Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Jackson Kentucky
1135 am EDT Thursday Jul 30 2015
issued at 1135 am EDT Thursday Jul 30 2015
The cold front continues to exit to the southeast and toward the
crest of the Appalachians. Drier air has begun to filter in from
the northwest behind the front as surface high pressure builds into
the Ohio Valley. With the front departing...the threat for any
additional showers or convection has ended. Low clouds near the Virginia
border are also beginning to lift into cumulus and mix out...from the
Tennessee Valley region and from the northwest. Probability of precipitation have been adjusted
accordingly... with remaining hourly grids also freshened up based
on recent observations...radar...and satellite trends.
Update issued at 911 am EDT Thursday Jul 30 2015
Hourly probability of precipitation...as well as temperature and dewpoints were updated
based on recent observations and radar trends. A cold front
continues to work southeast across the region at this time. Behind this
front...high pressure is building into the lower Ohio Valley
region...with drier air working into the lower Ohio Valley region.
Overall...very little changes were needed at this time.
Update issued at 722 am EDT Thursday Jul 30 2015
Clouds were a bit more extensive than originally expected for this
morning...and have slowed the clearing process slightly.
Short term...(today through friday)
issued at 357 am EDT Thursday Jul 30 2015
Early this morning a cold front was positioned from near kbna to
kcmh...and was moving southeast. It will pass through the jkl
forecast area this morning. It will arrive at an unfavorable time
for convective development...but it will not be ruled out...and a
20 percent pop was used. Behind the front...drier air will arrive
as high pressure builds in from the west. This will bring mainly
clear skies tonight and Friday...and allow for cooler low temperatures on
Friday morning...with some valleys probably falling into the 50s.
Long term...(friday through wednesday)
issued at 357 am EDT Thursday Jul 30 2015
The models are in broad agreement with respect to the main features
and longwave pattern aloft during the extended portion of the
forecast. They all depict a deepening trough over the eastern half
of the continent through the weekend. Initially the energy
associated with this stays well to the north...running through the
Great Lakes...but a strengthening wave will move into the Ohio
Valley in northwest flow by midday Sunday. This wave passes through
east Kentucky by early Monday...though additional bits of energy
will trail behind into Tuesday morning. The model spread increases
through middle week as the GFS and Canadian models move the Canadian
trough to the east a bit quicker than the European model (ecmwf). Despite this...
though...the latter model does bring higher heights into Kentucky
for Wednesday as its Hudson Bay upper low is more shallow than the
others. Given the model agreement through the bulk of the period and
greater uncertainty later on will favor a general blend solution.
Sensible weather will feature a continued respite from the worst
humidity of the past several days running into the weekend before
the higher moisture returns for the start of next week. Temperatures
will be near normal for the extended portion of the forecast. Surface
high pressure will keep most of the convection at Bay through Sunday
before the approach of another front helps to trigger more in the
way of diurnally driven showers and storms. This boundary will stall
nearby through at least middle week...keeping a threat of showers or
storms in the forecast from Monday afternoon through Wednesday.
The CR grid blend came in reasonably well with the bulk of any
adjustments made to the probability of precipitation and sky grids to better reflect the
diurnal cycle. As for temperatures...did adjust the lows a bit each
night to capture minor to moderate terrain effects.
Aviation...(for the 12z tafs through 12z Friday morning)
issued at 722 am EDT Thursday Jul 30 2015
Conditions varied from LIFR to VFR early this morning....but were
mainly IFR and MVFR. Improvement will occur generally from northwest to
southeast today...with VFR expected just about everywhere early this
afternoon. Good conditions should then last through most of the
period...with just a bit of valley fog late tonight.