Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 150810

National Weather Service Jackson KY
410 AM EDT Tue Aug 15 2017

.SHORT TERM...(Today through Wednesday)
Issued at 410 AM EDT TUE AUG 15 2017

07z sfc analysis shows general low pressure through the area with
high dewpoint air in place. This is prompting light to moderate
showers to traipse across eastern Kentucky this night as well as
encouraging the development of fog despite the cloudy conditions.
Winds are light with temperatures fairly uniform in the lower 70s
most places along with dewpoints in the upper 60s to lower 70s.

The models are in good agreement with the long wave pattern over
the area through the short term portion of the forecast. They all
depict slight troughing in place along with broad southwest flow
through today with embedded shortwave impulses running nearly
zonal from west to east across Kentucky. Heights will be on a
slowly increasing trends ahead of the next main trough developing
over the Pacific Northwest and inland to the Northern Plains.
Given the model similarities and the small scale nature of the key
features for sensible weather will favor a general model blend
with a strong lean toward the HRRR and NAM12 for specifics.

No well defined boundary nearby and high pw air in place will keep
confidence rather low in timing and exact locations of the best
pcpn/heavy rain threats. Have hit the southeast section of the
area a little harder than the rest of the CWA per the guidance
agreement on this tendency - along with the best chance for heavy
rains there. The clouds and convection today will limit the warm
up, but low 80s are still expected. Drier air will settle into
this part of the state later today and overnight decreasing our
shower and thunderstorm chances, but not down to below 20% for
much of the area. High dewpoints tonight will mean a repeat with
mild temperatures, not much ridge to valley distinctions, and
more patchy/areas of non-terrain discriminating fog. The next
batch of rain should be moving into the area on Wednesday, as
similar conditions will be in place with some enhancement expected
from energy packets aloft.

Used the CONSShort as the starting point for the grids through the
short term portion of the forecast with only minor, point-based
adjustments to temperatures. As for PoPs, did enhance them
diurnally and kept them more focused in the southeast parts of
the area through Wednesday.

.LONG TERM...(Wednesday night through Monday)
Issued at 314 AM EDT TUE AUG 15 2017

The extended portion of the forecast begins on Wednesday night with
an active pattern on tap across the CONUS. The period will begin
with a strong trough tracking over the northern Plains and into
the Great Lakes as it drags a cold front over the OH Valley region
during the day on Thursday. Model profiles for Thursday afternoon
show quite a bit of instability and good directional shear. This
will definitely be a set up to monitor as SPC has issued a Day 3
Marginal severe risk. At this point, models so suggest that the
bulk of the dynamics and instability will be north of the Ohio
River where the greater risk will likely be.

Thursday night and into the weekend, the mid level ridge will set
up again over the Southeastern CONUS bringing return flow into the
area. This will be combined with several shortwaves passing
through the OH Valley with the next front passing through late
Saturday. At this time, this feature does not seem to have the
amount of instability and shear as the previous front. With the
return flow continuing into next week, the threat of afternoon
showers and thunderstorms will persist through the end of the
extended forecast period. Overall, a wet extended forecast is
expected through next week.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)

Scattered showers and a stray thunderstorm or two continue to
affect eastern Kentucky early this morning. Coverage will be
highest in the south, but even SYM could see a shower, with some
increase in areal extent expected toward dawn in the far SE
portion of the state. Limited instability should keep the thunder
chances low, so just went with VCSH for all TAF sites. For
Tuesday, though, there will be more instability around likely
resulting in additional thunderstorm development in the
afternoon, but given uncertainty whether any particular TAF site
will be impacted, kept with VCTS, at this time. Winds will remain
light and variable throughout the period. Aside from the storm
threats for Tuesday afternoon, the main concern for this TAF is
the potential for low flight categories due to fog and low stratus
clouds through mid morning. With abundant moisture across the
region, we have the potential for LIFR conditions. However, can`t
rule out some brief drops below this category. Conditions should
begin improving shortly after daybreak, but expected no better
than BKN cloud cover in the low end VFR range through the
afternoon with any convection lowering the cigs/vis into the MVFR
or lower range.




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