Scientific Forecaster Discussion
fxus61 Kiln 181750
Area forecast discussion
National Weather Service Wilmington Ohio
1250 PM EST Fri Jan 18 2019
weak high pressure will build across the region today offering
dry but cloudy conditions. A winter storm will track from
the lower Mississippi Valley through Kentucky Saturday and into
the upper Ohio Valley Saturday night. This storm will bring a
wide variety of precipitation types, including accumulating snow
and ice, on Saturday. The system will clear out late Saturday
night with much colder air and strong winds in its wake by
Sunday. Drier and bitter cold conditions will persist until
Tuesday, ahead of the arrival of the next precipitating system.
Near term /until 11 PM this evening/...
cloudy skies will persist with low stratus limiting any
significant rise in temperatures through the day, also
inhibiting any subsequent rapid decrease this evening. Generally
expecting near steady temperatures fluctuating 1 to 2 degrees in
Weak surface high pressure continues to build and promote dry
conditions today and this evening.
Short term /11 PM this evening through 6 PM Saturday/...
a significant winter storm will affect the region on Saturday.
Given expected temperature profiles at the surface and aloft,
snowfall amounts of 5-8" are likely along the I-70 corridor.
This threat extends further north and south, but amounts and
duration to the north, and warm air intrusion to the south are
keeping the forecast in a state of flux at this moment in time
and the watch continues to be the best product currently.
Flow backs with favorable isentropic lift developing across the
west between 06z and 09z tonight and into the east by 12z. Will
spread pcpn across the area by sunrise Saturday, at least west
of the I-75 corridor, and an extremely rapid expansion eastward.
Expect all snow north of I-70 with a mix central and mainly
rain over the Ohio River and southward. Any snow accumulation
through daybreak Saturday will be around a half inch and be
limited to west of I-75 and north of I-74 in Indiana. Warm
advection overnight will see steady or a slight rise in temps
tonight. Have lows from the mid/upper 20s north to the middle
Low level southerly jet of 50 kts offers good lift Saturday.
Rapid increase in pops to 100% from west to east Saturday
morning. With warm air advecting into the system ahead of the
low - expect pcpn to change to a mix south of the I-70
corridor/all rain south and all snow across the northwest.
Did not make sweeping changes to the snow totals but the favored
area where the warning was issued did see an increase given the
expectation of a heavy wet snow with rapid accumulations along a
narrow band. Rainfall of 1 to 1.5 inches may cause minor flood
issues in the far south.
Highs on Saturday are expected to range from near 30 northwest
to the lower 40s southeast and in Kentucky.
Will get more specific in totals with this afternoon's forecast
for the area south of the I-70 corridor. Regardless of the
amount of snow, a rapid drop in temperatures overnight will
necessitate an advisory for adverse conditions comprised of wind
chills and more importantly - the rapid freeze of any lingering
water on the roads. Generally - expect a 1 to 3 inch total
across the south. If the favorable deformation overachieves -
can not rule out the potential for some local 4 inch totals.
With Arctic air settling in expect Sunday morning lows from the
single digits northwest to near 20 southeast. Apparent
temperatures (wind chill) will be below zero north and west of
Dayton and in the single digits elsewhere by daybreak Sunday
with 15-20 mph winds gusting to 35 and 40 mph.
Long term /Saturday night through Thursday/...
forecast solutions have trended faster with this system and
faster with the cold air. 800 mb low track quickly into the upper
Ohio Valley early Saturday evening. Cold advection to result in
a change to snow from northwest to southeast. Winds will become
gusty with wind gusts of 35 to 40 mph expected. Coupled upper
level jets lead to a region of good upper divergence Saturday
into Saturday evening. Model signal points to favorable
deformation axis Saturday evening with strong frontogenetic
forcing. This may lead to some enhanced snow fall Saturday
evening prior to 06z when the best forcing shifts east.
Cold air will be rushing in Sunday on a north wind behind the
departing winter storm. Once lingering snow ends in far eastern
counties, strong subsidence and scant moisture associated with
1038 mb Arctic high pressure will likely keep precip from
occurring Sunday through Monday.
Next low pressure system is due to move in on Tuesday. Moisture and
temperatures will both increase rapidly on a southerly flow ahead of
the low, allowing mainly rain, with snow possibly mixing in. Colder
air filtering in behind the low will result in a larger proportion
of snow on Wednesday as the system works east of the region. Chance
of snow lingers Thursday as the low strengthens to the east, sending
a shield of precip back to the Ohio Valley.
Temperatures will be very cold Sunday and Monday, when highs are
forecast to reach the teens and 20s. Below zero temperatures and
wind chills are likely Sunday night. An abrupt warm up is expected
Tuesday with highs forecast to be close to 40. Another round of cold
advection is forecast to bring temperatures back down to the lower
30s by Thursday.
Aviation /18z Friday through Wednesday/...
MVFR cigs and occasional vsbys will prevail through the evening
hours as the area braces for a snow and mixed precipitation
storm affecting the tafs on Saturday, possibly all rain at
kcvg/kluk through late afternoon. Cigs will lift to the higher
end of the MVFR category in central Ohio (cmh/lck) tonight as
east winds kick in and provide some little bit of a drying
Kiln will be the challenge for this and any subsequent forecast
periods, spending the better part of the storm firmly in the
mix early on - snow, rain, and freezing rain before changing to all
snow beyond this valid forecast period of 18z.
Once precipitation overspreads the region from west to east
during the morning, cigs will lower to IFR if not LIFR in the
snow to the north, but remain on the magic cusp of 1000' where
the rain prevails earlier in the day in Metro Cincinnati and taf
Outlook...IFR conditions are likely with precipitation Saturday
afternoon and overnight, with MVFR/IFR conditions and gusty
winds through Sunday.
Ohio...Winter Storm Watch from late tonight through late Saturday
night for ohz026-034-035-060>063-070>072.
Winter Storm Warning from 4 am Saturday to 4 am EST Sunday for
Winter Storm Watch from late tonight through Sunday morning
In...Winter Storm Watch from late tonight through late Saturday
night for inz058-059-066.
Winter Storm Warning from 4 am Saturday to 4 am EST Sunday for