ILN issues Area Forecast Discussion (AFD) at Nov 27, 10:13 AM EST893
FXUS61 KILN 271513
AFDILN
Area Forecast Discussion
National Weather Service Wilmington OH
1013 AM EST Wed Nov 27 2024
.SYNOPSIS...
A low pressure system will approach the region today, tracking
south of the area tonight into Thursday bringing a mix of rain
and snow to the region. After the passage of this system much
cooler air will work into the region for the weekend.
&&
.NEAR TERM /THROUGH TONIGHT/...
Update this morning was primarily centered on incorporating the
latest short term models into the overnight forecast and then
deriving snow/rain ptypes. Overall pops/wx had minimal changes,
timing was a little quicker on the back side of the precip,
which brought precip and hence, snow amounts down by a bit.
Tried to not make wholesale changes as this is an interim period
but the snow totals for the overnight period did not exhibit any
large decrease in a particular area. Most likely, snow amounts
seem to be overdone. However, this is indicative of
accumulation on grassy areas/cars/elevated surfaces and not
pavement/roadways which will be warmer to begin with.
Temperatures hovering in the lower 30s will also have snow
forecast/accum err towards a melting as they fall scenario.
Previous discussion:
Zonal flow mid level flow with surface high pressure sliding
east of the area early this morning. Isentropic lift across the
area will lead to thickening and lowering clouds this morning.
As clouds lower and the column moistens up rain will overspread
the area from the west this afternoon. The best coverage of rain
looks to occur west of I-71 thru the daylight hours with the
threat becoming likely toward evening. High temperatures to
range from the mid 40s northwest to near 50 southeast.
&&
.SHORT TERM /THURSDAY/...
Westerly mid level flow backs as a trof develops to our west
and tracks thru the Great Lakes overnight into Thursday. In
response to this upper support a progressive surface low to
track from the Lower MS Valley this evening to the position over
WV by morning. Widespread precipitation will overspread the
region thru the evening. Initially the column is sufficiently
warm enough that all pcpn falls as rain. As the boundary layer
cools expect pcpn to mix with and change over to snow over the
northwest during the late evening and then work southeast
overnight. The best threat for measurable snow is over East
Central Indiana and West Central Ohio. Latest HREF shows a
60-70 percent chance for 1 inch or more of snow from Richmond,
Indiana to the Bellefontaine. This has trended up from the 12Z
runs and shifted a little south where the best band of snow
looks to exist. Allowing for cooling in this band have blended
in the cooler 3KM NAM hourly surface temperatures. This yields
a storm total thru early Thursday around an inch in spots along
this corridor. With temperatures being marginal - a slight
shifts will yield changes to snow amounts.
Metro model shows road temperatures in the upper 30s - so
impacts look to be limited to reduced visibilities and slick
spots on bridges and overpasses. Most of accumulation looks to
be on grassy areas. Will continue to highlight the potential
for minor travel impacts.
Precipitation ends from the west to east Thursday morning as
the low shifts off to the east. Clouds look to linger thru most
of the day with some improvement late. Lows tonight range from
the lower 30s northwest to the upper 30s southeast. Highs Thursday
range from near 40 northwest to the mid 40s southeast.
&&
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
In the wake of departing low pressure, longwave troughing will
be deepening across the eastern United States as ridging builds up
the West Coast. This will bring about winter-like temperatures in
the Ohio Valley. In the northwest flow diving into the trough, minor
disturbances will ripple through the region, offering occasional
periods of light snow.
The first of these disturbances appears to be weak and moisture-
starved, so only low chances of light snow are expected across west-
central through central Ohio. The second disturbance will be
taking a more southerly approach, so light snow is possible south of
Interstate 70 Saturday night. Will need to monitor this system for
potential minor impacts due to light accumulations in the very cold
air mass (temperatures in the 20s dropping into the teens late).
Well below temperatures will be maintained through the rest of the
extended period as mid-level northwest flow continues.
&&
.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
Isentropic lift will lead to thickening high and mid level
clouds this morning as high pressure shifts to the east.
Surface low pressure will track into the Lower MS Valley this
evening and south of the area overnight. Moisture will increase
ahead of this system with VFR ceilings lowering thru the
daylight hours. Rain begins to move into the area this evening,
overspreading the TAF/s from west to east. Ceilings will lower
to MVFR with IFR conditions overnight. Snow may mix with rain
toward sunrise mainly across KDAY and KILN prior to ending
early Thursday. Precipitation ends early Thursday as the low
shifts east of the area and Ceilings will rise into the MVFR
category after sunrise.
OUTLOOK... MVFR/IFR CIGs/VSBYs possible Thursday morning. MVFR
CIGs possible again Thursday night into Friday.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...None.
KY...None.
IN...None.
&&
$$
SYNOPSIS...AR
NEAR TERM...Franks/AR
SHORT TERM...AR
LONG TERM...
AVIATION...AR
Source:
ILN issues Area Forecast Discussion (AFD) at Nov 27, 10:13 AM EST---------------
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