Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 170800
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
400 AM EDT Tue Apr 17 2018

.SHORT TERM...(Today through Wednesday)
Issued at 400 AM EDT TUE APR 17 2018

Radar still suggests a few flurries may be lingering north and west
of Highway 80, but these will diminish by daybreak as drier air and
subsidence settle into eastern Kentucky. This will bring mainly
clear skies for all this morning and early afternoon as stratus
erodes from southwest to northeast. Westerly winds will once again
pick up by mid-late morning and continue at around 10-20 mph with
gusts up to 25-30 mph through this afternoon, owing to roughly 25
knots of boundary layer wind below a strengthening subsidence
inversion. Building mid-level heights on the eastern flank of
shortwave ridging will promote warm air advection, with temperatures
rebounding into the mid-upper 50s for much of eastern Kentucky.
Spots south of Hal Rogers Parkway look to top out in the low 60s
nearer the influx of warmer air.

A disturbance moving across the central Rockies and Great Plains
will result in a surface low ejecting out of the Front Range into
the Central Plains this evening. This surface low will translate to
along the Interstate 44 corridor tonight and continue east across
the lower Ohio Valley Wednesday, bringing a warm front into eastern
Kentucky. Increasing low level moisture, in conjunction with the
southwestern edge of cyclonic flow stemming from our previous upper
low now across the St. Lawrence River Valley, may be enough for a
few sprinkles across portions of northeast Kentucky late this
evening into tonight. Have opted to keep this out of the forecast
for now as adequate enough moisture recovery all the way to the
surface will be hard to come by so soon. Nonetheless, expect an
uptick in cloud cover through the night. This should limit the
potential for frost across the northern Bluegrass region, as well as
put somewhat of a damper on previously expected ridge/valley
temperature splits. Did keep a noticeable split in at this time, but
kept the largest difference confined to the Cumberland Valley where
low clouds may not be quite as extensive/thick.

A much more appreciable warmup will be in the offing for Wednesday
as warm air advection continues on increasing southwesterly flow.
May need a Lake Wind Advisory late Wednesday morning through the
afternoon as the pressure gradient increases in response to a 1003
mb surface low maintaining its intensity along the Ohio River. Wind
speeds should near 20 mph with gusts likely exceeding 30 mph as
temperatures warm into the low-mid 70s. Shower chances will increase
through the afternoon as the previously mentioned upper low
approaches the southwestern Great Lakes and ushers a cold front
toward eastern Kentucky. Any precipitation amounts, if any,
Wednesday afternoon look extremely light.

.LONG TERM...(Wednesday night through Monday)
Issued at 400 AM EDT TUE APR 17 2018

There is relatively good model agreement early on in the period. A
cold front will be approaching from the northwest as the period
starts, and should pass through on Wednesday night. Moisture will be
limited, and forecast soundings show precip which occurs would be
rain showers due to shallow convection, with amounts being light.
The GFS has some showers potentially lingering into Thursday, while
the ECMWF and NAM are dry. The resulting blend/compromise yields a
mostly dry forecast for the day Thursday.

A large area of surface high pressure will pass to our north to end
the week. It will initially supply another chilly air mass, with
frost possible Thursday night and Friday night, but readings will
moderate for the weekend.

The ECMWF and GFS then start to show more significant differences
which impact our area. The culprit has its origins with a system
currently well offshore of the Pacific Northwest coast. The
associated upper level low is expected to drop southeast over the
southwest CONUS, and then trudge eastward. The GFS has a more
northerly track with rain making it into the JKL forecast area, and
the ECMWF has a more southerly track with rain staying to our south.
At this time, the POP has been held to 10-30% Sunday through Monday.
Greater forecast certainty will need to wait until the system is
better sampled and closer in time, when models hopefully will show
better agreement.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
ISSUED AT 154 AM EDT TUE APR 17 2018

Lingering MVFR ceilings across far eastern Kentucky will lift to
VFR levels by daybreak as west winds continue to subside
overnight with speeds generally below 10 knots. As skies continue
to clear from southwest to northeast this morning, west winds will
increase to 10-15 knots with gusts approaching 20-30 knots at
times from mid morning through this afternoon. A weaker pressure
gradient will result in very light to near calm winds tonight as
an approaching warm front results in some renewed low level
moisture. This increase in moisture may be enough to lead to some
developing ceilings, but these currently look to remain in the VFR
category.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
Freeze Warning until 10 AM EDT this morning for KYZ044-050>052-
058>060-068-069-079-080-083>088-104-106>120.

&&

$$

SHORT TERM...GUSEMAN
LONG TERM...HAL
AVIATION...GUSEMAN



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