Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus61 Kiln 190546 
afdiln

Area forecast discussion
National Weather Service Wilmington Ohio
1246 am EST Tue Nov 19 2019

Synopsis...
a large upper level trough over the Great Lakes and Ohio Valley
will bring cloudy and cool conditions through the next couple
days, with some chance for drizzle or light rain, especially on
Tuesday. High pressure will move over the region on Wednesday,
offering dry weather. An enhanced chance for rain will occur on
Thursday, as low pressure tracks northeast into the Great
Lakes.

&&

Near term /until 6 am this morning/...
a zone of low level moisture on the edge of weak low level warm
air advection will result in a period of patchy drizzle and fog
as it propagates from west to east tonight. Current forecast
reflects this. Temperatures will fall into the lower to mid 30s.

&&

Short term /6 am this morning through 6 PM Wednesday/...
broad longwave trough will continue to be in place over the
Great Lakes/Ohio Valley Tuesday. Lingering low level moisture
will lead to continued cloud cover in the morning and patchy
drizzle early.

Model solutions in better agreement with mid level energy
dropping southeast from the mid MS Vly into the Ohio Valley
Tuesday aftn. This shortwave will lead to better forcing and
deeper moisture. The best threat looks over the west/southwest
during the aftn. Have increased the pops to 40 percent but these
pops may have to be bumped up. Rain from this event should be on
the light side with quantitative precipitation forecast generally a tenth of an inch or less.
Have nudged temperatures down slightly due to clouds/pcpn
Tuesday, with fcst highs from the mid 40s north to the upper 40s
south.

Trof axis to shift to the east Tuesday evening with height rises
surface ridge beginning to build in from the west overnight. Any
lingering rain in the far east will come to and end early. Clouds
look to linger through most of the night. Expect low temperatures
in the lower and middle 30s.

&&

Long term /Wednesday night through Monday/...
by Wednesday, confidence is fairly high that an amplified ridge moves
eastward into the region promoting dry and near seasonable weather
to start the long term. Saturated low levels Wednesday morning
leads to lingering areas of fog and low level clouds before breaks
in the clouds occur later in the afternoon. The window for clearing
is brief as the next upper level feature moves into the region
during the evening hours on Wednesday. While rain chances hold off
until Thursday, upper level clouds should be streaming eastward by
the evening into the overnight.

Upper level ridge axis shifts eastward on Thursday as a subtle upper
level trough moves through the Great Lakes. The trough promotes the
development of low pressure to the northwest, introducing the next
chance for rain and breezy conditions (wind gust to 30 mph at times)
starting Thursday late morning/early afternoon from the west. Winds
will be greatest during the afternoon and early evening Thursday.
Overall speed of the rain has slowed as the upper level trough has
trended weaker and the ridge more amplified over the last few days.
Scattered rain showers are forecast through the second half of the
day on Thursday with periods of light rain also possible, however,
overall quantitative precipitation forecast has trended lower as well. The cold front moves through
during the early morning hours on Friday with abnormally warm
temperatures Thursday night. Cold air advection eventually moves in
Friday morning with the front stalling south of the area.

Uncertainty in the forecast increases starting Friday morning. Most
recent operational output still diverge greatly on the placement of
the next low pressure which quickly moves into the middle Tennessee
Valley late Friday night into Saturday morning. The ecwmf is much
slower progressing the front through the area with rain chances
lingering in the south into the day on Friday. By Saturday morning,
the second area of low pressure is already pushing through the Ohio
Valley with a broad shield of precipitation spreading across the
entire area. With the further north track, all precipitation is
liquid. However, the CMC/GFS are further south, but the CMC is more
in the middle with low pressure tracking southeast of the area. This
keeps cooler air in place, possibly resulting in a rain-snow mix
during the morning hours on Saturday. GFS is mostly dry and colder
with 95% of the precipitation well south of the area.

With operational runs still divergent on the overall picture,
interrogated the most recent ensemble guidance and found that the
most recent gefs has trended further north. Nearly half of the low
pressure centers are favoring the north track with the other half
sticking to the operational solution to the south. 12z gefs 24 hr
probabilities for quantitative precipitation forecast > 0.1 inch have increased from 10-20% to 60-
70% from the 06z suite for Saturday morning. This is quite the
switch from the earlier solutions and will hopefully be the
beginning of a trend toward a better and higher confident agreement.

For the forecast, have leaned toward the wetter solution with the
potential for some mix in precipitation to start on Saturday. With
the further north track, temperatures should rebound fairly quickly
switching over any frozen precipitation to all liquid by late
morning. It should be noted that as the weekend nears, any increased
agreement toward a warmer solution may remove all chances for frozen
precipitation entirely.

Model solutions converge for Sunday and Monday as high pressure
builds in to the south, resulting in seasonable temperatures, dry
conditions, and partly to mostly cloudy skies.

Temperatures throughout the extended forecast are fairly seasonable
despite the active weather pattern. High temperatures on Thursday
will be above average with the following night also above average,
but overall, not seeing any warm or cold extremes.

&&

Aviation /06z Tuesday through Saturday/...
low clouds will be the story through the taf period. Through the
rest of the overnight hours, MVFR to possibly IFR ceilings are
expected to remain in place, along with patchy MVFR
visibilities. Drizzle will still be possible for a few hours at
some of the taf sites, which could briefly reduce visibilities a
little further.

During the morning hours, ceilings are expected to improve
somewhat, and some breaks to VFR are possible. Another chance of
rain (with little to no aviation impacts) will occur during the
afternoon hours, followed by another reduction in ceiling
height. MVFR ceilings are again expected to be prevailing by
evening, with some chance of IFR conditions at times.

Winds are expected to remain light (under 10 knots) through the
taf period.

Outlook...MVFR to possibly IFR ceilings are expected to continue
on Tuesday night and into Wednesday morning. MVFR conditions
are expected again on Thursday night and Friday, and possibly
again on Saturday.

&&

Iln watches/warnings/advisories...
Ohio...none.
Kentucky...none.
In...none.

&&

$$
Synopsis...Hickman/AR

National Weather Service Glossary of Abbreviations