Scientific Forecaster Discussion
fxus61 kcle 230110
Area forecast discussion
National Weather Service Cleveland Ohio
910 PM EDT Fri Jun 22 2018
slow moving low pressure across western Indiana will drift to
Western Lake Erie by Saturday morning, lifting a warm front north
towards the lake. The low will weaken and drift towards New England
Saturday into Sunday. High pressure will build southeast across the
Great Lakes Sunday into Tuesday.
Near term /through Saturday night/...
convection has died down significantly since sunset. Will
continue scattered showers overnight as low, currently into west
central Ohio, tracks northeast overnight. No other changes for
the 930 update.
vertically stacked low over western Indiana will slowly pivot
northeastward and weaken over Lake Erie by Saturday morning. Ongoing
convection associated with 300mb upper divergence and modest
instability over central Ohio, on the order of 500-750 j/kg MLCAPE,
will move northeast towards the Cleveland area over the next several
hours. This is the main wave of precipitation expected through 00z,
however some isolated showers/storms may develop across the region
during this time. Hi-res guidance has a decent handle on the ongoing
situation, which gradually weakens the convection around/after 00z,
as the upper divergence associated with the left exit region of the
upper jet moves northeast of the area and corridor of instability
stops advecting north-northeast. Guidance suggests a second wave of
convection, associated with the nose of a low level jet, secondary
upper divergence maxima and remaining Reservoir of instability, may
develop just southwest of the forecast area and moves northeast into
Northern Ohio from 00z to 03z before weakening. Pops are trended
towards these two waves of precip across the area. Main impact from
the convection is heavy rainfall, with modest instability,
long/skinny cape profile, weak deep layer shear, ample pwats and
warm cloud depths. Storm motions have been on the slower side, but
are generally progressing east northeast with storm training
somewhat limited at this point. However, if storms can line up and
train over a single spot, excessive rainfall and flooding cannot be
ruled out, with rainfall rates in excess of 2" per hour possible.
Convection in general will weaken overnight, with a good period of
dry conditions possible. Hi-res models hinting at some more
development on the nose of the low level jet across far northeast
Ohio and northwest PA around 09z-12z. Scattered showers and a storm
or two may pop up across the area Saturday afternoon/early evening
with the low spinning over Lake Erie, although instability will be
very marginal, with only a few hundred j/kg cape developing Saturday
afternoon. Have kept thunder mention confined to chance at this
point. Have pops generally ramping down across the area Saturday
night with the low moving out of the area. No big changes to
temperatures from previous forecast, with lows in the mid 60s
tonight and Saturday night and highs in the mid to upper 70s on
Short term /Sunday through Monday night/...
a secondary shortwave/trough will move through the region
mainly Sunday morning and will likely produce some lingering
showers especially over the eastern portion of the County Warning Area.
Improving conditions will gradually spread across the western
part of the area. High pressure will build across the region on
the surface and aloft by Monday morning and bring pleasant
conditions with lower humidity.
Fair weather will continue into early Tuesday as the ridge gradually
moves east of the region. A southeast return flow will develop in
the afternoon with warm advection. The isentropic lift may be
sufficient over Northwest Ohio in conjunction with a developing warm
front to produce some convection in the afternoon which may progress
across the region in the afternoon.
Long term /Tuesday through Friday/...
an upper level low will move north of the Great Lakes region
Tuesday night through Wednesday. This low will push a series of
surface systems across the forecast area. Showers and
thunderstorms will develop in the west Tuesday night and become
more widespread on Wednesday as a surface cold front moves
through the region. Both the European model (ecmwf) and GFS are fairly consistent
with this solution. High pressure will build into the area
Thursday into Friday. Temperatures will climb into the mid 80s
by the end of the week. A few scattered afternoon showers are
not of the question on Thursday or Friday but at this time
confidence is low. I will keep the mention of precipitation out
of the forecast for Thursday and Friday.
Aviation /00z Saturday through Wednesday/...
thunderstorms will begin to diminish with sunset. Scattered
showers will persist. Low pressure centered over ind will drift
NE and move across Northwest Ohio late tonight, lifting warmfront across
Northern Ohio. Expect IFR to become more widespread south of the
Outlook...non-VFR conditions likely Saturday into Sunday in
showers and thunderstorms.
easterly winds on the north of the slow moving low pressure area
over Indiana are strongest over the Lake West of the islands. The
winds and waves are sufficiently strong to warrant continuing the
Small Craft Advisory and beach hazard statement until the evening
update around 10 PM. As the low pressure approaches the lake...the
pressure gradient will weaken and allow the winds to relax and veer.
The low pressure will move toward the western edge of Lake Erie
around 12z Saturday and move to the eastern end of the lake by 12z
Sunday. A trough will linger west of the low across the lake Sunday
morning. High pressure will build south over the lake Sunday night
and Monday. The high will move east of the lake by Tuesday and a
southerly flow will develop. Low pressure will move across the upper
lakes on Wednesday and a stronger southwesterly flow will develop
and a Small Craft Advisory may be needed. High pressure will build into the region
for later in the week.