Area Forecast Discussion
Issued by NWS Jackson, KY
FXUS63 KJKL 201815
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
215 PM EDT Thu Oct 20 2016
Issued at 215 PM EDT THU OCT 20 2016
Finally seeing an increase in shower activity over the past hour
as low pressure continues to move up the Ohio River Valley. A
trailing cold front aligned along the Ohio River is beginning to
move southeast towards our area. This cold front should pass
through our area late this afternoon through this evening.
Updated grids to bring them in line with latest hourly trends.
Refreshed wording in the zones as well.
UPDATE Issued at 953 AM EDT THU OCT 20 2016
Quick update this morning to bring grids in line with hourly obs.
Forecast is on track. Shower activity will be on the increase
through the day as a couple of surface waves track along the Ohio
River and a cold front approaches from the west. Most of any
activity will be isolated to at best scattered through the
morning with the bulk of activity holding off until later today.
No update to the zone package at this time.
UPDATE Issued at 627 AM EDT THU OCT 20 2016
WSR-88D radar is showing some isolated showers moving in from the
Cumberland Plateau region. Overall coverage will remain isolated
until we move into the afternoon when showers and some
thunderstorms develop and move across the region. Overall the
grids are on track, but did expand the slight pops to cover
ongoing showers. Also updated with latest obs and trends.
.SHORT TERM...(Today through Friday)
Issued at 355 AM EDT THU OCT 20 2016
Morning surface analysis shows the quasi-stationary boundary
remains NW across the Ohio River. A secondary cold front further
NW of the previously mentioned boundary. The boundary across the
Ohio River region will eventually progress east across eastern KY
this afternoon and evening. In terms of AM POPs did keep slights
ahead of the boundary, as the LLJ kicks in and perhaps a bit of
mid level forcing. These showers are actually showing up across
Middle TN and portions of the Cumberland Plateau on radar this AM.
However the bulk of our rainfall will come from the actual
cold front and upper level wave. Right now we are looking at
around three quarters to one inch of rainfall across the region
through Friday. That said we also remain in a marginal risk for
severe storms today from the SPC. We do have reasonable effective
bulk shear values approaching 40 knots and reasonable instability.
The question is how much instability with 4KM NAM remaining the
more robust in relation to this, and not sure if we will realize
the NAM numbers at this point given potential cloud cover. Overall
CAMs would suggest a broken line will progress across the region
between 21z and 00z. Given that would think the chances for
marginally severe wind gusts are possible with some of these line
segments. Now in terms of temps did come up from model blend
particularly in the south and east for this afternoon where less
cloud cover is possible early.
Tonight the cold front will move out of the region, and POPs will
slowly decrease from west to east toward dawn. The big news will
be the colder airmass, as the base of the upper level trough axis
swings across KY. This and secondary cold front will lead to a 15
to 20 degree drop in temps for Friday, as temperatures struggle
to rise out of the 50s. This all as NW flow aloft leads to cloud
cover and 850mb CAA continues to work in with temps in the 0 to 2
C range from NW to SE by the afternoon.
.LONG TERM...(Friday night through Wednesday)
Issued at 412 AM EDT THU OCT 20 2016
The models remain in general agreement with an amplified long wave
pattern to control across the CONUS this weekend into early next
week. Deep troughing will become established across the eastern
Pacific, with ridging across the Plains and into the Midwest.
Meanwhile, another trough will pull towards the eastern Seaboard,
and eventually wrap up into an upper level low across eastern
Canada. Towards the end of the period, the flow looks to flatten
out somewhat, as the troughs relax in the west and east.
Eastern Kentucky will start out under the influence of a trough,
with a few showers likely lingering into Friday evening, before
ending from west to east. A much cooler air mass will funnel in on
northwest winds by Saturday morning. Some 30s are expected in the
higher elevations in the southeast, as well as locations west of
I-75, which will stand the better chance of partial clearing.
Saturday will be the coolest daytime highs we have seen since May,
as readings will only climb into the mid to upper 50s. This will
set the stage for more widespread 30s for the valleys by Sunday
morning, as skies clear out and high pressure skirts by to our
south. Heights will rebound quickly for the second half of the
weekend, with gusty southwest winds helping to rebound highs 10
degrees or more on Sunday.
Early next week, a cold front looks to move through by early
Monday, with little consequence besides a slight increase in
clouds and a wind shift. Dry weather will hold on into the middle
of next week, before another cold front takes aim at the area
towards Thursday. Temperatures will be seasonable, with lows in
the 40s, and highs in the upper 60s to lower 70s.
.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
ISSUED AT 215 PM EDT THU OCT 20 2016
Seeing an increase in shower activity over the past hour as low
pressure moves up the Ohio River Valley. A trailing cold front
aligned along the Ohio River is beginning to move southeast
towards our area. The cold front should pass our TAF sites from
northwest to southeast late this afternoon through this evening.
Thunderstorms will be possible at any of our terminals until
FROPA. In general expect CIGs to drop into IFR/LIFR territory post
frontal. VSBYs will generally drop into MVFR categories with
showers, possibly into IFR with post frontal showers and pre-
frontal thunderstorms. Winds will veer from the southwest at 5 to
10 kts to the northwest behind the front at around 10 kts. Gusty
winds to around 25 kts will be possible in the vicinity of any
thunderstorms and briefly with and just behind the cold front.