ILN issues Area Forecast Discussion (AFD) at Nov 20, 6:36 PM EST643
FXUS61 KILN 202336
AFDILN
Area Forecast Discussion
National Weather Service Wilmington OH
636 PM EST Wed Nov 20 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 THURSDAY/...
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 /THURSDAY NIGHT/...
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 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 /00Z THURSDAY THROUGH MONDAY/...
VFR conditions will start the TAF period, with busier weather
coming over the next 24-36 hours.
Winds: Winds will be generally light through the next few hours,
before westerly winds increase after 06Z, with gusts to around
20kts. These winds will further increase by Thursday mid-day and
afternoon, with gusts to around 25kts. Winds will decrease
Thursday evening and shift from west to southwest.
Precipitation and Ceilings: A few light rain showers are
possible in the next few hours, with no impacts expected. Snow
showers are then expected Thursday 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 day.
Finally, during the evening, a steadier area of snow will move
into the area (for all TAF sites except KCMH/KLCK). This will
bring IFR visibilities, likely IFR ceilings, and some
accumulations.
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
SHORT TERM...CA
LONG TERM...
AVIATION...Hatzos
Source:
ILN issues Area Forecast Discussion (AFD) at Nov 20, 6:36 PM EST---------------
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