Area Forecast Discussion
Issued by NWS Wilmington, OH-- Highlight Changed Discussion --
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FXUS61 KILN 201046
Area Forecast Discussion
National Weather Service Wilmington OH
646 AM EDT FRI MAY 20 2016
A low pressure system will lift out the Tennessee Valley and into
the Upper Ohio Valley through tonight. This will bring widespread
showers to the region later this afternoon and overnight.
Scattered showers will linger into Saturday as the low pressure
system moves off to the east.
.NEAR TERM /THROUGH TONIGHT/...
Mid level short wave energy rotating around the base of the upper
level trough over the southern plains will eject northeastward
into the Ohio Valley region through this evening. As it does, a
developing surface low currently over the lower Mississippi Valley
will lift northeast into the upper Ohio Valley today into
tonight. An associated 30-40 knot 850 mb jet will pivot up across
eastern Kentucky through this afternoon, nosing into southern
portions of our FA by this evening. This will lead to shower
development across our south through early afternoon, becoming
more widespread and lifting up across our area this evening.
Instability is marginal at best, but is more impressive just to
our south. Think some of this may get advected up into our area so
will allow for a chance of thunder later this afternoon into this
evening across about the southeast third of our FA. Given the
track of the surface low, low level shear profiles will be very
impressive through this evening, but any severe threat should be
limited by the overall lack of instability.
PWs will push up around 1.5 inches late this afternoon/early
this evening across our south before gradually dropping off
through tonight. This could result in locally heavy rainfall,
especially with any embedded thunderstorms. One and 3 hour ffg is
running in the 1.5 to 2 inch range across our south and southeast
and the 2 to 2.5 inch range for 6 hour ffg. The 00z nam is the
most aggressive with the QPF, with a narrow axis of 2 to 2.5
inches nosing up into our northern Kentucky counties, and this
does have a little bit of support from some of the convective
allowing models like the nssl wrf. Meanwhile, the ECMWF, CMC and
GFS are more in the 1.5 to 2 inch storm total range into our
southern counties. With even the worst case scenario models just
getting us close to ffg and some uncertainty between the models
as to exactly where the heaviest axis will lineup, will hold off
on an FFA at this point, but include locally heavy rain in the
grids and a mention a flood potential in the HWO product.
Temperatures today will be a little tricky given the increasing
clouds and rain spreading into the south later this afternoon.
Will go ahead and range highs from the upper 60s southwest to
lower 70s in the northeast.
.SHORT TERM /SATURDAY THROUGH SUNDAY/...
The surface low will be located somewhere across southern Ohio
Saturday morning and is forecast to weaken as it drifts slowly off
to the east southeast through the day. This will result in
scattered lingering rain showers through the morning, before
beginning to taper off from the west through the afternoon as
some drier air tries to work in. Expect mainly dry conditions
Saturday night, but a mid level short wave will drop quickly down
across eastern Ohio on Sunday, resulting in the possibility of a
few showers across our east. Expect highs on Saturday mainly in
the upper 60s, warming into the lower 70s for Sunday.
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Sharp ridging over the Mississippi Valley region will move east
and envelop the Ohio Valley by Monday morning, providing a period
of dry weather and warming temperatures. Going into the new week,
the pattern appears more typical of late spring -- with warmer
southerly flow at the surface, and chances for precipitation as
occasional waves move along the generally-westerly mid-level flow.
Recent model runs have been slightly faster with the onset of the
pattern change, and now suggest that precipitation chances could
begin as early as Tuesday evening (in a regime of strong
southwesterly 925mb-850mb theta-e advection). Pseudo-zonal flow
beyond this time range will likely support occasional chances for
showers and storms during the rest of the week, but timing the
small-scale features out will be critical for specifics on this
part of the forecast as it gets closer to the current time.
Temperatures are expected to rise above normal through the long term
forecast period, especially beginning on Tuesday, when the southerly
near-surface flow becomes established. The occasional chances for
precipitation during the middle of the week will keep these forecast
numbers on the conservative side (upper 70s to around 80) for now,
but these could need to be increased slightly on any given day if a
brief dry / sunny period eventually becomes more certain to occur.
.AVIATION /10Z FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --All taf sites vfr this morning as widespread cirrus has moved into
the area ahead of the next system. There are some light returns
on the radar off to the southwest, but the atmosphere is
currently relatively dry though (PWATs around 0.6") so these
returns are likely evaporating before hitting the ground.
By later this afternoon the atmosphere will quickly saturate as
the upper level low approaches (PWATs on the GFS and NAM around
1.4"). The high res ARW, NMM, and RAP are in good agreement
bringing rain into CVG/LUK between 18 and 21 Z while the latest
run of the HRRR is about 3 hrs faster. Have followed the ARW,
NMM, and RAP solutions when constructing the TAFs. The latest run
of the NAM is now showing more instability than the previous run,
but looks to ambitious in destabilizing the atmosphere. The GFS
shows very little instability. Have kept the mention of thunder
out of the TAFs as the GFS appears the more likely solution.
For the most part this afternoon cigs will stay VFR until the
surface low arrives later this evening. As the surface low moves
overhead cigs will fall very quickly to IFR and then LIFR. GFS and
NAM forecast soundings are in very good agreement with this along
with SREF prob cig heights. Cigs will the likely stay down into
Saturday morning as TAF sites remain in close proximity to the
OUTLOOK...Thunderstorms possible Saturday.
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