876
FXUS62 KILM 212112
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
412 PM EST Tue Jan 21 2025

.SYNOPSIS...


Frigid temperatures continue tonight as an area of low pressure
strengthens offshore tonight. Snow, some sleet mixed-in along
the coast will produce hazardous travel on Wednesday and into
Thursday as temperatures remain mostly below freezing. Hazardous
travel will likely continue through the remainder of the week.
Seasonable temperatures will finally return over the weekend.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
Models have trended wetter and farther northwest today with an
area of low pressure off of the Carolina coast tonight. Snow
totals have increased significantly since this morning with
portions of coastal NC/SC now expecting close to 6 inches of
snow and sleet. The Winter Storm Warning has been expanded
across the entire forecast area with 1 to 3 inches of snow
expected near the I-95 corridor, 2 to 4 inches between I-95 and
the coast, 3 to 5 inches near the coast, and 2 to 4 along the
immediate coastline where some mixing may occur. Periodic
banding will produce a few areas with isolated higher amounts,
especially near the coast where mixing does not occur. High-end
totals around 6 or 7 inches, primarily in the Cape Fear region
and up to 5 inches just inland.

With this northwestward shift, we are concerned about warmer
temperatures aloft and sleet mixing with snow along the
immediate coast. Warm advective processes and isentropic lift
will likely lead to some form of mixed precip for portions of
the Grand Strand and Brunswick County beaches this evening.
However, soundings indicate that this warm nose is small,
generally around 0.5-1 degree above freezing. While this is
enough to produce some p-type issues, it does not account for a
heavier precip rate and the melting within a miniature warm
nose.

It is possible that this warm nose is muted by an isothermal
layer which will maintain mostly snow and only a brief period
of snow pellets or sleet. There is some confidence with this
prediction as 850 mb winds turn westerly by 02-04Z with a
secondary low developing along the Gulf Stream this evening. Dry
and cold air advection within this layer should promote further
melting and an isothermal profile with mostly snow. Signs of
this are evident as the NAM and hi-res models produce a 0C 850
mb line as far east as the western edge of the Gulf Stream,
indicating deep cold air pushing offshore late tonight. All
this to say that the expected forecast attempts to lean toward
mostly snow, but lower totals are possible. The Grand Strand
area does include a brief period of mixing which lowers totals
by an inch or so, but this could be cut even further by mixing.

Hazardous travel and frigid temperatures will be the primary
concern tonight and Wednesday once the precip comes to an end.
Clouds tomorrow morning will limit any potential melting early
in the day and temperatures are unlikely to get much above
freezing with some partly sunny skies later on. Wind chills
tomorrow morning will start around 10 degrees and hover in the
low to mid teens throughout the day. What melting does occur
will quickly refreeze around sunset prolonging hazardous driving
conditions into Thursday.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
Lows Wednesday night will be cold to say the least, with a Cold
Weather Advisory likely being needed. I`ve gone a couple
degrees below guidance to account for the uptick in snowfall
totals in the near term paired with temperatures remaining near
freezing into the short term period. Should snow melt faster
lows could be a bit warmer Wednesday night. The focus for the
period then shifts to possible freezing rain along the coast
Thursday. Some guidance is still hinting at enough low level
moisture holding on through early Thursday as temps remain below
freezing with a warm nose aloft. The issue will be the arrival
of dry air from the northwest and the warming during the day,
which will put wintry precipitation chances to an end through
the rest of the day. Compared to previous forecasts, the trend
is downwards for freezing rain with rain being more likely. The
highest chances for some freezing rain (still around 20%) will
be at the coast. For Thursday night, amidst decreasing rain
chances and persistent clouds, lows will be in the lower 20s but
with much lighter winds. For now, a Cold Weather Advisory
doesn`t appear likely for Thursday night.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Dry with a slight warming trend through the weekend as high
pressure builds in from the west and we sit under zonal flow. As
the high slips offshore, we could see an increase in rain
chances headed into early next week as a shortwave moves through
aloft and moisture creeps in from the southwest.

&&

.AVIATION /21Z TUESDAY THROUGH SUNDAY/...
VFR conditions are expected this afternoon. MVFR worsening to
IFR this evening as snow begins before 00Z and increases in
intensity tonight. Heavier snowfall rates overnight will bring
visibility to IFR after 03Z, approaching minimums near the coast
where periods of heavy snow will be possible. Some mixing with
snow pellets and sleet will likely occur along the immediate
coast, but the dominant p-type will remain snow. Dry air builds
across the region tomorrow morning and IFR will quickly become
VFR with clearing skies after noon.

Extended Outlook... Back to VFR Wednesday afternoon. Another
system could cause flight restrictions on Thursday into Friday.

&&

.MARINE...
Through Wednesday... As an area of low pressure strengthens
offshore, winds will increase tonight and hazardous conditions
are expected to develop this evening. In addition to winds, seas
will increase to 4-6 feet. Snow, sleet, and rain farther
offshore will also add to navigation difficulties. Winds remain
strong on Wednesday with frigid temperatures, wind chills in the
single digits.

Wednesday Night through Sunday... Improving marine conditions
through the period, especially into the weekend with building
high pressure. N flow 10-15 kts will become more variable as
high pressure slips offshore late this weekend. Waveheights will
decrease from 3-5 ft to 2-3 ft by Friday and then further
decrease to 1-2 ft as the high moves overhead for the weekend.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
NC...Winter Storm Warning from 9 PM this evening to 8 AM EST
     Wednesday for NCZ087-096-099-105>110.
     Cold Weather Advisory from midnight tonight to 11 AM EST
     Wednesday for NCZ087-096-099-105>110.
SC...Winter Storm Warning from 9 PM this evening to 8 AM EST
     Wednesday for SCZ017-023-024-032-033-039-054>056-058-059.
     Cold Weather Advisory from midnight tonight to 11 AM EST
     Wednesday for SCZ017-023-024-032-033-039-054>056-058-059.
MARINE...Small Craft Advisory from 9 PM this evening to 2 PM EST
     Wednesday for AMZ250-252-254-256.

&&

$$

SYNOPSIS...ILM
NEAR TERM...21
SHORT TERM...LEW
LONG TERM...LEW
AVIATION...21
MARINE...21/LEW