Scientific Forecaster Discussion
fxus61 Kiln 261851
Area forecast discussion
National Weather Service Wilmington Ohio
251 PM EDT sun Mar 26 2017
showers and thunderstorms will develop today into tonight as low
pressure moves to Lake Michigan. After a brief visit by high
pressure and drier air early Monday, another low will bring more
showers and thunderstorms Monday night and Tuesday. Dry weather can
be expected Wednesday under high pressure.
Near term /through tonight/...
upper level low pressure is currently in central Illinois with
the second band of precipitation getting ready to exit the County Warning Area.
A third band of precipitation has now formed across the ind
forecast area and is expected to push east through central Ohio
later this afternoon into early evening. The latest run of the
GFS is showing slightly higher mu cape values for this afternoon
(some values slightly above 1000 j/kg). For the most part
forecast soundings show this cape to be weak and skinny.
Shortwave cooling and 800 - 500mb winds of 35 to 40kts will make
damaging winds and severe hail the primary severe threats for
this afternoon. Due to the above Storm Prediction Center has the area in a marginal
Short term /Monday through Monday night/...
Monday an area of upper level low pressure will push east across
the central United States. This second system will be right on
the heals of the Sunday upper level low and will bring a quick
return for the chance of showers and thunderstorms. After the
brief break Monday morning the upper level low will move towards
Illinois with pockets of positive vorticity advection crossing the iln forecast area.
Pwats will also be on the rise towards 1.10" (nam and gfs). The
best upper level lift from the rrq will be further south towards
Kentucky but with a weak upper level jet streak moving overhead
think upper level support will be more than sufficient. Mu cape
values on the NAM across the southern zones are nearing 1500
j/kg while are only around 500 j/kg on the GFS. On the GFS the
greatest 0-3km bulk shear is also further south across Kentucky. The
NAM on the other hand is more north with the greatest shear and
instability. Thanks to the mentioned above Storm Prediction Center has most of the
area in a marginal risk.
Long term /Tuesday through Sunday/...
weakening upper level shortwave and associated surface low to track
through the Ohio Valley Monday night. This feature will provide
widespread showers and thunderstorms. As this progressive system
shifts east pcpn will come to an end Tuesday. Temperatures will
remain above normal, with tuesday's highs ranging from near 60
northwest to the upper 60s southeast.
Surface high pressure to build across the Great Lakes at mid week.
This will provide dry weather Wednesday into Thursday. Temperatures
will be closer to normal, with highs on Wednesday ranging from the
mid 50s northwest to the mid 60s southeast.
Model solutions diverge on handling late week weather system. GFS
continues to be outlier and takes the Southern Plains upper low into
the Ohio Valley and therefore is quicker with return pcpn.
The more consistent European model (ecmwf) and Canadian solutions have the closed low
lifting northeast into the upper MS valley Friday. Will continue to
trend the forecast toward the ECMWF/Canadian.
Will bring chance pops into the west Thursday and increase these
pops to likely Thursday night into Friday, as moisture and
instability increase across the region. Will mention chance pops for
thunder Friday afternoon into Friday evening. Temperatures to
continue a little above normal with highs from the mid/upper 50s
north to lower/mid 60s south for Thursday and Friday.
As this system exits the region pcpn will end Saturday. High
pressure to offer dry weather through the remainder of next
Aviation /19z Sunday through Friday/...
low pressure system is currently rotating over central Illinois
and slowly pushing northeast. Second band of precipitation is
currently moving through iln/ day with restrictions down to IFR
visibilities/ MVFR ceilings possible. As this second round of
precipitation passes the taf sites ceilings and visibilities
will recover to VFR. A third band of showers has formed in
central Indiana this afternoon and is forecasted to push east
through the taf sites later this afternoon into evening hours.
As this band pushes east forecast soundings continue to show the
area destabilizing. As this occurs the amount of lightning
strikes will also increase. Due to this have added a tempo
group for thunder into all the taf sites. Went ahead and used
current radar trends to help with timing of tempo groups. As the
line passes through the taf sites some gusty winds and
restrictions in visbilities and ceilings will be possible.
As the line passes the taf sites a brief recovery to VFR will
occur with a return of MVFR ceilings possible Monday morning.
The NAM is the most aggressive with the return of the MVFR
Monday morning while the GFS is more optimistic. The sref
probabilities are more in between the two and have decided to
trend tafs this direction.
During the day Monday any MVFR ceilings will quickly recover to
VFR with another upper level low moving east across the central
United States. By middle of Monday afternoon positive vorticity advection and upper level
divergence will be overhead meaning a return of showers and
thunderstorms. For now have left mention out of tafs as this
remains near the end of the period, but future taf packages will
likely have to incorporate this.
Outlook...MVFR ceilings and visibilities will be possible late
Monday into Tuesday morning.