the rainier ones to start the new week. As for PoPs - have tempered them a bit from early Monday through Tuesday owing to the model differences and lower confidence in their individual solutions - though showers will be in the likely range for much of this time frame. && .AVIATION...(For the 12Z TAFS through 12Z Friday morning) ISSUED AT 657 AM EDT THU MAR 30 2017 VFR conditions will prevail through this evening. Some mid/high level clouds will be drifting across the area through this evening. Showers and storm chances will increase after 00z this evening. With the onset of convection, we may see a period of MVFR cigs and visbys with the storms with cigs lowering to low end MVFR by daybreak Friday. We may even be able to squeeze out some patchy IFR cigs late tonight. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...HAL SHORT TERM...KAS LONG TERM...GREIF AVIATION...KAS

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