Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 241815
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
215 PM EDT Tue Apr 24 2018

.UPDATE...
Issued at 215 PM EDT TUE APR 24 2018

Just a few tweaks to the grids for the early afternoon update.
Band of showers is beginning to take shape over the far east as
expected. No update to the zones ATTM.

UPDATE Issued at 1208 PM EDT TUE APR 24 2018

Forecast is pretty much on track. Updated the zone package to
freshen up wording. Also increased PoPs across the far east a bit.
Last few hours HRRR has been consistently developing a band of
more moderate shower activity generally along and northeast of
U.S. Highway 460. Can not rule out a few rumbles of thunder
either, especially with some areas getting a peak at the sun from
time to time. Rain has dissipated and is moving out of areas
within the Flood Advisory. Will let the advisory run its course
to allow for excessive runoff to subside as well.

UPDATE Issued at 1000 AM EDT TUE APR 24 2018

Grid are in good shape and forecast is on track. Only had minor
tweaks to hourly temps and dew points. Will plan on a late morning
update to remove morning wording from the zone package. Otherwise,
did issue a flood advisory for portions of our southwest. Twenty-
four hour rainfall totals have been around 1.5 inches. Training of
moderate showers through the area will lay out about another half
inch by mid-day. As a result suspected there could be some minor
flooding, especially in poor drainage areas.

UPDATE Issued at 642 AM EDT TUE APR 24 2018

Forecast seems to be in pretty good shape so far this morning.
Near term POP forecast is matching quite well with the current
radar. Latest HRRR and NAM 12 are trying to show a dry slot
working its way in across a portion of the CWA through the early
afternoon, however this is not being mimicked by the Hi-res ARW
or NMM. Confidence wasn`t great enough to warrant a changing of
the forecast, but this will be something to keep an eye out for as
we head through the day. Also made sure the near term forecast
was on track with the latest observations for temps, dew points,
and winds. All updates have been published and sent to NDFD/web.

&&

.SHORT TERM...(Today through Wednesday)
Issued at 414 AM EDT TUE APR 24 2018

A strong 500mb low is currently making its way across western
Kentucky and Tennessee, while the associated surface low is just
slightly farther SE, moving into the Carolinas. The surface low is
quite expansive, encompassing much of eastern TN as well at 12Z.
This surface low will continue to strengthen throughout the day and
into tonight as it moves NE across the Carolinas, reaching Virginia
by 12Z Wednesday. The upper level low will shift just east of
Kentucky by this point as well. After 12Z, the system will continue
to ride up the eastern Atlantic seaboard, with the upper level low
losing considerable strength as it becomes absorbed into a larger
system over the lower Great Lakes. Meanwhile, broad high pressure
will move southeastward, taking hold across Kentucky for the day
Wednesday.

As for sensible weather, despite light easterly winds at the
surface, winds in the mid and upper levels will be due south,
pulling ample moisture into the region and resulting in widespread
rainfall through much of the day. There still looks to be a brief
period in the late afternoon where soundings show enough instability
during peak heating to produce a few rumbles of thunder. Ingredients
are not overwhelming, however, especially as you head northward
through the CWA, so did not go any higher than an isolated mention.
QPF should generally be a half inch or lower through the day, but
any heavier showers/thunderstorms could easily surpass this.

Heading into the overnight, we start to see the system shift
eastward and winds quickly transition to a more northward direction
in the mid and upper levels, and NW in the lower levels. This will
cut off some of the influx of moisture, however we will still be
able to tap into wrap around moisture from the system, so expect
continued scattered but light rain shower potential throughout the
night. Did keep mention of numerous showers in the far SE portion of
the state where upslope flow will play a large factor. By Wednesday,
the system will continue to drift away from the region as drier high
pressure takes hold from the west. Pops are expected to slowly
diminish from west to east throughout the day, once again holding on
the longest in the far SE with continued favored NW flow.

Given the abundance of clouds and rain across the region,
temperatures will be fairly uniform and mild. Highs both today and
tomorrow will be in the low 60s, with overnight lows in the low 50s.

.LONG TERM...(Wednesday night through Monday)
Issued at 437 AM EDT TUE APR 24 2018

Whatever active weather there is during the period looks like it
will be in the first few days. Light rain on the trailing edge of a
storm system moving up the east coast could still be affecting our
far eastern counties Wednesday evening, but will be on the way out.
At least a brief break in precip is then expected into the day
Thursday.

By late Thursday, rain could again be in the picture from another
upper low moving slowly across the southeast CONUS (the system
currently over MT, WY, and the Dakotas). It`s uncertain how far
north the rain will occur. The GFS and NAM both have light precip in
our southern counties late Thursday into Thursday night, while the
ECMWF keeps it to our south. Considering a similar model scenario
played out in advance of the system currently bringing us rain, the
American models will be given consideration and a chance POP will be
carried near the TN border. Whatever plays out, the system is
expected to depart Thursday night.

After only a brief break, a cold front is expected to arrive Friday
evening (supported by an upper level trough currently offshore of
British Columbia). Moisture looks to be very meager, and the ECMWF
is dry and the GFS only has very light precip in our far north. The
situation does not seem to justify anything more than a slight
chance of showers at the northern edge of the forecast area. After
this, ridging at the surface and aloft is forecast to build into the
area, resulting in dry weather Saturday through Monday, with highs
nearing 80 by Monday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
ISSUED AT 215 PM EDT TUE APR 24 2018

Storm system over the TN and OH valley continues to rotate to the
east, at present centered roughly over south central Kentucky. As
expected there is a band of showers beginning to take shape
across the east. HRRR seems to have had a good handle on this
feature. As such did include a VCTS for SJS for a few hours early
in the period, especially with a bit more sunshine in the east.
However, convection is expected to be isolated and widespread
enough to exclude any mention of thunder at other terminals.
Flight conditions will generally deteriorate through the evening
and overnight, mainly for CIGS as they drop into IFR/LIFR
territory. Winds will generally be light and variably but will
gradually turn out of the northwest as the storm center continues
to push eastward.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

UPDATE...RAY
SHORT TERM...JMW
LONG TERM...HAL
AVIATION...RAY



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