Scientific Forecaster Discussion
fxus61 Kiln 200217
Area forecast discussion
National Weather Service Wilmington Ohio
1017 PM EDT Thu Sep 19 2019
high pressure over New England will slowly migrate south
towards the mid Atlantic and the Carolinas through Friday.
Surface flow around this high will turn southerly, bringing an
increase in moisture. The high will then remained anchored
across the Carolinas this weekend as a slow-moving cold front
approaches the Ohio Valley Sunday night, and crosses early
Near term /until 6 am Friday morning/...
still some few-sct higher SC/lower ac around this evening.
Southwesterly low level flow will continue across our area
through the night as surface high pressure remains centered off
to our southeast. The low level jet is forecast to gradually
increase through the night and this will likely help some
clouds persist through much of the overnight. Some developing
low level convergence may even lead to a few showers as noted
by some of the higher res cams. But with the airmass relatively
dry, will maintain a dry forecast at the moment. Lows tonight
will be in the low to mid 60s.
Short term /6 am Friday morning through Friday night/...
some more cloud cover will keep tomorrow slightly cooler than
today and the slight chance of showers will have ended early in
the evening/late afternoon in favor of clearing skies overnight.
Highs will be again in the mid 80s, with lows in the lower 60s.
Long term /Saturday through Thursday/...
overall thinking throughout the long term period remains the
same as previous discussions. Extended warm temperatures
continue Saturday and Sunday with a chance for rain late Sunday
night into Monday. Beyond the cold front passage on Monday,
uncertainty increases as to whether or not the region remains
stuck in a abnormally warm pattern or if a return to normal is
By Saturday morning, an anomalous subtropical ridge will extend
from the Gulf Coast to eastern Canada as a shortwave trough
lifts northeastward into the northern Great Plains. The trough
progresses eastward over the weekend leading to height falls
over the Great Lakes as the trough becomes less amplified.
Accompanying the trough, a rather weak surface cold front
extends southwestward from a parent low in Canada. With the
minor delay in frontal arrival from previous forecasts, Sunday
is becoming increasingly concerning regarding very warm
temperatures and low dewpoints leading to developing fire
weather dangers, especially Sunday afternoon. As the front
approaches from the west, a tightening pressure gradient may
result in elevated wind speeds and potentially high wind gusts
Despite the rather dry airmass, ahead of the front arrival on
Monday, a narrow band of anomalously high precipitable water
originating from the southern US associated with the parent low
in Canada should lead to chances for precipitation. The main
question is whether or not the forcing along the front can take
advantage of the relatively small window of abundant atmospheric
moisture. Most guidance suggests this particular feature will
not produce enough precipitation to put any dents into the dry
period that started several weeks ago. Newest 12z eps members
persist with the situation described in previous discussions.
Few members show widespread rainfall accumulation between
0.25-0.50 inches across the area. There very well could be a few
areas that miss out on rain completely. After the frontal
passage on Monday, drier air moves in from the northwest,
essentially ending chances for rain during the day on Monday. On
Tuesday, afternoon temperatures may be near normal, allowing
for a break from the 10-15+ degrees above normal temperatures
that we have been experiencing.
On Wednesday and Thursday, uncertainty remains in the forecast.
Model guidance suggests zonal flow may develop over the Ohio
Valley as the trough associated with the cold front moves
eastward. Zonal flow may be replaced by an amplifying
subtropical ridge later next week. However, the amplitude and
location of the ridge axis is still uncertain at this time. The
current forecast is for slightly above normal temperatures and
minimal chances for rain for the middle of next week.
Aviation /02z Friday through Tuesday/...
scattered cu and even a few tcu are evident on visible
satellite imagery across our southwest. Expect these clouds to
gradually dissipate as we lose the diurnal heating. However,
with some lingering moisture, will hang on to a few higher
SC/lower ac through the night. We will remain in weak southwest
flow through the day on Friday. With a relatively dry airmass
in place, will just allow for some scattered cu through the
later part of the taf period.
Outlook...thunderstorms possible on Sunday night into Monday.