Area Forecast Discussion
Issued by NWS Jackson, KY

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837
FXUS63 KJKL 260535
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
135 AM EDT Tue Sep 26 2017

.UPDATE...
Issued at 800 PM EDT MON SEP 25 2017

23z sfc analysis shows a stagnant weather pattern with weak high
pressure in place over eastern Kentucky. The only clouds out there
are some high ones loosely connected to the outflow from Maria as
they spin north and east over the southern and central
Appalachians. These should have little impact on differentiating
the wx overnight from that of the past few. As such, expect a
decent ridge to valley temperature difference through the night
with areas of fog developing in the valleys - locally dense near
the rivers and other bodies of water. The fog should be similar to
how it was Monday morning and not quite as thick as it had been
late last week and into the weekend. Even so, that will be
something to watch through the late hours of the night.
Temperatures are currently in the low to mid 70s with dewpoints
running in the low to mid 60s most places amid light and variable
winds. The grids have been updated for current T/Td/Sky obs and
trends. These have been sent to the NDFD and web servers.

&&

.SHORT TERM...(This evening through Tuesday night)
Issued at 300 PM EDT MON SEP 25 2017

Upper ridging continues to hold strong from New England through the
Tennessee Valley as Hurricane Maria sits off the mid-Atlantic coast
with another weak low across the Gulf coast. These latter features
will bring additional cirrus cloud cover through this afternoon and
into this evening before drier air advects into eastern Kentucky in
the upper levels later this evening into tonight. Temperatures will
continue to warm into the mid-upper 80s this afternoon as north to
northeast winds keep dewpoints in the upper 50s to lower 60s.

Clearing skies and light winds will promote typical valley fog later
tonight into Tuesday morning as temperatures dip into the upper 50s
while ridges remain in the low-mid 60s. Anomalous warmth will
continue Tuesday with only subtle weakening of the synoptic ridge
locally, allowing for temperatures in the mid-upper 80s once again.
Northern stream energy from the northern Great Lakes into Ontario
will further dampen long-residence ridging, but persistence will
once again spell the forecast for Tuesday night with a similar
ridge/valley temperature split and areas of valley fog.

.LONG TERM...(Wednesday through Monday)
Issued at 300 PM EDT MON SEP 25 2017

The extended portion of the forecast begins on Wednesday with the jet
stream largely positioned over the northern CONUS. While a closed
low seems to become cut off over the southwest and Hurricane
Maria just off NC coast, ridging largely remains over the the mid
and lower MS Valley as well as into the TN Valley. The only other
threat of precip remains with the storm track over the northern
CONUS. The pattern along with the period of dry conditions that
have persisted, a low chance of measurable precip is likely to
persist.

The northern stream at this point remains unable to push a feature
through the lower OH Valley that will bring a significant rainfall
at this point. The two troughs dropping south on Wednesday and
Saturday significantly shear out and dry out as they approach the
Appalachian Range. This is confirmed in the latest Euro and GFS
runs. At this point, the main impact from these will only be an
increase in cloud cover. This dry trend is confirmed with the
Super Blend showing a dry forecast through the extended. Even into
Monday, the newest GFS and 12Z Euro run shows a dry forecast with
ridging remaining strong over the Middle Atlantic area and central
Appalachians. Thus have lowered pops for Day 7.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
ISSUED AT 135 AM EDT TUE SEP 26 2017

VFR conditions look to largely continue at all sites through the
period. Valleys will continue to see fog development overnight,
resulting in locally MVFR or worse visibilities through the early
morning hours. Have elected to only keep a MVFR tempo at SME late
tonight in maintaining a mainly persistence based forecast for
next 24 hours. Fog will dissipate through the morning and make way
for mostly clear VFR conditions, save some passing high cirrus.
Winds will be light and variable through the period.

&&

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

$$

UPDATE...GREIF
SHORT TERM...GUSEMAN
LONG TERM...SHALLENBERGER
AVIATION...JMW



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