CLE issues Area Forecast Discussion (AFD) at Nov 18, 9:24 AM EST090
FXUS61 KCLE 181424
AFDCLE
Area Forecast Discussion
National Weather Service Cleveland OH
924 AM EST Mon Nov 18 2024
.SYNOPSIS...
A weak frontal boundary will settle south across the area this
morning before tracking back north as a warm front tonight.
An area of low pressure will develop over Great Lakes region on
Wednesday, pulling a strong cold front east across the area.
This low will meander across the eastern Great Lakes before
moving off to the east coast on Friday.
&&
.NEAR TERM /THROUGH TUESDAY/...
Visibilities will continue to improve near the Toledo area where
we saw a little patchy fog this morning. Most areas will be
cloudy today with a few breaks in the clouds, mainly in the
east.
Previous discussion...A weak frontal boundary will move south
across Lake Erie this morning, bisecting the forecast area by
this afternoon. Low ceilings and reduced visibilities in
Northwest Ohio should clear by by 11 am. Areas of low stratus
will accompany this front as it moves just south of Lake Erie
this afternoon with scattered/broken cloud cover through the
day. Warm temperatures are expected today with highs about 10
degrees above normal.
The frontal boundary will lift back northeast tonight in
response to a low pressure system lifting northward across the
Great Plains to the Upper Midwest region. A line of convection
that develops well to our west this afternoon will approach late
tonight, moving across the area during the daytime hours on
Tuesday. Confidence in rain has increased along with an increase
in QPF amounts as well, with areawide max PoPs of 80-90% and
rainfall amounts of 0.25-0.4" west of I-71. Rain showers should
gradually dissipate and decrease in coverage through the
afternoon as precipitation outruns the synoptic forcing.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
An active forecast period is in store, particularly from Wednesday
afternoon through Thursday when the potential exists for impactful
winds and wet snow accumulations. Confidence in the placement and
magnitude of those impacts remains low given inconsistent details
among models, but we'll dive into the details and what could lead to
a more or less impactful system below.
A cold front that will be bisecting the area Tuesday evening and
will continue slowing its eastward progression while undergoing
frontolysis through Wednesday morning. Have 20-50% POPs for rain
showers continuing Tuesday night, highest from eastern OH into PA,
with light amounts of QPF in the forecast. The front will probably
stall somewhere over our eastern Ohio counties late Tuesday night
into Wednesday before dissipating on Wednesday as the stronger
system begins organizing to our west. Lows Tuesday night are
expected to generally range from the mid 40s to lower 50s, with
light winds and minimal cold air advection behind the weakening
front. There should be a relative lull in weather Wednesday morning
with mostly cloudy skies, mainly dry weather, mild temperatures and
light winds before attention quickly turns to our west.
In a big picture sense, there is decent agreement and consistency
for the Wednesday afternoon through Thursday night timeframe. A very
amplified pattern will be in place, with high-latitude blocks over
the northern Pacific and northeastern Canada/Greenland pinning a
series of deep, slow-moving troughs underneath them in the mid-
latitudes. One of these troughs will move out of the Midwest and
into the southern Great Lakes/Ohio Valley on Wednesday, with the
trough deepening Wednesday night into Thursday while drifting east
towards the northern Mid Atlantic and southern New England by
Thursday night. At the surface there's high confidence that we will
see a strong cold front sweep across the area during the day
Wednesday, with low pressure developing either overhead or to our
north/northeast and deepening Wednesday and Wednesday night. This
low pressure is expected to transfer its energy to a developing low
near the NY/NJ coastline into Thursday, leaving broad surface
troughing hanging back into the Great Lakes. There's good agreement
that a pool of 850mb temperatures of -5C to -10C will work through
the region on the southwestern side of the developing low Wednesday
night and persist into Thursday, with temperatures aloft gradually
warming from the north starting Thursday night as the system becomes
completely wrapped up and starts drifting east. There's also good
agreement that there will be a notable swath of precipitation
southwest of the deepening low Wednesday night into Thursday before
becoming more showery as the bulk of the energy transfers towards
the East Coast, with at least some of that swath of precip falling
as wet snow where the lift near the low interacts with the pool of
colder air wrapping in from the southwest. There's also decent
agreement that it will be windy with and just behind the frontal
passage Wednesday afternoon and evening, with winds continuing to
the southwest of the deepening low Wednesday night into
Thursday.
