Area Forecast Discussion
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FXUS61 KILN 291748
Area Forecast Discussion
National Weather Service Wilmington OH
148 PM EDT Thu Sep 29 2016
A large area of low pressure will remain in place over the Ohio
Valley through the rest of the week, providing cool and occasionally
rainy conditions. Chances for rain will begin to diminish on
Saturday, as the low gradually begins to move to the northeast.
Drier and warmer conditions are expected for Sunday and Monday, with
surface high pressure building in from the west.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
1245 PM Update > Refined forecast a little while ago with a
healthy blend of previous forecast and HRRR ensemble data which
has a good handle on batch of rain/few storms along/west of the
Scioto Valley. This should continue to peel slowly northwest into
central/southwest Ohio as it continues to slowly weaken/erode on
the nrn edge as it gets removed further from stronger flows and
forcing. Other showers/storms developing along old occluded front
in ern OH and these have a trajectory NW back toward cntl OH for
mid/late afternoon. As we approach peak heating over the next
couple of hours...other showers/storms will form in isold/sct
fashion across nrn KY/swrn OH. Still looks like primary threat for
stronger updrafts is east of the ILN area - though a stronger cell
could wander into the Scioto Valley between 3PM and 5PM. Also
increased rain chances this eve along/south of Ohio River...recent
HRRR runs and new 29.12Z NSSL WRF have been showing this area
lighting up in a narrow band of rain/storms as stronger shortwave
dynamics rotate NW across nrn KY this evening. Another large
band/arc of showers and storms will likely develop later this
evening into the overnight across the area but timing of this is
not good among the hi-res guidance. Most concern for impact
through tonight will be localized flooding with narrow bands of
moderate/heavy arcs of rain rotating around the upper low.
.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/...
Overnight, a swath of showers (associated with the upper forcing
and whatever is leftover from afternoon convection) is forecast to
move westward through the ILN CWA. If nothing else, this forecast
for rain makes the potential for fog tomorrow morning a little
more uncertain, even if conditions would otherwise be favorable.
Patchy fog wording will be included in the forecast, along with
50-70 percent chances of precipitation.
As the mid-level low starts to swing northward again on Friday,
there is reasonable model agreement in a relatively dry wedge
entering the south-central section of the ILN CWA during the
afternoon, with little in the way of forcing. PoPs on Friday
afternoon and evening will range from 20-50 percent, with the
highest values in the northern and northeastern sections of the
forecast area. With systems like this, and still plenty of room
for error in timing out the vorticity maxima rotating around, this
PoP forecast should still not be seen as an explicit forecast of
specific timing and placement.
Precipitation chances will begin a more significant decrease on
Saturday, as the low starts a quicker motion out of the Ohio
Valley and back into the Great Lakes from whence it originated.
Early on Saturday, the western half of the ILN CWA will be most
likely to receive additional precipitation, but a gradual drying
from south to north is expected by afternoon.
The relatively small diurnal temperature ranges will begin to
expand a little by Friday, and especially by Saturday, as slightly
drier overall conditions allow for a little more heating in the
afternoons. In fact, the forecasted highs on Saturday (upper 60s
to lower 70s) are only a little bit off from normals for early
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
This period will be characterized by a much warmer drier/period
vs the short term. On Sunday morning...the closed low will be
drifting northeast...weakening...and opening up into a more
progressive shortwave trough over New England by Monday.
Thus...there is still a small threat of showers into Sunday but
right now the timing/placement of this threat is very tough but
seems focused north of I-70 closer to mid level cold pool. Large
scale ridging ahead of the next longwave trough over the west will
allow for dry weather Monday thru Wed as high pressure at the
surface moves across the eastern U.S. Temperatures will be warming
steadily and by the middle of next week should be well into 70s if
not the lower 80s with dewpoints hanging tough in the 50s.
.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
Low confidence TAF forecasts this cycles due to variable cigs
amidst moist/unsettled pattern under upper low. Bands of
rain/embedded storms should affect all sites from time to time but
timing/placement of rain bands is problematic at best. Bottom
line...a good deal of shower mention are in the TAFS...either in
VCSH fashion or predominant weather. Thunder is highlighted
through this afternoon in the Columbus area terminals closer to
old/weak occluded boundary and nearest best moisture transport
this afternoon/evening. Trended vsbys from VFR down to MVFR in
the overnight and with associated showers. Cigs are all over the
place...though generally lifting to VFR this afternoon but
occasionally down to MVFR in showers or in tempo groups. With the
onset of stronger moisture push and rain this afternoon and night
across the TAF sites...am bringing vsbys and cigs down well into
MVFR and even IFR late in the night given weak/convergent flows in
the boundary layer near weak low pressure to the south.
OUTLOOK...MVFR ceilings and visibilities possible with showers
Friday afternoon through Saturday.