Area Forecast Discussion
Issued by NWS Wilmington, OH

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000
FXUS61 KILN 161800
AFDILN

AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
100 PM EST Sat Feb 16 2019

.SYNOPSIS...
High pressure will move into the Great Lakes today, bringing dry
conditions through the Ohio Valley. A weak area of low pressure
will bring some mixed precipitation through the area on Sunday.
with dry weather expected again on Monday and Tuesday. The next
chance for precipitation will be on Wednesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Lower level clouds have been advecting southwestward and based
on visible satellite, it looks like they are trying to fill in
somewhat in the clear areas across southwest portions of our
fa. In continued northeasterly low level CAA, think these
clouds may hang in a little longer through into early
afternoon. The low levels are forecast to dry out as we head
into this afternoon and as the low level CAA becomes more
neutral, will go ahead and allow for some clearing skies later
this afternoon. The northeasterly flow and clouds will also keep
temperatures on the cool side, but afternoon highs will also be
dependent on how fast the clouds dissipate. Will generally
range highs from the low 30s in the north to the upper 30s
across the south.

&&

.SHORT TERM /SUNDAY/...
On Saturday night, a weak mid-level closed low over the
northern plains will begin to open up, as the pattern over the
central part of the country deamplifies. The weakening trough
will begin a quick translation eastward, providing some weak
background ascent to the area by Sunday morning. An area of
surface low pressure is also expected to move northeast out of
the lower Mississippi Valley, crossing through eastern Kentucky
and eventually into Pennsylvania. This will be another source of
forcing for precipitation on Sunday, particularly ahead of (and
north of) the track of the low.

Looking at several models, there is little question that thermal
profiles will support a mix of precipitation types across the
ILN CWA on Sunday morning -- with enough warm air just off the
surface to allow for melting hydrometeors through most (though
not all) of the forecast area. Freezing rain will be the favored
precipitation type along a northward-moving zone from around 09Z
through 18Z through at least (if not slightly north of) the
Interstate 70 corridor. To the north of this zone, snow will be
favored. To the south, regular rain will be favored.

The question, however, is how much precipitation is actually
going to fall within these thermal regimes. The forcing
mechanisms described in the first paragraph of the Short Term
discussion are not strong, nor are the different methods well
aligned. Thus, model QPF depictions have been somewhat
inconsistent with their timing and placement. This may be how
the event plays out, as also supported by the WRF-ARW/WRF-NMM,
with splotchy / patchy echoes gradually drifting northeast
through the area, producing various types of precipitation based
on the thermal profile they are moving through. There is little
confidence in any sort of significant event, or anything that
would require a headline, but certainly some light ice
accumulations will be a possibility. In the far northern CWA,
where snow should remain the dominant precipitation type,
accumulations of up to a half inch are also possible. Notably, t
this is not really a change from the previous forecast, as the
prior thinking still appears valid for the situation.

With the presence of the surface low moving just south of the
area, and frontal development in the vicinity, there should be a
decent gradient in temperatures on Sunday. Max temps are
expected to range from the lower 30s in the north to upper 40s
in the southeast. With a sharp gradient in place, the
specific numbers for temps on Sunday are a little lower
confidence than normal.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
The long term period looks to be an active one across the
region, with several distinct systems poised to have at least
some impacts in the local area -- the first of which will be
pulling east of the Ohio Valley Sunday night, with just a chance
for some lingering light snow across northern Ohio (and perhaps
far northern portions of the ILN FA). Additional snow
accumulations Sunday night (if any) will be relatively light --
on the order of a couple of tenths or so across west-central and
north-central Ohio.

It is important to note that with ample low level moisture in
place, that patchy flurries or even freezing drizzle may develop
Sunday night into early Monday morning. Sounding analysis from
several NWP solutions show best saturation in a layer that would
just be too warm for ice nucleation/crystals during this period
-- so this is a setup that will need to be watched in the coming
 days. Should freezing drizzle development become widespread
 enough, it could have impacts on the Monday morning commute --
 when temperatures will start off in the lower 20s in the north
 and lower 30s in the south.

