Area Forecast Discussion
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FXUS61 KILN 172118
Area Forecast Discussion
National Weather Service Wilmington OH
418 PM EST Tue Jan 17 2017
A departing cold in the Ohio Valley combined with the passage of
an upper level low will permit a few sprinkles over the region
tonight. High pressure will build south of the region Wednesday
and provide a brief dry period. This high will move east early
Thursday, and the next chance of precipitation will occur with a
warm frontal passage early on Friday.
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
H5 low and trough axis coming through with a good PV anomaly with
deep enough low level moisture (1.5kft) to support an area of
light rain and/or drizzle. Do not expect to have precip in any
but my far southeast after 9Z given the h5 trough axis should be
the deterministic factor in the occurrence of precip, regardless
of how light or measurable it is.
Overnight lows will be cooler but generally mild for this time of
year, ranging from the mid 30s in the northwest to the lower 40s
in the southeast CWA.
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
The closed upper low will be situated over the OH/WV border at
12z and quickly exiting east. High pressure will build south of
the area through the day, coupled with a slightly lagging upper
level ridge. This ridge at both the surface and aloft will be over
the region tonight but will likely not be strong enough to scour
out the low level moisture trapped underneath a fairly strong
temperature inversion. Was initially concerned about the potential
for drizzle underneath this inversion but the depth of the
saturated air appears to limit this potential, coupled with the
absence of any strong upper level forcing due to a vort max or
jet. Generally kept it cloudy and did not let the min temperatures
drop much below the mid 30s given the expected cloud cover.
On Thursday, the upper level ridge crosses and flow turns easterly
at the surface. A warm frontal passage is slated to occur
overnight, along with an increasing threat for rain. Kept the rain
as stratiform and mentioned heavy potential where pops were likely
Models are slowing the progress of the warm front in the Ohio
Valley overnight Thursday. Believe that there may be enough
slantwise convection along the occlusion to promote thunder late
overnight, but did not include this in the forecast attm and kept
the ptype as stratiform versus convective in nature.
Temperatures will remain above normal. Forecast remains
relatively unchanged with a general minor bump in both highs and
.LONG TERM /FRIDAY THROUGH TUESDAY/...
The long range will open up with a closed low ejecting northeast
and taking on a negative tilt as it passes over the ILN forecast
area. A slug of PV will rotate across the area Friday morning
providing a strong source of lift. Omega values on the GFS also
light up at this time. PWAT values rise to near 1.10". GFS
forecast soundings do show the possibility of some thunder but for
now have left the mention out as thunder looks marginal. Given the
impressive lift, more than sufficient moisture, and instability
have kept PoPs categorical.
In the wake of Fridays closed low there will be a brief period of
subsidence on the backside of the PV, but the main question is how
quickly will the precipitation return. Overall ridging begins to
setup across eastern Canada and the northeastern United States
with an upper level trough over the western United States. The
pattern will be messy though as multiple waves of mid-level energy
can be found in the flow. The GFS is slightly further east with an
upper level low pushing north on the western side of the mid-level
ridge. As this occurs the ridge will slowly start to move east.
The GFS is slightly stronger with this low Saturday and tries to
bring in precip to the area Saturday afternoon across the western
zones. The CMC looks similar to the GFS while the ECMWF is
slightly weaker with the energy Saturday. Looking at forecast
soundings on the GFS for Saturday shows dry air between 850 and
700 mb which would favor a later onset of precipitation. Given the
above have trended the forecast towards the ECMWF solution and
kept Saturday drier.
Sunday, another stronger piece of energy will push east across the
southern United States and wrap up into an upper level low. As this
happens a wedge of PV will push northeast ahead of the low and move
across the ILN forecast area. PWATs at this time again rise to
around 1.00". Forecast soundings on the GFS show some dry air trying
to remain in various levels of the sounding at this time so have
kept PoPs at chance. Seeing how strong the upper level lift
currently looks on the ECMWF and GFS Sunday, PoPs will probably have
to be raised. Sunday into Monday the upper level low will drift
overhead keeping the clouds and a chance of rain in the forecast. It
should be noted that the low looks to be vertically stacked with dry
air entrained. This means that a break in the precip will probably
occur sometime on Monday (possibly in the morning) but given this is
day 7 have just broad brushed the PoPs at this time. On Tuesday the
upper level low will slowly drift east taking the rain and
precipitation with it.
.AVIATION /21Z TUESDAY THROUGH SUNDAY/...
Cdfnt is in the vicinity of I-71 at the start of the taf period.
Some clear spots around the front have allowed the cigs to jump to
VFR. However cigs are dropping back to MVFR behind the front. So
have a tempo group for the first hour of the tafs to take care of
Cigs will lower as the afternoon progresses and could reach IFR
at some spots after 00Z. Meanwhile, an approaching H5 vort will
increase the PVA aft 00Z and will give the chance of scattered
SHRA. Carried a VCSH at the tafs between 00Z and 12Z. Tafs get
into area of NVA tomorrow, so ended the VCSH around 12Z, but time
sections are showing that low level moisture will be trapped,
thus kept MVFR cigs.
OUTLOOK...MVFR/IFR ceilings possible into Thursday. MVFR/ IFR
ceilings are again possible Thursday night into Sunday.