Area Forecast Discussion
Issued by NWS Wilmington, OH
FXUS61 KILN 291929
Area Forecast Discussion
National Weather Service Wilmington OH
329 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 AM FRIDAY MORNING/...
Upper level low was analyzed over southwest Ohio today via
the 29.12z 250 mb map. Embedded in the upper low are pockets of
PV that are rotating around. This afternoon coverage will
continue to drift north and west around the low. The next wedge
of PV is forecasted to rotate around the low and move overhead
between 2 and 6z. At this time an inverted trough axis currently
over West Virgina will also push west with a weak surface low
pressure forming over the area. Omega values on the RAP, GFS, and
NAM also all highlight lift during this time frame. PWATs at this
time are forecasted to be around 1.1" with lower PWAT air being
shunted west. High res models have come into pretty good agreement
with timing so have increased PoPs during this time frame. Given
the strong upper level lift moving overhead and a possibility for
some higher rainfall totals will go ahead and highlight the chance
for isolated heavy rain in the HWO.
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
During the day Friday the upper level jet at 250 mb will
strengthen over the eastern zones with the main low level
convergence occurring over the northern part of the CWA. As the
low rotates north Friday lower PWAT air that has wrapped around
the low (0.75") will pull over the CWA with greater than 1.00"
PWATs confined to the southwest and northern parts of the CWA.
Have further refined PoPs to have the highest chances towards the
north with slightly lower values across the central parts of the
CWA. There also is instability present in both the GFS and NAM
forecast soundings (between 500 and 1000 J/kg of ML CAPE) Friday
afternoon which means thunder will be a possibility. Any slight
wobble in the upper low can easily change the eventual location of
higher precipitation totals.
On Saturday the upper level low will head north towards the
Indiana/ Michigan border with low level convergence and PVA
increasing over the area. PWATs for Saturday aren`t impressive
with values only around 1.00". Have gone ahead and increased PoPs
for Saturday to account for the upper level lift mentioned above.
.LONG TERM /SUNDAY THROUGH THURSDAY/...
The general consensus of the models is to start to lift the upper
low off to the northeast through the day on Sunday. This should
allow for a deceasing chance of pcpn by the start of the long term
period and will just linger some slight chance pops across the area
through Sunday afternoon. Highs on Sunday will generally be in the
The 12Z ECMWF and the 12Z CMC are now maintaining a closed upper low
through a good part of next week as it shifts off to the east, with
the 12Z CMC slower pushing it east and even retrograding it some
back across Pennsylvania through mid week. Meanwhile, the 12Z GFS
continues it trend to weaken the upper low as it moves northeast
while building some ridging across our area through the rest of the
long term period. Likely as a result, there is also quite a bit of
variability on the track of Matthew with it possibly riding up off
the east coast through mid week. This all spells out some
uncertainty in our sensible weather as we progress through the
upcoming week. At this point will discount the CMC and lean toward
more of a blend of the ECMWF and GFS, which would keep us mainly dry
through mid week along with a gradual warming trend each day. The
ECMWF is faster than the GFS with a possible front moving in through
late week. Will again go with a blend and allow for some lower
chance pops to work in from the west through the day on Thursday.
.AVIATION /19Z 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.