Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington Ohio
130 am EDT Thursday may 7 2015
a warm front will lift north into the Great Lakes placing the Ohio
Valley in a warm airmass. Daytime high temperatures will be around
15 degrees above normal through the end of the week...with highs
generally in the middle to upper 80s. An isolated afternoon thunderstorm
can not be ruled out but for the most part...dry conditions are
expected into Friday. An area of low pressure will slowly
approach the Ohio Valley this weekend... providing a return of
scattered showers and thunderstorms before a cold front moves
through early next week.
Near term /through today/...
showers have long since dissipated across the forecast area...and
clouds have mostly followed suit...with clear to mostly clear
conditions expected through the overnight hours. Some middle clouds
may drift in from the south...where 700mb moisture is a little bit
thicker than elsewhere in the region.
There appeared to be little reason to change the temperature
forecast...with lows around 60 degrees expected. However...some
patchy fog was added into the northern sections of the forecast
area. Fairly light winds and clear skies will combine with the
slightly greater low-level moisture (dewpoints in the upper 50s)
to allow for some fog to develop by early morning. However...with
the warmer starting point (and the front now a little further
north than it was yesterday)...the chances for any dense fog
appear greater closer to the Lake Erie and across northern Indiana
Previous discussion >
amplified middle level flow pattern with a trough over the west and a
ridge oriented from the Ohio Valley through the western Great
Lakes. This ridge axis to build a little east becoming centered
over the region by Thursday morning. Isolated showers and thunderstorms
have developed across iln/S forecast area northern counties in vicinity of east-west oriented surface
front where marginal instability exists. Another area of isolated showers/
thunderstorms has developed across northern Kentucky. These storms will be short
lived with lack of shear they will go up and down quickly with all
convection expected to end early this evening.
Surface front across our north to shift north into the Great Lakes with
diurnally driven cumulus clouds dissipating...giving way to mostly
clear skies overnight. Mild temperatures to continue with lows
from the upper 50s north to near 60 south.
Short term /tonight through Friday night/...
middle level ridge axis to remain over the area Thursday and then
slide slightly east Friday. This will allow for continued above
normal temperatures. Highs look to be at or slightly more than
15 degrees above normal for Thursday and Friday. Lows will
continue to be mild...in the lower and middle 60s Thursday
With the lack of significant forcing expect generally dry
conditions Thursday. Can not rule out an isolated shower/thunderstorm
in the far west in afternoon but any convection that develops will be
short lived. As the middle level ridge shifts a little east more
favorable instability develops and there will be a better chance of
convective development. Have limited probability of precipitation to slight chance in the
west Friday afternoon into Friday night.
Long term /Saturday through Wednesday/...
this period characterized by anomalous warmth on the weekend...the
passage of a weather system with good shower/thunderstorm
threats...and a brief transition to much cooler weather for the
middle of next week.
At 12z on Saturday...flow still quite amplified over the noam
continent and adjacent waters. Persistent cutoff low off the SC
coast...trapped within/underneath large scale ridging centered along
the eastern Seaboard...downstream from deep/longwave trough centered in
The Rockies with a closed low over nm/Utah. Sharp ridging along the
Sat/sun put the Ohio Valley on the eastern fringe of modest southwesterly
middle/upper level flow on the east side of the slowly advancing
western/cntl Continental U.S. Longwave trough. 925mb temperatures continue to hover around
20c both days which should yield more low/middle 80s...with dewpoints
incrementally rising into the lower 60s adding dose of summertime
mugginess to the air. Synoptic forcing quite weak...but
nonzero...with weak shortwave activity /likely remnant mesoscale convective vortex/S from
plains convection/ traversing from western Kentucky/ind into mich through both
days. So think there will be rain showers/storms on both days /esp western Ohio
and southeastern ind/ but likely loosely focused with a noted diurnal
component to the intensity/coverage. Not much confidence to add
detail to this part of the forecast in the rain chance dept. Neither
day will be a washout...in fact...the bulk of both days should be
Later Sunday night and especially Monday....closed low begins to
eject northeast into the western Great Lakes with Ohio Valley still
firmly in the warm sector. Moisture transport magnitudes/focus
should also be on the increase as the day wears on and into Monday
evening. Continued with 50-65% rain chances this period to coincide with
the ensemble-driven signals in this time frame. Likely still a very
warm day on Monday especially further east where moisture and clouds
will be less. Tropospheric flow /unidirectional southwesterly/ also increases
so will need to watch for lower-end severe threat if forcing/instability can
be juxtaposed sufficiently sometime Monday aftn/eve.
Closed low begins to shear downstream Monday night and Tuesday as
cold front sweeps through. Unfavorable timing for widespread precipitation so
keeping rain chances in high chance area at this time range. Turning
cooler through the day on Tuesday with threat for a few rain showers...but
expect mainly dry conditions. High pressure builds in Wednesday as a
much cooler airmass builds in...with deterministic 850 mb temperatures
approaching 0c in parts of the Great Lakes on Wednesday. Temperatures on
Wednesday right now look low-middle 60s...quite a bit below
normal...and looks like cooler weather will linger into the end of next
Aviation /06z Thursday through Monday/...
we may see a few ac drift across the area from time to time this
morning but for the most part expect mainly clear skies. With
light winds...some patchy fog development will be possible through
the pre dawn hours. This will most likely affect kluk where some IFR
visibility restrictions will be possible toward daybreak.
Middle level ridging overhead will slowly slide east through this
afternoon. This will help suppress shower/thunderstorm activity but
it will still be tough to rule out some isolated activity given
some developing instability through the day. Chance is low enough
though to leave any mention out of the tafs at this time.
Outlook...occasional rounds of showers and thunderstorms will move
through the area from Saturday through Monday night.