Scientific Forecaster Discussion
fxus61 Kiln 251051
Area forecast discussion
National Weather Service Wilmington Ohio
651 am EDT sun Aug 25 2019
surface high pressure will drift away from the region today with
moisture increasing from the south by late tonight. Widespread
showers are expected Monday with precipitation chances lingering
through Tuesday. Drier and cooler conditions are expected past
Near term /through tonight/...
tranquil weather will once again persist through the entirety
of the near term period, with seasonably warm temperatures
expected for the day today. Highs will generally top out in the
Surface high pressure centered over the eastern Great Lakes will
drift further away from the Ohio Valley through the day as the
mid/upper level ridge axis traverses the region as well. This
will initiate stronger moisture advection into the area --
initially only in the upper levels in the form of denser/thicker
cirrus which will gradually overspreads the local area from
the south and west throughout the day.
Any precipitation chances will hold off until later tonight.
Short term /Monday/...
although the near term period will be a quiet one, the same
cannot be said about the short term period. Past midnight
tonight, the nosing of a seasonably modest low level jet (courtesy of
850mb-925mb winds of about 30kts) will allow for a tremendous
moisture transport to evolve into initially the southern and
western third or so of the iln forecast area through The Heart of the
overnight period. During this time period, precipitable waters will go from
about 1" to nearly 2" in only an 8-10 hour period (especially
for the tri-state area). This will initially manifest itself in
an increase in cloud cover, with progressively lower and lower
cigs to move in from the southwest in the predawn hours on
Monday. The rapid saturation of the profile, in conjunction with
midlevel energy progressing northeast from the Tennessee Valley
to the Ohio Valley, will allow for widespread showers to
overspread the iln forecast area Monday morning into the afternoon. While
an isolated rumble of thunder cannot be completely ruled out,
the poor lapse rates and nearly saturated profile will likely
keep thunder limited -- even during the typical diurnally-
favored time period in the afternoon. Have seen an uptick trend
in precipitation coverage and amounts in several deterministic
and ensemble solutions for the Monday time period (with the
operational GFS on the lower end of the gefs quantitative precipitation forecast envelope) --
so have increased pops and quantitative precipitation forecast accordingly to trend toward a
more widespread rain event.
The onset of precipitation will likely be occurring before
daybreak across parts of northern Kentucky and perhaps extreme
southeastern Indiana into southwestern Ohio. There are some
subtle timing differences in the various solutions regarding
exactly how quickly the precipitation moves in and how fast the
initially drier profile is able to be overcome. Nevertheless,
will see widespread showers overspreading the local area through
Monday morning and afternoon -- with indications of amounts
between 0.50"-1.0" very likely near and west of the I-75
corridor into parts of north-central Kentucky by Monday evening. The
heaviest and most widespread activity will initially be focused
across the tri-state area before progressing North/East through
the day. Rainfall amounts are likely to taper somewhat from SW
to NE -- with parts of central Ohio more likely to see around
0.25-0.50" through the day (specifically afternoon/evening for
With the overspreading of thicker cirrus and cloud cover by late
tonight, will see generally warmer temperatures than has been
the case the past several overnight periods as lows only bottom
out in the low to mid 60s from NE to SW. Highs on Monday will be
held considerably below seasonal norms with the expectation for
thick cloud cover and widespread showers throughout nearly the
entire daytime period for some spots. Temps will top out in the
lows 70s (sw/w) to the mid/upper 70s (ne/e).
Although a gradual tapering off of the precipitation is expected
toward Monday evening, will likely see some scattered showers
linger in parts of the iln forecast area even through Monday night before a
cold front approaches with renewed precipitation chances Tuesday
Long term /Monday night through Saturday/...
a broad upper level trough will remain across the Great Lakes region
through much of the week. Mid level short wave energy will rotate
through the base of the trough Monday night into Tuesday, helping to
push an associated cold front east across the Ohio Valley. This will
lead to an increasing chance of showers through the day on Tuesday.
Instability will be fairly marginal, but with increasing wind fields
through the day, will allow for at least a chance for some embedded
thunderstorms. Highs on Tuesday will be in the upper 70s to lower
Drier air will try to move in behind the front Tuesday night but
some additional mid level short wave energy will pivot across the
region through the day on Wednesday. This may be enough to produce a
few showers through the day but think the wetter GFS may be
overdone. Will therefore maintain a dry forecast for Wednesday at
this time. Highs on Wednesday will again be in the upper 70s to
Surface high pressure will build east across the Ohio Valley
Thursday into Friday. This will result in dry conditions. A
weakening frontal boundary will push south into the region Friday
night into Saturday, leading to a slight chance of showers.
Temperatures through the remainder of the long term period will
remain slightly below normal with highs in the mid 70s to lower 80s
for Thursday through Saturday.
Aviation /12z Sunday through Thursday/...
other than a few passing cirrus, mainly clear skies are expected
through the morning hours. A few VFR cu may again
develop/expand this afternoon as thicker cirrus gradually
overspreads the region from the southwest through the day.
Between 06z-12z, a tremendous increase in deep layer moisture
will allow for rapid saturation of the profile progressively
from southwest to northeast early Monday morning. This will
occur coincident with a shield of rain showers fcst to move north into
the southern Ohio Valley by daybreak. As of right now, this is
only included in the kcvg and kluk fcsts late in the period.
Expect IFR cigs and potentially MVFR vsbys to overspread the
southern terminals through Monday morning before these
restrictions spread further North/East through the afternoon
hours. With a nearly saturated profile developing in the low
levels, do think that cigs between 800-1200ft will evolve for at
least brief stretches Monday morning (in a several hour period
after 12z) -- especially for kcvg, kluk, and potentially even
Light northeasterly winds will go more easterly later today but
remain generally 10kts or less. A shift to more east-
southeasterly will evolve tonight before relaxing somewhat and
going more southeasterly Monday morning.
Outlook...IFR cigs possible Monday. Thunderstorms are possible
on Monday and Tuesday.