ILN issues Area Forecast Discussion (AFD) at Jan 4, 8:55 PM EST068
FXUS61 KILN 050155
AFDILN
Area Forecast Discussion
National Weather Service Wilmington OH
855 PM EST Sat Jan 4 2025
.SYNOPSIS...
A low pressure system will move east across the Ohio Valley
Sunday into Monday. With a cold airmass in place, a significant
winter weather event is expected. A very cold airmass will
settle into the region behind the system through mid week.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
High and mid clouds will spread across the region overnight. As
clouds thicken, temperature drop will cease. Little change to
lows.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY/...
By Sunday morning, the WAA-induced banded pcpn will be
expanding to our SW, with strong H8 frontogenesis developing across
the mid MS Rvr Vly and SW OH Vly during the morning hours. While
pcpn will expand to the NE into the local area by late morning, LL
sfc flow will initially be quite dry (dewpoints in the single
digits) and with winds out of the NE, the dry air will be somewhat
difficult to rapidly erode on the leading edge through early
afternoon. In fact, it is this dry air in the lowest several
thousand feet which may delay onset of snow further to the N near I-
70 a few hours beyond previous fcst cycles.
For Sunday afternoon through the evening (20z-06z), confidence
is high in a band of WAA/isentropic-lift driven heavy snow
pivoting to the NE into the local area, particularly after 18z.
There is quite a bit of concern, particularly in N KY, EC/SE IN,
and the Tri-State area extending into SW OH and the Miami
Valley, for a period of very heavy snow (hourly rates >=1")
within the 20z-06z time frame. This potential is shown well via
the HREF snowband prob tracker data set. During this time
(especially from 00z through 06z), should be tremendous overlap
of deep-layer moisture and strong lift within the DGZ,
supporting a thumper of a snow band in the SW half of the area
prior to 06z. This will likely create very difficult, if not
impossible, travel conditions for Sunday evening near/S of I-70,
with lighter rates/amounts favored N of I-70 through 06z. It is
within this late afternoon/evening time frame that locales in
the Tri-State into N KY and SC OH will receive the /bulk/ of
their snow for this event, with many locales receiving in excess
of 6" within this ~8hr time frame.
As we progress into the 06z-12z time frame, the thumper of a
snow band should continue to pivot to the NE, aligning closer
to/N of I- 70 and becoming more elongated from W-E, with the
heaviest snow from WC through central OH getting going
near/after midnight. The time period for heaviest snow rates
from WC through central OH is likely to be within the early part
of the 06z-12z time frame Monday before lighter rates evolve
after 08z as the band stretches out from W-E. Further to the SW,
for the Tri-State area and N KY to just S of I-70, there is a
/strong/ signal for an abrupt loss of moisture within the DGZ
near/after 06z, suggesting that we will lose ice nucleation and
the ptype will transition to mainly freezing drizzle and/or
light FZRA/IP by 08z. This is an aside from whether the profile
(H7- H8 layer) actually goes above freezing, which still seems
probable for locales S of the OH Rvr. But... even N of the OH
Rvr from EC/SE IN through SW/SC OH, the loss of moisture in the
DGZ will be the primary factor regarding a decrease in SN
coverage/intensity past 06z, with latest data suggesting that
there may not be much snow (if any at all) beginning around
06z through at least 12z Monday, even in a completely
freezing/subfreezing profile. A prolonged period of freezing
drizzle or light FZRA/IP is probable in these areas between
06z-12z, likely persisting through 15z for locales E of I-75
before better moisture attempts to filter back in from the W
within the deformation axis past 15z. Quite frankly, the
prospect of having light freezing rain/drizzle with sfc air
temps ranging from 20-26F is concerning, with light rates
supporting efficient accretion through a 6-10 hour time frame.
There is the possibility that the near-sfc (i.e. sfc to about
775mb) profile is cold enough/deep enough that IP may end up
being the predominant mixed ptype. This being said, as of right
now, we are expecting the highest ice accumulations to generally
still be S of the OH Rvr, particularly from Carroll to Lewis Co
KY (and points further S) where several tenths of an inch of
ice are possible. This, with a tightening pressure gradient and
increasing winds toward daybreak and beyond, lends itself to a
situation that will become increasingly favorable for some
isolated to scattered tree damage and power outages near/S of
the OH Rvr.