Users who viewed the 0z GFS and 0z NAM/European models are now
saying "but those two solutions aren't even close!"...and we
certainly take note of that. The big question is exactly how far
south does the closed low aloft dig Wednesday into Thursday, and
exactly where and how quickly does surface low pressure deepen
starting during the day Wednesday. The GFS model maintains a focus
on the energy in the north portion of the upper trough and tracks
the overall closed low farther north. This leads to surface low
pressure that deepens slower and tracks farther north, a much weaker
solution overall that takes the heavier precip (accumulating snow
potential) safely north of our area with much less wind overall. The
NAM, European, and Canadian all key in on energy rotating around the
southern portion of the trough on Wednesday, leading to closed low
aloft tracking overhead or just to our south through Wednesday
night. This leads to low pressure that deepens much quicker and much
closer to our local area, bringing greater precipitation (and
accumulating snow potential) into our area and leading to a much
windier storm overall. This is particularly true of the 0z NAM and
European model runs. When looking at the ensembles to try to make
sense of these different solutions, the Canadian ensemble has
consistently had this farther south solution, with the European
ensemble trending that direction each run over the last 24 hours.
The GFS ensemble has a solution more closely mirroring the
operational run. There are members of all 3 ensembles supporting
anything from a GFS-like solution with relatively modest amounts of
wind/wet snow in the local area to a solution even stronger/more
amplified than the NAM/Euro solution. So, it is hard to lean too
much in one particular direction. Given what appears to be the
European ensemble inching towards the farther south, stronger,
potentially snowier outcome did swing the forecast slightly windier
and wetter Wednesday afternoon through Thursday. However, notable
adjustments in either direction could easily still be needed.
Temperatures should peak in the 50s to near 60 on Wednesday ahead of
the front, warmest east. Lows Wednesday night will be in the 30s,
with the higher terrain potentially reaching freezing while
locations closer to the lake stay in the mid to upper 30s. Highs on
Thursday will be in the mid to upper 30s for many away from Lake
Erie, with near 40 along the lakeshore. Lows Thursday night will be
similar to or perhaps slightly milder than Wednesday night,
generally in the low to mid 30s inland (locally below freezing in
the higher terrain) to the upper 30s near Lake Erie. Any snow that
falls will be wet and will most favor locations inland from the lake
and in the higher terrain given these expected temperatures.
To sum up the potential wind impacts, there will be an initial surge
of gusty winds behind the cold front Wednesday afternoon and
evening. A line of convective showers may evolve along the front,
which could enhance any wind potential with the front. Weaker
solutions, such as the GFS, would probably support sub-advisory
gusts of 35-45 MPH right behind the front. Stronger solutions, such
as the NAM and Euro, would support advisory-criteria type gusts of
45-55 MPH with and right behind the front. A GFS-like solution would
continue breezy but sub-advisory (think gusts in the 30-35 MPH
range) through Thursday night at times as low pressure deepens well
to our north. A more aggressive NAM/European-like solution would
likely support continued potential for advisory to warning-level
gusts (think in the 55-65 MPH range) Wednesday night into early
Thursday southwest of a rapidly deepening low pressure. The range of
possible wind impacts is from "no headlines" to "potentially warning-
level" gusts. NBM probabilities currently depict a 30-50% risk of
advisory-criteria gusts across the local area and a 5-25% risk of
warning-level gusts at some point with this entire system. It's
worth noting that the official forecast, taking into account a wide
array of models and ensembles and incorporating bias-correction,
does not currently have any gusts over advisory-criteria despite the
higher-end solutions posed by the NAM/European models.
To sum up the potential snow/winter impacts, the airmass should be
cold enough for at least some snow to mix in overnight Wednesday
night through Thursday away from Lake Erie. By Thursday night into
Friday, milder air wrapping in from the north should gradually lead
to precipitation changing back to primarily rain from north to
south. The big question is where does the low wrap up Wednesday
night into Thursday, which will dictate where a heavier swath of
precipitation that would support wet snow accumulations will set-up.
Like the operational models, ensemble members range from placing
that swath of potential accumulating snow over our area (or even
just southwest) to having a weaker solution that produces much less
snow focused to our north or northeast. NBM ensemble probabilities
for snow accumulations over 1 inch during this period are 20-50%
across most of our area away from the immediate lakeshore, with
locally 50-60% in the higher terrain. Odds for over 4" are lower,
generally ranging from 10-20% in the higher terrain near Mansfield
points east-northeast across interior Northeast OH and Northwest PA.