Quieter weather will evolve during the day on Monday and
continue through most of the day on Tuesday as subtle midlevel
ridging noses northward into the Ohio River Valley and surface
high pressure briefly settles into the Great Lakes region.
Monday highs should be slightly below normal -- generally
ranging from around 30 degrees in the north to around 40 degrees
in the south, with lows Monday night in the upper teens and
20s.

Attention on Tuesday will then turn to potent energy digging
across the central plains which will induce broad southwesterly
flow aloft near and east of the Mississippi River Valley. This
will begin to advect moisture north/east from the lower
Mississippi River Valley into the Ohio Valley, with a surface
low being induced along the attendant /and strengthening/
baroclinic zone. Moisture will begin to stream northeast by
Tuesday evening, with precipitation eventually overspreading the
ILN FA Tuesday night into early Wednesday morning. This setup
poses several concerns -- most notably the fact that moisture
will be running into an antecedent cold airmass -- one that is
not likely to completely vacate the ILN FA before the arrival of
precipitation Tuesday night. While there is still a great deal
of time to hammer out specifics, there is the potential for a
wintry mix of precipitation Tuesday night into early Wednesday
morning as strong WAA advection aloft develops coincident with a
still cold near-surface layer. Although this setup could yield
the entire gambit of winter precipitation across parts of the
area (i.e. freezing rain/sleet/snow/rain), the most likely
scenario right now appears to be something along the line of a
snow to freezing rain to rain progression for at least parts of
the ILN FA. However, at this time and despite model soundings
showing a fairly healthy/deep warm bulge aloft, decided to keep
ptype at either rain or snow during this period even though
freezing rain may end up being the most common ptype based on
current sounding data. It would be far too early to comment on
specific amounts or ptypes for specific areas at this time, but
certainly this system will be watched in the coming days to
determine what kind of impacts may be felt locally.

Either way the precipitation type evolves early Wednesday
morning, temperatures should warm above freezing area wide by
the afternoon (with the freezing line actually working from
south to north even during the early morning hours) , turning
any lingering precipitation to just plain rain. However, even by
the middle of the afternoon , the heaviest precipitation should
be moving east of the ILN FA, with drier conditions returning
for Wednesday night (except for perhaps the far southeast local
area where rain may linger a bit longer).

Another brief break will arrive late Wednesday night into
Thursday before another system develops and impacts the area by
Thursday night into Friday. Although the specifics of this
system, both in timing and evolution, will come into better
focus in the coming days, it does appear another round (or
several rounds) of rain will impact the region towards the end
of the workweek, with temperatures generally trending above
normal late in the week as the unsettled pattern continues.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
MVFR stratocumulus is hanging in across our north. It has been
trying to slowly erode from the south but so far has not made
much progress. Will therefore go ahead and continue with MVFR
cigs at the northern TAF sites over the next few hours. We
should begin to see an improvement as we head through late
afternoon and the low level flow begins to become a bit more
southerly.

We should then get into a period of mainly clear skies heading
into tonight before mid level clouds begin to move back in from
the southwest ahead of the next low pressure system. This low
pressure system will lift northeast across the Tennessee Valley
through the day on Sunday. Ahead of this, precipitation will
spread into our area from the southwest through Sunday morning
as cigs fall into MVFR. The precipitation may start off as a
brief period of snow before transitioning over to freezing rain
and/or rain from the south through mid to late morning.

OUTLOOK...MVFR conditions expected into Monday. MVFR conditions
are possible again Wednesday into Thursday.

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...None.
KY...None.
IN...None.

&&

$$
SYNOPSIS...Hatzos
NEAR TERM...JGL
SHORT TERM...Hatzos
LONG TERM...KC
AVIATION...JGL


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