Area forecast discussion
National Weather Service Wilmington Ohio
921 am EDT Thursday may 23 2013
Synopsis...
as an upper level trough moves east through the Great Lakes...rain
showers will develop through the day today. A cold front will
move south through the region tonight...with cool and dry air
moving in from the north through Friday. High pressure will build
in through Saturday.
&&
Near term /until 6 PM this evening/...
showers continue to develop and move northeast across the eastern
part of the forecast area. These should move out of the area over
the next couple of hours. Next round of showers ahead of a
vigorous short wave and approaching cold front are already moving
into the northwest counties. Expect coverage to increase late in
the morning into the afternoon. Appears that there could be a
fairly well defined band of showers and possibly embedded
thunderstorms ahead of the cold front that sweeps across the
region during the afternoon with scattered activity still possible
just about anywhere outside the band. Have made some adjustments
to account for timing but overall idea of the forecast remains
pretty much the same.
&&
Short term /6 PM this evening through Saturday night/...
subsidence will begin in earnest behind the cold front on Thursday
night...with a switch to northerly winds allowing for cold
advection to begin at the surface. The min temperature forecast brings
the entire County Warning Area into the lower to middle 40s...with temperatures near
40 (or even around 38-39) in the far northern counties.
Surface high pressure should be centered over the region on
Friday...and this air mass appears quite dry. 850mb temperatures will
also be at their coldest on Friday...leading to a rather cool maximum
temperature forecast that keeps the entire County Warning Area in the lower to middle
60s.
Although the surface will still be in an area of high pressure by
Friday night...the upper flow will switch to the
northwest. The surface high is forecast to weaken by
Saturday...but the impact of upstream moisture aloft looks
somewhat uncertain. Some models continue to allow for a narrow
strip of quantitative precipitation forecast by Saturday afternoon and evening...mainly in the SW
County Warning Area...but this would have to fall through a very dry air mass in
the lowest several hundred mb. In fact...at the time of
precipitation...GFS soundings show cloud bases of at least 7000
feet. Keeping the forecast dry appears the better option for
now...with the surface high and dry air arguing against much of an
impact from whatever may be coming in on the northwest flow.
&&
Long term /Sunday through Wednesday/...
GFS is still showing these 500 mb disturbances undercutting the ridge
and nosing into the region Monday/Tuesday where European is somewhat
similar with an elevated convergent layer but much further
southwest and out of County Warning Area.
Surface high moves offshore early next week with drying southeast
surface winds over the Ohio Valley. Upper level flow is showing a
broadening of the 500 mb ridge as it moves over the eastern third of the
country. Have increased the chances for middle level disturbances to
undercut the ridge at this time but keep the threat for showers low
at 20% towards the middle of next week.
Expect a gradual warmup each day...starting in the upper 60s to
around 70 Saturday...warming to near 80/low 80s by Wednesday. PM lows will
be comfortably cool in the 40s through Monday morning under a dry
airmass and then warm to the climatological norms in the middle 50s by
middle week.
&&
Aviation /13z Thursday through Monday/...
upper level low centered over the western Great Lakes this morning
will pivot southeast across our region through the day. This
feature will be followed by a more vigorous disturbance in the
northwest flow aloft and will be associated with a stronger cold
front which is forecast to pass southeast across the taf sites
late this afternoon into this evening.
From late this morning into this afternoon...large scale ascent
associated with the main upper low will combined with daytime
heating/instability to produce showers. Can not rule out some
embedded thunder...but this will be too sporadic to pinpoint in
the tafs at this time so have left out. Showers should become a
little heavier out ahead of the secondary cold front this
afternoon and evening. And with moistening low levels...have gone
with predominant MVFR conditions.
For tonight...cold front will slide southeast and will result in
winds switching to the north...which will become gusty around 25
knots. Dilemma immediately behind the cold front is how low
ceilings will drop in the cold air advection pattern. Some deterministic and
ensembles suggest that ceilings could drop into IFR for a
time...especially up in the kcmh/klck area. Have kept ceilings in
the 1000-1500 range...except for kcmh/klck where ceilings will be
dropped to IFR for a time...around 8 hundred feet. Otherwise...once
the secondary disturbance passes southeast...much drier air will
filter into the region under strong subsidence between 09z and
12z. As such...any low level stratus should scour out and/or push
southeast away from the region...leaving mostly clear skies by 12z
Friday.
Outlook...no significant weather expected.
&&
Iln watches/warnings/advisories...
Ohio...none.
Kentucky...none.
In...none.
&&
$$
Synopsis...hatzos
near term...
short term...hatzos
long term...franks
aviation...Hickman
