Scientific Forecaster Discussion
fxus61 kcle 181435
Area forecast discussion
National Weather Service Cleveland Ohio
935 am EST Thu Jan 18 2018
high pressure over the Ohio Valley today will settle towards the
southeastern states through Saturday. Ridging aloft will expand over
the lower Great Lakes on Sunday in advance of a trough approaching
from the plains. The associated low pressure system will track
northeast through the upper Midwest on Monday and central Great
Lakes on Tuesday.
Near term /through Friday/...
update...only minor changes to hourly temperatures this morning
as the observations were running a bit cooler than forecast.
Otherwise...forecast looks right on track.
Previous discussion...mid and high clouds seen on satellite
imagery over Wisconsin this morning will brush northern portions
of the area this afternoon/evening. The majority of the day
will be sunny and made minor adjustments to the cloud grids to
ensure mostly sunny wording outside of northwest PA.
A gradual warming trend will continue through the near term with
continued southwest flow over the region between high pressure over
the Ohio Valley and low pressure and a series of troughs passing
north of the Great Lakes. The airmass overhead is dry with lots of
sunshine expected over the next 2 days. High clouds will brush
the area at times with sct-bkn lower clouds possible in northwest PA
today and tonight as a weak trough slides across Eastern Lake
Erie. A large spread exists between the guidance for
temperatures with the met running around 5 degrees warmer than
the mav for today and tomorrow. The met has been performing
poorly and will side towards the cooler mav numbers after a cool
start to the day. A very strong inversion is developing as the
airmass warms overhead with limited mixing depth. Despite this,
highs will climb another 7-10 degrees both today and Friday,
pushing most locations above the freezing mark by Friday
afternoon. Southwest winds will be brisk with speeds of 10-15
mph and frequent gusts to 20 mph or higher, making the warming
trend feel a little slower than it is.
Short term /Friday night through Sunday night/...
high pressure centered over the southeastern US will build
northeastward, with continued return flow/warm air advection through the Ohio
Valley into the Great Lakes over the weekend. Temperatures will warm
into the upper 30s/low 40s on Saturday across the area, and into the
mid 40s on Sunday. Dry conditions are expected through the day on
Saturday, with light rain developing across the area late Saturday
night through Sunday night as isentropic ascent increases through
the region. Any precip should remain fairly light, with the onset
later into the overnight across most of the area as fairly dry 925-
800mb layer saturates. Better precip chances will arrive late Sunday
night as a cold front approaches the area from the west.
Long term /Monday through Wednesday/...
main focus of the long term period is the cold front passage
Monday/Monday night. Deepening low pressure across the western Great
Lakes will force a cold front eastward across the area. Minor timing
differences between the GFS and the European model (ecmwf)/Gem lead to a bit lower
confidence in pops, temps Monday and Monday night and precip type
changeover behind the front. The 00z GFS remains fairly fast with
the fropa, bringing the front through the area by Monday evening,
while the European model (ecmwf)/Gem remain slower, not exiting the area to the east
until late Monday night into early Tuesday morning. Precip onset and
timing of changeover from rain to snow remain a bit uncertain, so
have tried to reflect a compromise of the two solutions in the
forecast. Given the uncertainty with the timing, have elected for
high likely pops in lieu of categorical at this time. Have trended a
bit slower with the changeover to snow as well, and a bit warmer
Monday, especially across the eastern half of the forecast area. A
return to more normal temperatures is expected Tuesday through
Wednesday behind the front, with highs in the low to mid 30s each
day. The best chance for precip behind the front is Tuesday, as the
backside of the upper low swings east through the Great Lakes. Have
opted for chance pops at this point Tuesday into Tuesday night, with
possible lingering lake effect/lake enhancement across the snow belt
Wednesday, as another trough swings east through the Great Lakes.
Aviation /12z Thursday through Monday/...
southwest winds be breezy today with gusts to 20-25 knots as
the area lies between low pressure across the northern Great
Lakes and high pressure over the Ohio Valley. A low level jet
will develop this evening with winds near 2000k feet increasing
to 40-50 knots. Added a mention of low level wind sheer to most
of the terminals overnight. Otherwise skies will be mostly clear
with VFR conditions expected with the only exception being at
eri where MVFR clouds are possible near Lake Erie.
Outlook...non-VFR possible Saturday afternoon into Sunday then
again Monday in rain showers.
southwest flow on the lake will continue for the remainder of the
week into the weekend as high pressure remains centered across the
southeast US. Winds will generally remain in the 15 to 20 kt range
through Friday. Winds will increase a bit Friday night into Saturday
as low pressure passes through the northern lakes, but will decrease
through the remainder of the weekend becoming, more southerly on
Sunday. Southerly winds will increase again on Monday into Monday
night as a cold front moves east across the lake, becoming southwest