-- Discussion containing changed information from previous version are highlighted. --
378
FXUS61 KCLE 191059
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
659 AM EDT Thu Sep 19 2024

.SYNOPSIS...
A ridge of high pressure will strengthen across the Great Lakes
today and Friday. A weak cold front will approach Friday night
before dissipating as the ridge remains in control through the
weekend. Low pressure moving into the western Great Lakes
Monday will extend a cold front into the region.

&&

.NEAR TERM /THROUGH FRIDAY/...
6:30 AM Update...

Patchy fog has expanded this morning across NW and north central
Ohio and the central highlands. Most visibilities are 1 to 3
miles, but several sites are at one half mile, with KTOL
checking in with 1/4 mile. This will continue through 12 or 13Z
then should quickly dissipate. The forecast remains unchanged.

Original Discussion...

Patchy dense fog is expected to expand through sunrise due to small
temp/dew point spreads, light winds, and clearing skies. The
coverage will be greatest in NW Ohio and in the central highlands
where clear skies will interact with the smallest temp/dew point
spreads. Issued an SPS through 14Z for these areas. Fog will
gradually dissipate through mid morning.

The story of the past 10 or so days will continue through the end of
the week...unseasonably warm and dry. In fact, temperatures will
trend even warmer as mid/upper ridging and warm air advection
strengthens across the region.

Starting off this morning, the old closed low that meandered around
the Appalachians the past 2 days is drifting east and is now
centered over eastern North Carolina. Upstream, another closed low
is drifting along the US/Canadian border centered near northern
North Dakota. This upstream closed low and associated mid/upper
shortwave trough will lift well north into Canada tonight and Friday
while deamplifying as a stronger closed low/trough progresses from
southern California today into the desert Southwest by Friday night.
This stronger system will force strong downstream height rises
across the Ohio Valley and Great Lakes regions today through Friday
leading to a sharpening mid/upper ridge that will finally nudge the
Carolinas closed low offshore by late Friday. A piece of shortwave
energy on the southern edge of the aforementioned closed low lifting
into Canada will push a weakening cold front into Lower Michigan
Friday, but this boundary will largely wash out as it runs into the
building ridge.

In terms of what this all means for the forecast, strong surface
high pressure over New England will continue to have the most
influence today with continued E to NE flow, but skies becoming
mostly sunny as the Carolinas closed low exits will allow for warmer
temperatures. Expect highs to reach the low 80s areawide, with some
mid 80s in NW Ohio where warm air advection starts to kick in. By
Friday, the building ridge and stronger warm air advection will
boost highs in the low/mid 80s areawide, with upper 80s in NW Ohio.
Kept all areas dry for now as the weakening front approaches, with
any widely scattered showers in NW and north central Ohio holding
off until Friday night. Lows tonight will range from the mid 50s to
low 60s with good potential for patchy fog again since winds will be
light and temp/dew point spreads will be small.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
A shortwave will try to over top an upper ridge across the region on
Friday night. With dew points in the 60s and some lift with this
wave, have some low PoPs in Northwest and North Central Ohio on
Friday night. Do not believe that any precipitation will be
impactful, but there could be some radar returns. The ridge remains
in place for Saturday and another hot and generally dry day will be
expected with temperatures in the mid to upper 80s. There could be
some returns that develop in NE OH and NW PA on Saturday off a
weakened boundary from any of Friday`s activity. In the end, the
rain chances remain low. A stronger shortwave will push over the
ridge on Sunday and bring a cold front toward the forecast area.
Believe that the NBM is too aggressive on the PoPs for the daytime
hours on Sunday and have tapered them down slightly. However, the
front should start entering on Sunday night and have the first 40
PoP in a while for the forecast area. Temperatures on Sunday will
remain warm into the 80s ahead of the front.

&&

.LONG TERM /MONDAY THROUGH WEDNESDAY/...
The long term forecast period introduces a new pattern into the
region with a pair of shortwaves effectively eroding the upper ridge
over the region and supporting a cold front through the area, which
will bring increasing rain chances. The main trough axis with the
shortwaves will be the best timing for the best rain chances, or
Monday and Wednesday afternoons at this time and have increased PoPs
to 40 percent. There are some subtle time differences among the
extended guidance to preclude higher PoPs for now, but can see PoPs
increasing in future forecasts to support the best chance of rain in
almost 2 weeks. With a cold front through the area on Monday, expect
temperatures to dip into the 70s for next week.

&&

.AVIATION /12Z Thursday THROUGH Monday/...
-- Changed Discussion --
Fog is pretty persistent at KTOL, KFDY, and KMFD early this
morning, so increased the fog in those TAFs through 13Z then it
should rapidly dissipate. Otherwise, just enough wind and higher
temp/dew point spreads has stopped fog from developing farther
east, so expect the other sites to avoid it this morning. VFR
will continue today once the fog burns off with high pressure in
control, but conditions look favorable for additional fog
tonight in NW and north central Ohio. Took KTOL, KFDY, and KMFD
to MVFR for now, but these will likely trend lower since a
similar pattern to last night will be in place tonight.

Light and variable winds early this morning will become E to NE
and increase to 5-10 knots by mid morning into the afternoon
before turning light SE tonight.

Outlook...Primarily VFR expected through Sunday. Non-VFR
possible in showers Sunday night and Monday, but this is low
confidence for now.
-- End Changed Discussion --

&&

.MARINE...
The marine forecast for today will be very similar to the last
several with the lake being on the western periphery of high
pressure. This will support southeast to easterly flow across the
lake before lake breezes develop and a stronger push of northeast
flow moves through for the afternoon hours. A decaying cold front
will move through the region on Friday. The feature generally
remains unimpressive and the weak pressure gradients across the
region should allow for one more day of light east to southeast
winds that will shift to the northeast with lake breezes. A cold
front and associated low pressure system will enter the Great Lakes
region slowly for early next week. Offshore flow will be favored
ahead of this feature for the weekend but there could continue to be
some lake breeze development to shift some wind directions. The
front will approach next week and allow for some enhanced
southerlies before the boundary crosses and northeast flow becomes
favored. In the end, there could be some marginal windows for a
small craft headline, but the overall pattern seems quiet for the
lake.

&&

.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
MARINE...None.

&&

$$

SYNOPSIS...Garuckas
NEAR TERM...Garuckas
SHORT TERM...Sefcovic
LONG TERM...Sefcovic
AVIATION...Garuckas
MARINE...Sefcovic