Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington Ohio
935 PM EDT Wednesday Sep 17 2014
high pressure will extend across the region through the end of the
week. A cold front will move through on Sunday.
Near term /until 6 am Thursday morning/...
early evening water vapor loops clearly show weak/subtle shortwave
trough over southeastern Illinois/southern ind shifting quickly southeast into the
middle Ohio Valley and weakening. Areas of middle cloud are shifting
through southern ind/southern Ohio/northern Kentucky but plenty of clearing in between.
Upstream in eastern Illinois/western there is more middle cloud but this is
breaking up. Will keep a sky cover somewhere between 20-50 percent
/highest in the south/ much of the night for these transient middle
cloud decks attendant to the weak wave shifting through. Diurnal
cumulus has dissipated and winds are calm with surface hi in
control. T/dew point spreads are variable across the area ranging from 6f
to 13f at 01z...and given forecast soundings think the valleys will fog
tonight rather deeply with shallow fog other areas. Added this to
the gridded forecast emphasizing valleys/drainage areas. More
widespread/dense fog signal is well southwest of the iln forecast area
per nwp but can/T rule out a pocket or two here. Temperatures looked decent
at this hour with large variation from populated corridors to
rural/outlying areas...typical of a good radiational cooling
Short term /6 am Thursday morning through Friday night/...
high pressure centered over the upper Great Lakes will pass into
New England during the period. Ridging from this will extend into
the Ohio Valley through the entire short term. This will keep a
dry air mass in place with a gradual warming trend. Shaded towards
the cool side of MOS highs but went towards warmer MOS lows based
on bias trends.
Long term /Saturday through Wednesday/...
Saturday will be the warmest day of the long term period. Southerly
flow in advance of an approaching low pressure system will allow for
temperatures to climb into the upper 70s to the lower 80s. Dry
conditions are expected to be present during the day on Saturday and
into Saturday night.
A cold front approaches and moves through on Sunday. This feature
will bring showers and thunderstorms to the area on Sunday. Some
precipitation will linger across southeast portions of the forecast area Sunday
evening before tapering off across the area. An upper trough moves
through Sunday night into Monday keeping some clouds in the forecast
across the area and showers across northern portions of the forecast area on
Monday. Shower activity and most of the cloud cover dissipate
With decreasing clouds and light cool northerly winds expect
temperatures to drop down into the 40s across the entire forecast area Monday
night. High pressure will allow for dry conditions for the
remainder of the long term time frame. With continued mostly clear
skies and continued cool airmass in place expect Wednesday morning
to be the coolest morning. Went with low temperatures in the upper
30s to middle 40s across the area. At this time have confined 30s
to extreme eastern portions of the forecast area however would not rule out
more 30s across northern portions of the forecast area.
Aviation /02z Thursday through Monday/...
inherited tafs were well trended. Weak shortwave trough shifting
southeast through the middle MS valley will continue to allow a few
middle/high clouds across the southern terminals through the night but
trending downward in coverage with time. Biggest concern for
aviation will be fog potential after 06z...especially
kluk/Kiln...but all sites have at least a small possibility for
visibility restrictions in shallow fog later on. Continued with pvs
forecast idea of socking in kluk to IFR overnight in what seems
like a good River Valley drainage event if skies can remain mostly
clear as expected. Also brought visibilities down at Kiln a little lower
than pvs forecast based on winds turning northeasterly with time and
decreasing to 3kts or so...which boosts probabilities of fog based
on climatology distributions here. Expect this to be shallow and burn
off by 13z or so...with diurnal scattered cumulus dvpmnt looking likely
late morning through the afternoon under northeasterly breezes of 7-8kts at
Outlook...thunderstorms possible Sunday.