FXUS61 KCLE 192221

Area Forecast Discussion
National Weather Service Cleveland OH
621 PM EDT Thu Jul 19 2018

A large area of high pressure over the Mid Atlantic region will
push east off the coast tonight. Slow moving low pressure will
track from southern Minnesota tonight into the southern Great
Lakes by Friday night. The low will slowly drift south through
the Ohio valley through the weekend before dissipating early
next week.


no significant changes for the 630 update.

Original discussion...
Quiet weather expected through tonight as high pressure centered
east of the region moves off the Atlantic coast. Cloud cover
will be on the increase late tonight into Friday morning
associated with upstream convection, otherwise no major forecast
changes tonight, with lows generally in the low to mid 60s
across the area.

Main forecast challenge for the near term period is convection
chances Friday and Friday night. Hi-res guidance starting to
paint a clearer picture on convective evolution over the next 36
hours. Showers/storms are expected to fire across northern
Illinois/northwest Indiana around 06Z, associated with the left
exit region of upper jet/nose of low/mid level jet. These storms
should drift across northern Indiana into northwest Ohio after
12Z, and will generally be in a weakening state becoming
divorced from the main forcing and moving into a more stable
environment. The remnants of this convection should move east
across the area through the morning and afternoon, which may
help keep conditions fairly stable across the area through the
day. Have generally went with likely pops moving into the area
after 12Z, with a diminishment to chance range as it expands
east across the area.

A better chance for convection and perhaps some more potent
storms will arrive across the area Friday evening. More storms
are expected to fire across Indiana after 18Z Friday as the
atmosphere destabilizes ahead of more potent surface forcing.
This activity will move into Ohio by 00Z, however the main
question at this point will be the amount of recovery across the
local area to sustain any strong convection. Current feeling is
that any recovery will be limited during the day across the
area, with MLCAPE values remaining less than 1000 j/kg and deep
layer shear remaining minimal with the best jet energy focused
south along the Ohio river. Nevertheless, have another round of
likely pops entering the western part of the area, slowly
diminishing again to chance range across the area through the
night. No big changes to temps Friday and Friday night, similar
to previous forecast and closer to MOS number vs. raw guidance.


Amplification of the upper level ridge over the central United
States will cause deepening of a low pressure system over the
western Great Lakes Saturday. Resultant surface low pressure will
slide slowly south to the Ohio Valley region by Sunday evening.
Moisture will wrap in from the Atlantic to feed the low and hence,
this will bring an extended period for a threat for showers and
thunderstorms to the forecast area. Mixed layer CAPE supports a
threat for thunderstorms across the forecast area through the
weekend. Cool air aloft will likely cause some waterspouts to form
Saturday afternoon into Saturday evening and again on Sunday.
Waterspout nomogram suggests waterspouts will occur during this time
period so will add mention to the lake.

Temperatures through this portion of the forecast period will stay
around normal through Sunday but a bit of warm air advection will
take place Monday and bump temperatures into the middle 80s. No
real push of cool air will take place and overnight lows will be in
the middle 60s.


"Unsettled" still appears the best descriptor for the weather Monday
night through Thursday across the Ohio Valley and lower Great Lakes
region. This weekend's upper low will will be centered near the Gulf
Coast by Monday night and Tuesday with a weak upper trough remaining
across the region. Sufficient moisture will also remain across the
area with mean rh from 850 to 700 mb at 65 to 75 percent. Models
point to possibly a bit drier northwest Wednesday. Otherwise will
have chance pops everywhere bumping into likely far east where best
moisture will be. Thursday models show a cold front in the area
although moisture will be less. Will still hang onto a low chance
however with the surface boundary in place. Highs in the mid 80s
Thursday and 80 to 85 Wednesday and Thursday.


.AVIATION /18Z Thursday THROUGH Tuesday/...
VFR conditions will continue through the overnight. Clouds will
gradually thicken and lower overnight ahead of approaching low
pressure system.

OUTLOOK...Non-VFR possible Friday afternoon through Sunday with
showers and thunderstorms.


Winds will be increasing with time beginning tonight and shift
around to a southerly direction by Tomorrow morning ahead of the
next low pressure system that will settle in over the Great Lakes.
Winds will remain south to southeasterly through Saturday evening
and then begin to diminish by late Saturday night. As the low
pressure system shifts south into the Ohio Valley region Sunday
night, flow will shift around to an easterly direction and become
light and variable for Monday.

Due to upper level low pressure and cooler air aloft there is the
potential for waterspouts Saturday afternoon/evening and again
Sunday. Will add mention of waterspouts for these time periods.




NEAR TERM...DJB/Greenawalt
SHORT TERM...Lombardy
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