Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Jackson Kentucky
1054 am EDT Sat Sep 5 2015
issued at 1054 am EDT Sat Sep 5 2015
Fog has burned off this morning...with another hot day in
store...as temperatures make their way to around the 90 degree
mark once again. Isolated to scattered convection still looks
supported given the steep low level rates that will be in
place...although coverage continues to look to be more restricted
to the higher terrain this afternoon. Freshened up the hourly
weather elements based on the latest trends in observations...
otherwise the forecast is well on track. Updates have been sent.
Update issued at 654 am EDT Sat Sep 5 2015
The primary weather issue this morning will be the patchy to areas
of dense fog. Based off the fog channel best concentration is
across the southeast and the usual River Valley. No major changes made
this morning to the grids...but a few minor updates to
temperatures/dews/winds with latest observation and trends.
Short term...(today through sunday)
issued at 312 am EDT Sat Sep 5 2015
WSR-88D radar is quiet this morning...but still seeing a overnight
outflow boundary moving southeast closer to the Virginia border. Overall this
should have little affect...but could stifle some areas from
completely decoupling. This could limit the fog production in
spots this morning...but still think patchy dense fog will be
possible particularly in the river valleys. This fog will clear
out after sunrise and we will be left with mostly sunny conditions
across eastern Kentucky. This will set the stage for yet another warm
and humid day across the region with temperatures in the upper 80s and
lower 90s once again.
Also given unstable airmass in place would once again expect
scattered to isolated storms to develop in the afternoon hours.
Right now kept close to the previous forecast with best chances
along the Tennessee/Virginia border...where topo should help with firing off
storms. This seems reasonable given the cams hinting at this area
on both the sseo and WRF-arw ensembles. The question will be
where do these storms drift and where do the outflows move.
Yesterday this was a key component to the overall development of
these storms particularly in the evening...since we have not
discernible upper level support or lifting mechanism. Given the
more mesoscale nature of this this will have to be looked at
closer through the day today. This will set the stage for another
night of fog potential mainly in the valleys. Fog could be more
dense in those locations that are able to see rainfall.
Sunday did opt to put a isolated pop along the Tennessee/Virginia border
locations and stuck close to the blend at this point. Overall
thinking most spots will stay dry given the isolated nature. Temperatures
for Sunday will once again be in the upper 80s to lower 90s.
Long term...(sunday night through friday)
issued at 410 am EDT Sat Sep 5 2015
The period will begin with a broad upper level low/trough across
the southeastern Continental U.S. And an area of ridging from the Atlantic
west into the Midwest and then south into the Southern Plains and
northern Mexico. Meanwhile...another trough is expected to be
moving across the western Continental U.S. With an associated upper level
low over Saskatchewan.
Sunday night through Monday evening...the the upper level low
initially over the southeastern Continental U.S. Should meander to the
central and eastern Gulf of Mexico while an area of ridging
remains in place from northern Mexico northeast into the arklatex
region and then east to the Atlantic. The appalachian region will
remain in an area of slightly lower heights between the two
centers of the ridging...northeast of Bermuda and over the
Southern Plains. Also during this time...the northern and
stronger upper level low will move from Saskatchewan to Manitoba.
The from Monday night into midweek...heights should fall across
the Great Lakes region and the Ohio Valley as the northern upper
level low tracks toward Hudson Bay. This will leave generally
western flow with a broad trough from the Pacific northwest into
the Great Lakes. Models differ with heights from the Ohio Valley
south into the Gulf of Mexico...but across that region...a trough
or weakness in the upper level should exist between ridging
centered over northern Mexico and the southwestern Continental U.S. And a
ridge centered over the western Atlantic. At the surface...a cold
front will drop into the Ohio Valley at midweek.
From midweek through the end of the period...a series of
shortwaves will carve out a trough from Hudson Bay south into the
plains on Thursday and then into the MS valley region and approach the
eastern Continental U.S. Late in the period. Additional shortwaves should also
work across the Ohio Valley from Wednesday into Friday. The developing
trough should push a stronger cold front toward the commonwealth
at the end of the period. This front...however...should not cross
east Kentucky until Friday night or next Sat.
As for chances for convection...they will initially be better
over the higher terrain near the Virginia and Tennessee border on Monday and Tuesday
afternoon where heights will be slightly lower and differential
heating across the Cumberland mountains and northern Cumberland Plateau
may serve as triggers for isolated convection. As the pattern
begins to change during the middle part of the week...Tuesday night
through Thursday...and as the first boundary moves into the
area...chances for convection will increase across the entire
area. Even then...coverage should be mainly scattered. The weather
will remain unsettled through the end of the period as the upper
level trough and a cold front approach.
As for temperatures...they should average above normal for highs
and lows with a somewhat limited diurnal range due to a moist
airmass in place and associated clouds and precipitation from time to
Aviation...(for the 12z tafs through 12z Sunday morning)
issued at 720 am EDT Sat Sep 5 2015
Biggest issue this morning is the areas of fog with a few sites
going MVFR to LIFR. Fog will lift and dissipate after sunrise this
morning and remove the visible/ceiling restrictions. Airmass thunderstorms
will once again be possible this afternoon and will mainly pop up
toward the Tennessee/Virginia border. Therefore kept with thunderstorms in the vicinity at all
the sites in the afternoon hours. Winds are expected to be
light...but if a storm hits a taf site could see brief gusty winds
and visible/ceiling restrictions.