Area Forecast Discussion
Issued by NWS Jackson, KY

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671
FXUS63 KJKL 221630
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1230 PM EDT Tue May 22 2018

.UPDATE...
Issued at 1230 PM EDT TUE MAY 22 2018

Forecast is on track early this afternoon. Convection is
beginning to fire across the area as some type of lingering
boundary or feature slides slowly southeast into the area. This is
providing a focus for additional convection and expectations are
that this feature will escort activity through and out of the area
by later this evening. While can not rule out a few strong
storms, or even an isolated severe storm or two, feel main threat
will be heavy rain and the potential of some localized flooding
in area that are prone, e.g. low water crossings, etc. Updated the
grids to bring in line with current hourly trends and the zones
to freshen up the wording.

UPDATE Issued at 759 AM EDT TUE MAY 22 2018

Issued an update to the forecast to input the latest observations
and trend them into the mid morning hours. Also adjusted pops
slightly to be more representative of the current conditions with
a few showers popping up to the west. A new zfp has already been
issued for this update.

&&

.SHORT TERM...(Today through Wednesday)
Issued at 348 AM EDT TUE MAY 22 2018

Current conditions across the area feature some mid and upper
level cloud cover moving through the area. In addition, the last
of a few showers will move northeast out of the Bluegrass area.
With the cloud cover moving through, fog development has been
halted. A few spots in the south with some clearing will see some
visibility drop but this is the exception. The overall pattern
indicates a continued return flow with ample moisture continuing
to stream north into the OH Valley. This will be the case heading
into the day today. Model soundings indicate a continued PWAT
values of 1.65. Though as been the case for the pas several days,
the lack of a good impulse tracking by and organizing this
convection, the activity remains largely scattered despite the
amount of moisture being pumped into the region. Thus will go for
a good chance heading into today. A weakened front from the north
will begin push southeast through the day. Convection will
intensify a bit along this washed out boundary as it pushed
southeast. Will keep pop chances going through the day today and
into tonight. Despite the scattered nature of the showers and
storms, this is still a saturated air mass and any storm can put
down enough rain to cause some minor flooding issues. For tonight,
good saturation of the boundary layer will allow for fog
development with ongoing showers through the night slowly pushing
southeast. Behind the boundary, the hint of some clearing as some
dry air attempts to enter area will allow for some more widespread
fog to develop.

Heading into the day on Wednesday, the front will have pushed
southeast and slow along the TN and VA border. Will expect some
shower and a few thunderstorms to develop along the boundary and
especially in the higher terrain. Meanwhile clearing skies to the
northwest will allow temps to rebound into the low 80s. This is
still above normal despite the cooler air moving into the area.

.LONG TERM...(Wednesday night through Monday)
Issued at 355 AM EDT TUE MAY 22 2018

The models are in fair agreement with the longwave pattern and major
features aloft through the extended portion of the forecast. They
all depict a relatively weak full latitude ridge over the region to
start this portion of the forecast. This ridge weakens and fades out
by the end of the work week under twin assault from the northern
stream and a potential tropical system to the south. The northern
stream will return a flow of energy into the Great Lakes region to
start the weekend while to the south heights will be falling due to
the developing upper low along the central Gulf Coast. Some energy
associated with this low will start to ooze into Kentucky late in
the weekend and to start the next week. The main factor in the model
differences late in the period revolve around the depth and
development of this southern low with the ECMWF more aggressive than
the GFS having a mid level low somewhat deeper and more westerly
than the GFS. Will favor a blended solution here with monitoring
needed to see if the deeper scenario of the ECMWF starts to pan out
and work better with the predictions out of the NHC - in time.

Sensible weather will feature a respite from the afternoon/evening
showers and storms - and their periodic deluges - from Wednesday
night through Friday. However, after that, return flow moisture and
potential for tropical interaction will put us right back in an
environment of potential heavy rains from diurnally enhanced showers
and storms for Friday night through Monday. This will be more so the
case should the ECMWF solution pan out when compared to the GFS, but
both suggest a wet and active weekend and beyond. For now we will
need to make the most of the dry patch to close out the work week.

Made mainly terrain based adjustments to the lows each night during
the work week from the SuperBlend starting point with enough dry air
initially suggesting small to moderate ridge and valley temperature
splits. Did not deviate far from the blended PoPs into the weekend,
though did beef them up each afternoon to better match the
anticipated diurnal impact on this upcoming pattern.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
ISSUED AT 759 AM EDT TUE MAY 22 2018

Expect a few instances of MVFR and IFR conditions this morning as
the left over valley fog lingers into mid morning. This fog will
burn off by mid morning as some showers and thunderstorms will
develop and move into the area by midday. Scattered activity will
continue into tonight. A weak front will push to the southeast as
sky cover will slowly clear from the northwest. With this, fog
will begin to form in the valleys late tonight and persist into
the dawn hours. Winds will remain light through the period outside
of thunderstorms.

&&

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

&&

$$

UPDATE...RAY
SHORT TERM...SHALLENBERGER
LONG TERM...GREIF
AVIATION...SHALLENBERGER



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