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Area forecast discussion 
National Weather Service Jackson Kentucky
353 PM EDT Tuesday Aug 4 2015

Short term...(this evening through Wednesday night)
issued at 352 PM EDT Tuesday Aug 4 2015

A nearly stationary boundary remains draped from west to east
across the central part of the forecast area. This has served as a
focus for convection this afternoon...and once again we are dealing
with some heavy rainers. We do expect this activity to dissipate
this evening...and will decrease rain chances as the evening
progresses.

The surface boundary will remain across the area for the next
couple of days...while a couple of middle/upper level short wave
troughs move east from the plains into the Ohio Valley. A rather
nebulous wave will affect the region later tonight...and have
increased rain chances again late tonight for the western part of
the area.

A second and much stronger wave will begin to affect the area
Wednesday night. While there is good model agreement on a strong
wave moving into the Ohio Valley...exactly where the heaviest rain
axis will set up is in question. However with precipitable water
increasing...the possibility for training...and the threat for
more widespread thunderstorms with heavy rain have decided to go
with a Flash Flood Watch beginning 11 PM Wednesday and running to
7 am Friday. This is for all but the most southern tier of
counties.

Long term...(thursday through tuesday)
issued at 352 PM EDT Tuesday Aug 4 2015

Models continue to come into better agreement with a modestly
amplified middle/upper level long wave pattern to start out the
extended. We find our area under the influences of northwest flow
aloft with weak embedded impulses through the middle term. Then we
finish up the extended with another respectable shortwave that moves
out of the upper Midwest and that reinforces an eastern Continental U.S. Mean
trough.

First trough is expected to move across the Ohio/Tennessee Valley regions
Wednesday night through Thursday. However...there continue to be
some significant differences at the surface. At this time ample moisture...a
relatively slow moving surface system...the potential for training and
other favorable Hydro parameters suggest that locally heavy rainfall
may become a concern from Wednesday night through late Thursday
evening. However...much will depend on the exact track of the surface
wave which the 12z GFS takes further to our south. With the more
southerly path of the GFS its axis of heaviest rainfall is...as
would be expected across The Heart of the commonwealth. The 0z European model (ecmwf)
and 12z NAM keep the storm track further north and consequently
heaviest axis of rain along and either side of the Ohio River.
Thoughts are to issue a Flash Flood Watch for the window of
concern...which will straddle the short and long term forecast
periods.

Thereafter details associated with the evolution of the pattern
remain lower confidence. As such...stayed pretty close to the
offered blended guidance. Will be increasing probability of precipitation into categorical
territory for Thursday proper. The boundary will sag southeast
behind the departing surface low and dissipate by the weekend...allowing
for mainly dry weather. Mean eastern Continental U.S. Trough will amplify again
across the Ohio Valley by early to middle next week...bringing another
frontal zone with associated weather through the area and to our
south.

&&

Aviation...(for the 18z tafs through 18z Wednesday afternoon)
issued at 124 PM EDT Tuesday Aug 4 2015

A stalled front remains in place across Kentucky. This will serve
as a focus for isolated to scattered thunderstorms late this
afternoon and evening. The chance of any specific taf site being
affected is low...and expect any storms to mainly occur across the
SW half of the forecast area. With this in mind will carry thunderstorms in the vicinity
at jkl...loz and sme for a few hours beginning at 21z. Fog is
expected to develop late tonight...reducing visibility to IFR or
worse until around 13z on Wednesday. Outside of any thunderstorms
or late night/early morning fog...VFR conditions will prevail.



&&

Jkl watches/warnings/advisories...
Flash Flood Watch from Wednesday evening through late Thursday
night for kyz044-050>052-058>060-068-069-079-080-088-104-106>120.

&&

$$

Short term...sbh
long term...ray
aviation...sbh

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