ILN issues Area Forecast Discussion (AFD) at Nov 29, 9:19 PM EST598
FXUS61 KILN 300219
AFDILN
Area Forecast Discussion
National Weather Service Wilmington OH
919 PM EST Fri Nov 29 2024
.SYNOPSIS...
Snow showers and flurries are expected tonight in a brisk
westerly flow. A disturbance is forecast to bring light snow
accumulations Saturday night into Sunday. Drier weather arrives
later on Sunday after the disturbance moves east.
&&
.NEAR TERM /THROUGH SATURDAY/...
Flurries/ moderate snow showers have continued to push through
the region this evening, allowing for a light dusting on
roadways/sidewalks/elevated surfaces. Given that this is weakly
forced precip in cyclonic flow, there isn't much guidance to
help with end time, however, looking at the HRRR/RAP and NAM
850mb RH... the highest moisture content looks to move east out
of the ILN CWA by midnight tonight or shortly after, so have
tapered off snow showers around that time.
Winds remain elevated overnight, around 10-15 MPH with some 20
MPH gusts. Currently, temps across the region are in the low 20s
and feels like temps are in the single digits. Clouds clear out
as that moisture moves east and we should end up with mostly
clear skies after midnight. Therefore, have tweaked overnight
lows a tad lower and dropped them comfortably into the teens
area wide as radiational cooling processes will take over.
Previous discussion--> Weak boundaries and disturbances
embedded in a cyclonic westerly flow are triggering snow showers
and flurries from a relatively shallow layer of moisture and
instability. Main area of concern is roughly from I-70 south to
the Ohio River. This loosely organized band of snow showers is
best represented on the HRRR which shows minor accumulations
late this afternoon through this evening. Went well above NBM
pops for this short duration event. Main impact appears to be
brief reductions to visibility with winds gusting over 20 knots
in some of the heavier snow showers. Road temperatures suggest
that slippery spots will not be common, but conditions could
worsen somewhat after sunset. Expect drier weather after
midnight when the cyclonic flow may weaken as winds back about
20 degrees.
Temperatures will be cold, with lows in the mid and upper teens,
and wind chills in the single digits above zero.
&&
.SHORT TERM /SATURDAY NIGHT/...
Saturday begins dry with high pressure building to the south.
That will change late Saturday afternoon and Saturday evening
thanks to a short wave disturbance in the mid level flow. Models
have been relatively consistent regarding this system, showing
light snow accumulations mainly along and south of the Ohio
River. 1 to 1.5 inches of accumulation are indicated by the
latest model estimates in those southern locations such as
Owenton and Maysville KY, with lesser amounts forecast as we go
farther north to Dayton and Columbus. There may be some travel
impacts to the southern areas by Sunday morning.
Temperatures staying below normal are forecast to rise to the
upper 20s to mid 30s Saturday, falling to the upper teens to mid
20s Saturday night.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
On Sunday morning, broad troughing will remain in place across
the eastern half of the CONUS, with a shortwave moving through
the Ohio Valley and into the mid-Atlantic region. The broad
trough will dominate the weather pattern through the extended
forecast period, with temperatures below normal being the main
issue. There may be a brief warm-up heading into Thursday,
before cold conditions settle in again for Friday and likely
beyond.
The Sunday morning snow will be exiting the area by early afternoon,
with only light additional accumulations in the southeastern ILN CWA
before ending.
The next chance for precipitation will be late Tuesday night into
Wednesday. After the broad trough finally moves to the east, a brief
but notable period of height rises will occur, with theta-e
advection -- primarily at 850mb and above. This mid-level forcing
will be focused to the north of the ILN area, but it is expected
that some precipitation will spread into the region from northwest
to southeast. The main issue with this precipitation will be
determining the precipitation type. Initially, the boundary layer
will be cold enough to support all snow (through Wednesday morning)
before some switch to rain occurs where temperatures are able to
warm on Wednesday, as the thermal profile switches from an inversion
to one with steeper lapse rates. It is not totally out of the
question that some chance for light freezing rain could occur with
this kind of pattern developing over cold antecedent conditions, but
probabilities for this to occur -- on a Day 5 forecast -- remain
small. The main story for Wednesday morning at this point is that
some wintry precipitation will be possible, but with little
confidence in any notable impacts. After this precipitation ends
late Wednesday, some additional precipitation chances may come into
the picture for the end of the week.
This brief warm-up on Wednesday and Thursday will only bring
temperatures back to values near normal -- or even maybe just short
of normal. By the end of the week, another southward moving cold
front will bring a return to temperatures well below normal.
Winds are worth noting through the extended period as well. As the
mid-week system moves through the area, this will be the period with
the tightest pressure gradient, as a surface low moves across
Michigan. Current models suggest this will be on Wednesday, with
some potential for gusts in the 20-30 knot range.
&&
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
Light to moderate snow showers continue to move through the
region, primarily affecting the northern TAF sites. These
showers continue through midnight, then taper off. Winds remain
elevated as we head into the first half of the night, with gusts
to 25 knots possible through 02z ish. Then, gusts decrease and
we're left with WNW winds around 10 knots.
After snow moves east, conditions improve to VFR for all sites.
Clouds clear out and we'll be left with some scattered cu for
the early morning on Saturday, persisting into the afternoon.
Winds increase yet again, shifting to westerly around 12 knots,
gusting to 25 knots through Saturday afternoon.
Clouds begin to thicken and lower as we head into the late
afternoon hours Saturday ahead of our next weather maker that
arrives Saturday night. For now, have trended this into all TAF
sites and included arrival of snow showers, MVFR and IFR
CIGs/VSBYs into the extended CVG TAF.
OUTLOOK...MVFR/IFR conditions possible Saturday night into
Sunday, particularly for sites along/near the Ohio River.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...None.
KY...None.
IN...None.
&&
$$
SYNOPSIS...Coniglio
NEAR TERM...CA/Coniglio
SHORT TERM...Coniglio
LONG TERM...Hatzos
AVIATION...CA
Source:
ILN issues Area Forecast Discussion (AFD) at Nov 29, 9:19 PM EST---------------
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