After 12z-15z Monday, as the sfc low pulls E of the region, a
deformation axis of snow should pivot back in from the W into the
local area, particularly after 15z. This should yield some
additional (lighter) snow from mid morning through mid afternoon
before the snow tapers off from W to E past 21z. Snow amounts after
12z Monday should generally range from 1-3" area-wide (highest
amounts favored S of I-70), on top of what fell prior to 12z, which
will likely be 6+" for many spots S of I-70. Regardless of whether
it will be lightly snowing (N of I-70) or lightly FZRA/freezing
drizzle (near/S of I-70) at 12z Monday, the morning commute will be
significantly impacted for the entirety of the region.
The latest data suggests a corridor between I-70 and N KY where snow
amounts on the order of 5-10+ inches is expected. A foot of snow is
not out of the realm of possibilities for a few spots within this
corridor. There is high confidence in a very sharp gradient on the
nrn fringe N of I-70, with snow accumulations likely to vary by
several inches across only a 20-30 mile N-S distance on the nrn
edge. This should set up in the vicinity of an axis from Darke Co OH
to Licking Co OH, where 3-6" is expected (higher amounts favored in
southern parts of respective counties). Further to the N in WC OH,
even lighter amounts of generally 1-3" are favored from Mercer Co OH
to Hardin Co OH.
NE winds will gradually increase Sunday night to 15-20kts, with
gusts close to 25kts, evolving during the day Monday as the low
pressure begins to pull to the E. Should significant ice amounts on
the order of one quarter of an inch or greater accumulate in N KY or
far SC OH , the gustiness during the day Monday will only exacerbate
potential power outage concerns. So this portion of the forecast
will be monitored closely.
&&
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Main weather threat through the extended period will be very cold
temperatures and wind chills, especially for the middle of this
week... with high temperatures in the upper teens to low twenties
and lows reaching from near zero to the single digits above zero.
Due to the fresh snow cover, it is possible some of our sheltered
or rural areas could drop to the single digits below zero.
A weak weather system will move across the Gulf Coast States
Friday into Saturday. A northern stream trough lagging behind this
system could bring some light snow across the Great Lakes and Ohio
Valley Friday night. While deep moisture is not likely to be
available for heavy snow, will need to continue to track this system
for some light accumulations in the very cold airmass in place at
that time.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
VFR will prevail past 12Z with just increasing high and mid
clouds. Snow will spread in from the southwest, affecting the
Cincinnati terminals after 15Z. This will cause visibilities
and ceilings to fall to IFR fairly quickly. The snow will be
slow to make further progress across the region during the day,
affecting KILN towards 21Z and KDAY near the end of the period.
The Columbus terminals will remain VFR.
OUTLOOK...IFR to LIFR/VLIFR conditions will occur Sunday night
into Monday. There will be a wintry mix Sunday night changing
back to all snow Monday. MVFR ceilings may linger Monday night
into Wednesday.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...Winter Storm Warning from 10 AM Sunday to midnight EST Monday
night for OHZ060>065-070>074-077>082-088.
Winter Weather Advisory from 1 PM Sunday to midnight EST
Monday night for OHZ026-034-035-042>046-051>056.
KY...Winter Storm Warning from 10 AM Sunday to midnight EST Monday
night for KYZ089>100.
IN...Winter Storm Warning from 10 AM Sunday to midnight EST Monday
night for INZ050-058-059-066-073>075-080.
&&
$$
SYNOPSIS...KC
NEAR TERM...
SHORT TERM...KC
LONG TERM...
AVIATION...
Source:
ILN issues Area Forecast Discussion (AFD) at Jan 4, 8:55 PM EST---------------
If I'm using your data in a way that is against your terms please email the team at "threatweb@pupswoof117.com"! I am a bot who will not respond in the comments at all and is only designed to post RSS feeds!
