Scientific Forecaster Discussion
fxus61 Kiln 181445
Area forecast discussion
National Weather Service Wilmington Ohio
945 am EST Mon Nov 18 2019
a large 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, with
greater chances for rain on Thursday, as low pressure moves
northeast into the Great Lakes.
Near term /until 6 PM this evening/...
mid level low over Indiana to pivot east-southeast across southern Ohio and
northern Kentucky through the afternoon. Breaks in the mid and
high level clouds will fill in with increasing cloud cover thru
the afternoon hours.
Can not rule out a sprinkle but forcing is weak so will continue
a dry forecast through the day light hours and just allow for
this increase in clouds.
High temperatures are expected to range from the mid 40s over
west central Ohio to 50 over south central Ohio and northeast
Short term /6 PM this evening through 6 PM Tuesday/...
broad longwave troughing will still be in place this evening and
into Tuesday, stretching across a large expanse of the eastern
Continental U.S.. the shortwave mentioned in the near term discussion will
be passing the area by this evening, leaving the middle Ohio
Valley in a brief weakness in the mid-level flow. As this
occurs, low-level moisture will be increasing significantly,
particularly at and below 850mb. Both the GFS/NAM suggest a
pocket of cold 925mb temperatures will be shifting east-southeast from
northern Indiana and into Ohio on Tuesday morning, steepening
low-level lapse rates, and likely producing thick cloud cover
below 3kft. Though forcing will initially be hard to come by,
any weak lift should be enough to produce drizzle out of this
sort of low-level thermodynamic profile. This does present some
concern with regards to surface temperatures, as some of the
northern / northwestern sections of the County Warning Area will be very close
to freezing at 12z Tuesday morning. While there is enough
confidence to put patchy fzdz in the forecast, the temperature
forecast is much lower confidence, especially with the thick
clouds moving in and disrupting the typical diurnal cycle. Given
this, and the fact that any precipitation should be generally
light, fzdz potential will be kept as just a mention in the
forecast -- without inclusion in the severe weather potential statement. As Tuesday progresses,
slightly stronger forcing will move into the region, as another
shortwave moves southeast from southern Wisconsin into Ohio.
This shortwave should be strong enough to allow for drizzle
/and/ light rain later on Tuesday, but it is notable that there
are still some placement disagreements between the various
models. Pops have been included County Warning Area-wide for Tuesday, but held
at 20 percent.
Temperatures on Tuesday look fairly similar to Monday, which is
unsurprising given the lack of any significant change to the
boundary layer forecast situation. As with Monday, the exact
temperature forecast is not quite high confidence, with
precipitation potential being the main concerning factor.
Long term /Tuesday night through Sunday/...
extended period begins with a 500 mb longwave trof extended down
across the eastern Great Lakes into the central Appalachians.
Some lingering light precipitation will be possible early
Tuesday night as embedded energy swings through the trof.
By 12z Wednesday the trof axis will have shifted to the East
Coast, with 500 mb ridging beginning to build into the Mississippi
Valley. This ridging will work eastward on Wednesday and will
provide a dry and near seasonal day on Wednesday.
Upper ridge axis shifts east across the region Wednesday night,
which should keep the area dry through at least through
sunrise. Surface low pressure will lift out of The Rockies
Wednesday night and into the western Great Lakes Thursday. 00z
models seem a little slower with the onset of the precipitation,
so trended that way. Gusty winds around 30 miles per hour are possible for
The surface low will lift into srn Canada Thursday night,
pulling a cold front into the region. Models differ in how
quickly the front works eastward on Friday and thus how quickly
drier air behind it advects in. The GFS is the quickest pushing
the front into Appalachians. The European model (ecmwf) is much slower, keeping
rain over the region the entire day. The 00z CMC, seems to lean
towards the GFS solution, which dries out the north, but keeps a
chance in Kentucky as the front hangs up there.
Differences in the models continue into the weekend. The 00z
ECMWF, lifts a surface low up across the region Saturday,
bringing widespread precipitation to the region. The thermal
profile on the European model (ecmwf) is warm enough for all rain. The GFS
meanwhile has a cold dry airmass over the region as high
pressure ridges in. The 00z CMC once again finds itself between
the two models. While the CMC brings a low along the front in
Kentucky, it lifts it thru eastern Kentucky, bringing pcpn
mainly to the southern half of the fa.
Ran a blend of solutions, but leaned towards the wetter
solution, thus went slightly warmer than guidance for Friday
night lows and tried to limit the amount of snow on the northern
edge of the pcpn shield Saturday morning.
Model solutions reconverge for Sunday as high pressure looks
like it will begin to build in.
Aviation /15z Monday through Friday/...
VFR conditions are expected through the first part of the taf
period, with increasing / lowering clouds the main story through
the day. Winds should be fairly light through the next 24
hours, with variable directions early this morning, becoming
generally out of the west during the day. High and mid clouds
are already in place over the region, but an increase in clouds
below 10kft is expected during the early to mid afternoon.
Confidence is high that clouds will drop below MVFR thresholds
after 00z, with some chance of IFR ceilings overnight into early
Tuesday morning. This appears most likely at kday.
Precipitation has been kept out of the forecast, but it does
appear that some drizzle (possibly requiring MVFR visibilities)
could be possible at the tail end of the taf period on Tuesday
Outlook...MVFR to possibly IFR ceilings are expected on
Tuesday. MVFR ceilings may continue into Tuesday night. MVFR
conditions are expected again on Thursday and Friday.