Odds for 6-8"+ are not zero but continue to trend lower, generally
10% or less and focused in the higher terrain. The latest NBM has
not incorporated all of the 0z ensembles yet, so probabilities may
rise a bit in future runs, though again it's worth noting that
despite the gaudy solutions posed by the European/NAM that there is
a ton of uncertainty. The official forecast does have light snow
accumulations of up to an inch or so in the higher terrain away from
the lake, with little to none close to the lake. There's plenty of
room to trend to a more impactful solution and we will be here to
adjust as needed, but given the negative factors (warm ground,
marginal air temperatures, narrow swath of snow) and overall
uncertainty it is extremely important to take deterministic model
snow outputs available on the internet with a massive grain of
salt.
&&
.LONG TERM /FRIDAY THROUGH SUNDAY/...
Chilly cyclonic flow will persist through the weekend as troughing
lingers over the Northeast US. Expect hit-or-miss showers area wide
on Friday with much greater persistence of showers east of Lake Erie
due to lake enhancement. We should start gradually trending drier
from the southwest through the weekend as high pressure slowly
builds in, though with the ridge axis not moving overhead until
Sunday or Sunday night lake effect will continue until that time
downwind of the lake. Precip should mainly be a chilly rain this
period, though a secondary surge of colder air arriving around
Saturday may allow some snow to again mix in with the rain showers
across inland locales. Temperatures will be cooler than normal
through the weekend with west-northwest breezes slowly relaxing.
&&
.AVIATION /12Z Monday THROUGH Friday/...
A weak cold front has moved south of Lake Erie with a low
stratus deck being ushered in from the north. MVFR ceilings
expand from the fringes of Northwest Ohio all the way move to a
good portion of Northeast Ohio and all of Northwest
Pennsylvania. Ceilings are generally in the 1-2kft range but a
few pockets of IFR have developed and are expected to continue
to develop over the next few hours.
A separate warm front moves in from the southwest later this
evening into the overnight hours tonight, accompanied by a band
of clouds and isolated rain showers. Ceilings with this warm
front will vary in the 2-4 kft range.
A cold front approaches from the west Tuesday morning, with a
line of rain showers overspreading the area. Rain may be
reaching the I-75 corridor around 11-12Z, with visibilities and
ceilings quickly dropping to at least MVFR shortly thereafter.
Wind generally light and variable, although southeast winds
start to increase Tuesday morning, especially for western TAF
sites.
Outlook...Non-VFR is expected with rain showers Tuesday. A
large low pressure is expected to impact the region Wednesday
through Friday, bringing breezy conditions and periodic non-
VFR in rain showers, potentially mixed with wet snow showers at
times.
&&
.MARINE...
West-northwest winds will be elevated a bit at 10-15 knots east of
Cleveland this morning before becoming much lighter this afternoon
as high pressure slides through. East-southeast winds pick up to 10-
20 knots tonight into Tuesday morning ahead of a warm front lifting
towards the lake. Winds shift southerly during the day Tuesday
behind the warm front and then more west-southwest Tuesday night
into early Wednesday as a weakening cold front crosses the lake.
Winds will weaken a bit to 10-15 knots Tuesday night. While there
will be some chop at times, no marine headlines are currently
anticipated through Wednesday morning.
A prolonged period of unsettled marine conditions is still expected
beginning Wednesday afternoon and lingering through the weekend. A
strong cold front will sweep across the lake Wednesday afternoon and
evening. A period of 20-30 knot west-southwest winds is likely right
behind the cold front. Low pressure will then deepen near the lake
or a bit to the north/northeast Wednesday night and Thursday,
turning winds more west-northwest and keeping them elevated. The
location and rate of intensification of the low is not agreed-upon
by models yet. At the least, continued 20-30 knot winds appear
likely Wednesday night into Thursday morning across the lake.
However, a stronger low pressure would support gales, with current
NBM ensemble probabilities depicting a 30-60% risk for sustained
gales over the central and eastern basins at some point Wednesday
night or Thursday (10-30% in the western basin). Low pressure will
transfer to the East Coast at some point on Thursday, though brisk
northwesterly cyclonic flow in the 20-30 knot range will likely
continue through Friday night. Winds will remain elevated out of the
west-northwest but should gradually subside starting Saturday. A
prolonged Small Craft Advisory is a given beginning at some point
Wednesday and lasting well into the weekend. Potential for gale
headlines is less confident but worth monitoring, especially
Wednesday night into Thursday though with winds possibly remaining
close to gale at times through Friday night with stronger
solutions.
&&
.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
MARINE...None.
&&
$$
SYNOPSIS...Saunders
NEAR TERM...KEC/Saunders
SHORT TERM...Sullivan
LONG TERM...Sullivan
AVIATION...Saunders
MARINE...Sullivan
Source:
CLE issues Area Forecast Discussion (AFD) at Nov 18, 9:24 AM EST---------------
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