Scientific Forecaster Discussion
fxus61 Kiln 211923
Area forecast discussion
National Weather Service Wilmington Ohio
323 PM EDT Sat Oct 21 2017
high pressure will shift off to the east through the day on
Sunday, providing for one last day of dry conditions and above
normal conditions. An upper level disturbance and an associated
cold front will bring an increasing chance of showers Sunday
night into Monday. This will also usher in a cooler airmass
for next week.
Near term /until 6 am Sunday morning/...
a fair amount of mid and high level cloudiness has overspread
the area this afternoon and this is helping to keep
temperatures down a bit. In a continued southwesterly flow
pattern, expect to see some mid and high level clouds persist
through the night, leading to partly cloudy conditions. This
combined with the possibility of winds staying up a tad, should
result in lows mainly in the 50s overnight.
Short term /6 am Sunday morning through Sunday night/...
the mid level trough axis will shift east out of the
Mississippi Valley and into the lower Ohio Valley Sunday into
Sunday night. As it does, short wave energy rotating through the
base of the trough will lead to a developing surface wave/low
that will approach our area late Sunday night. The 12z models
have trended a little faster with this so have sped up pcpn
onset a few hours for Sunday night, especially across our
Highs on Sunday will be somewhat dependent on cloud cover, but
in continued southerly flow, highs should still push well into
the 70s. Lows Sunday night will be in the upper 50s to lower
Long term /Monday through Saturday/...
the long term will open up with a pattern change taking place as a
surface low approaches the County Warning Area from the southwest. The pattern will
be rather complex with a potent upper level low ejecting northeast
over Kentucky as it takes on a negative tilt. At the same time an
upper level trough axis will be located over the central United
States. During the day Monday the upper level low will move overhead
along with a wedge of positive vorticity advection. Pwats with the low are expected to surge
to around 1.50" across the area or near record values for this time
of year. Even though instability is lacking Monday it should be
noted that low level shear values are extremely impressive. Surface to 1
km bulk shear is nearing 45 kts across the southeast. We will
continue to watch this to see if any instability can work its way
north. The other concern with this system will be the potential for
heavy rain. For now, most model totals remain in the one to two inch
range (esp. Across the south and east). Confidence on rainfall
totals still remains low though as most gefs members indicate around
Monday night into Tuesday the surface low will exit east with a weak
cold front pushing through. The main upper level through axis that
was to our northwest Monday afternoon will begin to deepen and head
southeast towards the iln forecast area Tuesday morning. As this
occurs 850 mb temperatures will start to drop with highs not even
expected to reach 60 degrees Tuesday. In fact, Monday looks like the
warmest day of the extended. During the day Tuesday the upper level
low will then move overhead. As the core of the upper level system
moves overhead 850 mb temperatures will slowly drop below 0 degrees
c across the western zones. Due to the upper level low and
steepening low level lapse rates have kept the chance of
precipitation in Tuesday.
Wednesday the upper level low will take its time to exit the area
allowing the chance of showers to continue across our eastern zones.
By Thursday morning the upper level low will be exiting east with
the best ageostrophic convergence overhead. As this happens weak
surface high pressure will temporarily move overhead with winds
going calm. Temporary clearing is also scheduled to take place which
will make temperatures in the mid 30s possible Thursday morning
(maybe a freeze even if things line up right).
Thursday the upper level low will eject east with mid level heights
temporarily rising in the afternoon. 850 mb temperatures also
briefly rise to around 8 degrees c, but looking at the gefs and eps
thinking is that high temperatures will probably be in the upper 50s
to around 60 degrees Thursday. Friday though Sunday another upper
level low will deepen across Midwest Canada as heights rise off the
Pacific northwest coast. 850 mb temperatures behind this system fall
to around 7 degrees c below zero. Timing remains highly variable
here though so have only trended temperatures down at this time.
Aviation /20z Saturday through Thursday/...
upper level ridging will continue to shift off to the east
through the taf period. This will allow for some mid and high
level clouds to continue to overspread the region. Southerly
flow will also gradually increase as we get on the back side of
the high. This may help keep winds up a bit tonight so will not
hit kluk quite as hard with fog overnight. Otherwise, VFR
conditions are expected through the period.
Outlook...MVFR ceilings and visibilities possible Sunday night