Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 230500

National Weather Service Jackson KY
100 AM EDT Thu Mar 23 2017

Issued at 100 AM EDT THU MAR 23 2017

Surface analysis at this overnight hour shows surface high
pressure is centered along and near Lake Erie. We remain under
the influence of this surface high with light winds out of the NE,
however, the deeper valley sites have been able to decouple. GOES
16 IR data does show some high clouds are streaming across, with
the overall best coverage in the Lake Cumberland region.
Therefore think the Freeze Warning remains reasonable this hour.
Otherwise forecast is on track and therefore only minor changes
are needed to deal with the latest obs.

UPDATE Issued at 1000 PM EDT WED MAR 22 2017

Forecast looks on track tonight, so only update was to remove
evening wording from the products. Otherwise, forecast is in good
shape and no changes needed to ongoing freeze warning headlines.


.SHORT TERM...(This evening through Thursday night)
Issued at 335 PM EDT WED MAR 22 2017

High pressure anchored across Lake Michigan will drift southeast
this evening, allowing for a few cirrus clouds to gradually shift
across south central Kentucky. Increasing relative humidity values
will ensue as temperatures cool into the upper 30s across the
Bluegrass region and 40s elsewhere early this evening, while
northeast winds diminish to near or below 5 mph as the pressure
gradient relaxes. Fire weather concerns will thus come to an end
by dusk.

With clear skies for a period this evening and tonight across the
Big Sandy region of eastern into northeast Kentucky, temperatures
will quickly fall through the 30s and into the 20s. A Freeze Warning
will be in effect at 11 pm through 10 pm Thursday morning as
temperatures below 30 degrees look to be a sure bet for a few hours,
given dewpoints this afternoon in the teens and efficient
radiational cooling. While low temperatures should fall into the
upper 20s to low 30s for much of eastern Kentucky, valley locales,
especially in far eastern into northeastern Kentucky, will likely
fall into the low to mid 20s.

Moisture will increase Thursday as surface ridging shifts across the
Appalachians and upper ridging slides overhead aloft. Precipitation
looks to remain northwest of the Bluegrass region later in the
afternoon toward evening nearer a warm front lifting north ahead of
a surface low ejecting out of the Front Range. Forecast soundings
show subsidence being far too strong to support anything locally,
despite deep layer moistening and precipitable water values
approaching 0.75 to 1 inch. May still see RH values approach 25-30
percent across far eastern Kentucky before moisture advection takes
place into the afternoon as winds veer southerly near 5-10 mph.
Increasing heights/thicknesses underneath the approaching ridge will
warm temperatures into the 60s. Warm air advection Thursday
evening/night will continue, leading to a much warmer night in the
low-mid 40s.

.LONG TERM...(Friday through Wednesday)
Issued at 335 PM EDT WED MAR 22 2017

The models are in fairly good agreement through the weekend, but
then begin to diverge as we move into next week.

Dry warm weather will be on tap for Friday with south to southwest
flow ahead of an upper level low pressure system and associated
surface low over the southern plains. This system will move
northeast towards the Great Lakes over the weekend, bringing shower
and thunderstorm chances to eastern KY. The trend has been to slow
the arrival of shower chances for Saturday afternoon, and will
continue with this idea. Much of Saturday looks to be dry, with
shower chances becoming likely during the evening, with categorical
probabilities overnight, along with a slight chance of
thunderstorms. The high rain probabilities will persist into Sunday
morning, with shower and thunderstorm chances decreasing from west
to east during the day Sunday. With the track of the low to our
west, temperatures will remain well above normal through the weekend.

Behind the weekend system an upper level trough and associated
surface low will emerge from the southern plains and again move
northeast early next week. This will bring shower and possibly
thunderstorm chances back to the area mainly late Monday, with
shower chances lingering into at least Tuesday. However, there is
not good agreement on the evolution of the upper air pattern for the
early to middle part of next week. The 12Z GFS phases the southern
stream system already noted above with a northern wave, with the
result being pronounced troughing from the Great Lakes into the OH
Valley. The 12Z ECMWF quickly moves the southern stream system
through with no phasing and much less overall troughing. The result
is that the GFS allows much cooler air to push into eastern KY by
mid week, while the ECMWF keeps temperatures much more mild. In fact
by 18Z Wednesday the GFS shows 850 mb temperatures anywhere from -2
to 3 C across the area, while the ECMWF has temperatures generally
around 10 C. The standard model blend leans towards a solution that
is warmer than the 12Z operational GFS and this makes sense
considering the operational GFS is on the cool side of the GFS
ensemble members, and several degrees cooler than the GFS ensemble


.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)

VFR conditions and light winds will be seen over the next 24 to 36
hours. The light winds will transition from northeast tonight to
south during the day tomorrow.


Freeze Warning until 10 AM EDT this morning for KYZ044-050>052-



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