Area Forecast Discussion
Issued by NWS Jackson, KY

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640
FXUS63 KJKL 151810 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
210 PM EDT Thu Apr 15 2021

.UPDATE...
Issued at 140 PM EDT THU APR 15 2021

Did a quick update to the grids mainly to fine tune the sky cover
with the fair weather, lifting cu field over the eastern portion
of the CWA. Also added in the latest obs and trends for the T/Td
grids - running just a tad cooler than forecast. These updated
grids have been sent to the NDFD and web servers along with a
freshened NPW for the frost advisory.

UPDATE Issued at 1040 AM EDT THU APR 15 2021

14z sfc analysis shows high pressure building into the area from
the west and this is pushing much of the earlier clouds out of the
area. Some late night clearing and a moist ground allowed areas of
fog to develop, but now those have dissipated. Currently readings
are generally from the mid 40s to lower 50s while dewpoints vary
from the mid 30s north to the mid 40s in the far southeast. Winds
run from the northwest at 5 to 10 mph with some gusts to 20 mph
noted. Have updated the forecast mainly to fine tune the sky cover
and remove the fog, but also added in the latest obs and trends
for the T/Td grids. These updates have been sent to the NDFD and
web servers along with a freshening of the zones and SAFs.

UPDATE Issued at 726 AM EDT THU APR 15 2021

Ingested the latest obs into the hourly forecast grids to
establish new trends, and added areas of fog to the Big Sandy
River valley per latest obs from coop observers. Any existing fog
should dissipate and/or lift by 9 am. The forecast in general was
in good shape with no update to the zone forecast text product
required.

&&

.SHORT TERM...(Today through Friday)
Issued at 437 AM EDT THU APR 15 2021

Fog has formed in the Cumberland and Kentucky River valleys
overnight through early this morning, so the forecast grids were
updated to reflect this. After a day of much cooler temperatures,
some wind, and clearing skies, we will be in for a night of near
calm winds, clear skies, and cold temperatures. At this time,
conditions appear prime for frost formation around eastern
Kentucky late tonight, with the valley locations seeing the most
widespread frost. A frost advisory has been hoisted to account for
the frost we are expecting tonight. The advisory will be in
effect from 2 am to 9 am EDT Friday. Temperatures the next couple
of days will be below normal area wide. Aside from this mornings
fog, which should be gone by 13Z, and tonights frost, the weather
will be calm and dry albeit cooler than we are used to this time
of year. The latest CONSRAW data was used for temperatures and
dewpoints around the area today through tomorrow, while the latest
CONSALL data was preferred for cloud cover and winds.

.LONG TERM...(Friday night through Wednesday)
Issued at 510 AM EDT THU APR 15 2021

The period is expected to generally be characterized by an upper
level ridge centered over the eastern Pacific and extending into the
western Conus at times with downstream troughing extending from
Canada into portions of the central and eastern Conus. To begin the
period, an upper level low is expected to be centered near Cape Cod,
shortwave ridging extending across portions of the TN Valley and
Lower OH Valley, and an upper level trough extending from Canada
into the central Plains. An upper level low is expected to be
centered near the NE and KS border at that point. Further west a
shortwave trough is expected to be slowly working south across
portions of the Great Basin and Rockies while an upper level ridge
is expected to extend across portions of the eastern Pacific into
the Pacific northwest and western Canada. Also to start the period,
a ridge of sfc high pressure is expected to extend into the Lower OH
Valley region.

Although model guidance is in good agreement with the overall
pattern during the period, models vary some from run to run and
model to model with the timing and strength of individual
shortwaves to end the weekend and into the middle of next week.
The consensus of the guidance is that the upper level low
northeast of the area will move into the Maritimes this weekend
while the axis of the shortwave ridge crosses the area to begin
the period on Friday night. Meanwhile, the upper low will weaken
to an open wave and approach the lower OH Valley and East KY
Friday night and move across the area on Saturday. At the same
time, a sfc low is expected to move east to the south of the area
near the Gulf Coast. This combination will lead to shower chances
on Saturday with the highest chances generally in the south. Pops
were increased some compared to the previous forecast. NBM and
individual model guidance and MOS values suggest further increases
may be needed to pops as Saturday approaches. An additional
shortwave or two with more limited moisture will work across the
area on Sunday to early on Monday. These should bring clouds and
additional chances for light showers to end the weekend. A period
of height rises/upper level ridging and sfc high pressure should
lead to dry weather following for Monday and through at least
Monday night.

Models are in decent agreement in a shortwave trough dropping
south across the northern Plains/northern Rockies and into
central US from Sunday night into Monday night, which leads to
the trough sharpening up as it approaches late in the period. An
associated sfc cold front should also approach the lower OH Valley
Tuesday. This system will lead to additional shower chances,
mainly from Tuesday night into Wednesday.

Temperatures will generally remain below normal through the
period, particularly for daytime highs, generally in the upper 50s
to upper 60s. At this point, the warmest day appears to be
Tuesday with mid to upper 60s highs commonplace in advance of an
approaching cold front.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
ISSUED AT 210 PM EDT THU APR 15 2021

Just some fair weather cu out there at issuance. These will
dissipate towards evening with only some high clouds to impact the
eastern Kentucky airspace through midday Friday. Winds will be
around 10 kts with gusts to 20 kts through the rest of the
afternoon before diminishing this evening and remaining light into
Friday morning. They will pick up again by late morning generally
still from the northwest at 5 to 10 kts. Unlike this morning,
most of the low level moisture around will go to frost formation
in the valleys and elsewhere rather than fog - with no impacts on
aviation conditions.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
Frost Advisory from 2 AM to 9 AM EDT Friday for KYZ044-050>052-
058>060-068-069-079-080-083>088-104-106>120.

&&

$$

UPDATE...GREIF
SHORT TERM...AR
LONG TERM...JP
AVIATION...GREIF



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