ILN issues Area Forecast Discussion (AFD) at Nov 21, 1:15 AM EST543
FXUS61 KILN 210615
AFDILN
Area Forecast Discussion
National Weather Service Wilmington OH
115 AM EST Thu Nov 21 2024
.SYNOPSIS...
Multiple disturbances will progress through the region as we
head toward the end of the work week bringing much cooler
temperatures, gusty winds, and periods of rain and snow showers.
Dry conditions return to the region for the weekend before
precipitation chances return on Monday. Weekend temperatures
return to seasonable normals.
&&
.NEAR TERM /THROUGH TODAY/...
The main cold front has moved well east of the area, but
observations are indicating a secondary front (or trough axis)
is crossing east into the area. The main impact from this
secondary front is a wind shift from SW to W, along with gusts
in the 20-30 knot range. KDAY recorded a peak wind of 29kts at
0147Z. Gusts will subside slightly behind the front, but the
region will eventually settle into a breezy scenario through the
rest of the overnight hours -- with occasional gusts to around
20kts on westerly flow.
No significant changes to the overall thinking for the snow
showers and banded snow in the morning. 00Z runs have
highlighted the greatest accumulation potential with these bands
more in the west-central Ohio to central Ohio corridor, likely
as there is a greater chance for repeated bands of snow. Further
south, such as in the Cincinnati area, the heavier snow showers
may only impact the area for a couple hours. Regardless,
accumulation potential for this initial shot of snow showers
still looks to be rather limited for roadways, with impacts
from the briefly reduced visibilities as perhaps a greater
factor -- and perhaps some accumulations on roads if repeated or
heavier snow showers occur at a given point.
Previous discussion!! >
Continued complicated forecast in store for the next couple of
days. Synoptically, the 500H closed low located over Minnesota
has begun the process of wrapping a speed max around its base.
This will be the forcing needed to rapidly strengthen and
intensify a developing surface low located across the eastern
Great Lakes and into Appalachia. The isallobaric response will
greatly increase our pressure gradient and enhance the thermal
response with another push of strong CAA.
So, sensible weather wise... Given the tight pressure gradient
in place, wind speeds will remain somewhat elevated during the
overnight hours, sustained around 10-15 MPH with some gusts
possible. Additionally, the enhanced CAA moving into the region
will plummet our temperatures and we'll quickly fall into the
30s overnight. However, with the wind, it will feel like we're
in the 20s (remember, even though NWS has changed its cold
weather products (visit:
https:/www.weather.gov/images/iln/2024WinterColdCriteria.png
for more information) wind chill is not going away!!).
As the upper level low progresses toward the Ohio Valley, a vort
max wrapping around the western side and base of the low will
promote ascent coupled with steep low level lapse rates within
the DGZ. This, combined with a fairly saturated column, will
result in banded snow showers moving through the region during
the early morning hours on Thursday. This initial round of
precipitation will be limited in coverage but has the potential
to result in heavier bursts of rapidly accumulating snow coupled
with quick reductions in visibility. AM rush hour pavement
temperatures are forecast to be well above freezing, however, it
is not unheard of for a quick burst of heavy snow to overcome
warm-ish pavement temps (think <38F). Otherwise, any
accumulations will be limited to grassy areas of elevated
surfaces.
&&
.SHORT TERM /TONIGHT THROUGH 6 PM FRIDAY/...
The above mentioned banded snow will continue during the early
morning hours through 10AM-ish before moving off to the
southeast. We will have a lull in afternoon precipitation before
an additional round of snow arrives during the evening hours
(more on this later).
Strong west/northwesterly flow continues through the day on
Thursday and sustained winds around 15-20 MPH with gusts up to
30MPH will dominate the afternoon hours. This continued CAA
keeps cold temperatures in the region and Thursday high
temperatures likely won't even break 40F for most areas. These
temps combined with gusty winds will once again produce wind
chills in the 20s. Strongest winds will decrease again shortly
after sunset.
As the parent low pressure system continues to spin, it wraps
yet another (somewhat stronger) vort lobe around its base and
this will be the forcing for our second shot of snowfall
associated with this system. This snowfall will be less banded
and more widespread in nature where ascent takes place. Recent
hi-res runs suggest a slight westward shift and therefore, have
trended higher PoPs over the Tri-State and OH/IN border and
lowered PoPs near central OH/ eastern KY. Once again, pavement
temperatures should be warm enough to preclude notable impacts
but some accumulation on grassy/elevated areas or overpasses is
possible. Snowfall moves southeast out of the region shortly
after midnight and overnight temperatures fall to the low
30s/upper 20s.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
While the upper low will be east of the area at the start of the
period, one more impulse rotating around that system will drop south
across the region on Friday. This combined with low level warm
advection will result in more showers Friday into Friday evening.
This could start out as a mix of rain and snow showers before
changing over to all rain as low level temperatures rise.
Temperatures will still be below normal on Friday, although not as
much as the previous day. Then there will be little drop in readings
for Friday night.
Heading into the weekend, mid level heights will rise as the flow
becomes zonal. Surface high pressure will pass south of the region.
Temperatures will continue to moderate and even get above normal by
Sunday.
Short wave over the upper Mississippi Valley on Monday will progress
east across the Great Lakes on Tuesday. This will result in low
pressure and a cold front passing through the area late Monday into
Monday evening. Showers are forecast to occur out ahead of this
system. High pressure will build in behind the front bringing dry,
but cooler conditions into midweek.
&&
.AVIATION /06Z THURSDAY THROUGH MONDAY/...
Deep mid level low centered over Lower Michigan to track across
northern Ohio today and into PA tonight. Disturbance to rotate
around this low thru the area this morning. As a result snow
showers are expected this morning, with the possibility of some
banded heavier areas of snow. These snow showers will be hit or
miss, but areas under heavier snow showers or bands could have
temporary IFR visibilities and lower end MVFR ceilings. Some
lighter snow showers may continue into the early afternoon.,
A second mid level disturbance and associated surface low to
rotate around the 5H low thru Indiana/southwest Ohio this
evening and into KY overnight. In response to this feature,
a steadier area of snow will move into the area (for all TAF
sites except KCMH/KLCK). This will bring IFR visibilities,
and MVFR to IFR ceilings, and some light snow accumulations.
The snow will taper off overnight with MVFR ceilings continuing
until Friday morning.
West winds around 10-12KTS will gust to around 20kts at times
overnight into Thursday morning. These winds will increase by
Thursday midday and afternoon, with gusts to around 25kts.
Winds will then decrease this evening and shift from west to
southwest.
OUTLOOK...Reduced visibilities with snow may continue into
Friday morning. MVFR ceilings will likely continue through
Friday and into Saturday. Gusty winds are possible on Friday.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...None.
KY...None.
IN...None.
&&
$$
SYNOPSIS...CA
NEAR TERM...CA/Hatzos
SHORT TERM...CA
LONG TERM...
AVIATION...AR
Source:
ILN issues Area Forecast Discussion (AFD) at Nov 21, 1:15 AM EST---------------
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