Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Cleveland Ohio
419 am EDT Sat Sep 20 2014
temperatures will warm today ahead of a low pressure system moving
through the upper Great Lakes. This system will push a strong cold
front across the area on Sunday. High pressure will build over the
Ohio Valley on Monday and expand over the Great Lakes region on
Near term /until 6 PM this evening/...
the forecast area will be located between high pressure along the
New England coast and low pressure moving into the upper Great
Lakes. A fair amount of diurnal clouds developed across West
Virginia and Pennsylvania on Friday and this moisture can be seen on
the 00z pbz sounding in the 850-700mb layer. This moisture is
forecast to spread into northeast Ohio with southerly flow with
partly to briefly mostly cloudy skies. Despite this cloud
cover...temperatures will be above normal with highs in the upper
70s for all but interior northwest PA. Even carrying 80 degrees in a few
western counties given breezy southerly winds in the 15-20 miles per hour
range. Winds will gust to 30 miles per hour at times in Northwest Ohio.
Moisture will also sneak into Northwest Ohio late in the day in the
warm sector ahead of the approaching cold front. The airmass will
require considerable moistening before precipitation begins and
model soundings still show a cap near 850mb in place at tol through
22z. Will keep probability of precipitation low in the 20-30 percent range for Bowling Green
to Toledo and hold off until tonight for precipitation elsewhere.
Short term /6 PM this evening through Tuesday night/...
we will be watching the evolution of upstream convection seen early
this morning across Wisconsin and Iowa. If vigorous convection is
ongoing this afternoon across Illinois and Indiana as shown on the
00z 4km Storm Prediction Center WRF-nmm run then moisture transport ahead of the front
may be disrupted. This could delay showers and thunderstorms across
Northwest Ohio but overall still expecting scattered-numerous showers and
thunderstorms to fill overnight as moisture advection continues
ahead of the strengthening upper level trough dropping down from the
north. Raised temperatures into the middle 60s on Saturday night.
The upper level trough will swing across Northern Ohio on Sunday forcing
a strong cold front east across the area. A 125 knot upper level jet
will round the base of the trough with the orientation becoming
neutral to weakly negative. This results in some interesting
differences between the models as the NAM is slower and stronger
with the surface low crossing Lake Erie on Sunday. The stronger and
slower low would allow for more of an opportunity for NE Ohio to
destabilize on Sunday afternoon before the cold front comes through.
Initially leaning towards the NAM which sometimes seems to do a
better job with amplification of the surface feature associated with
these highly dynamic systems. The Storm Prediction Center has placed
northeast Ohio in a see text with a 5 percent chance of severe
thunderstorms in NE Ohio and northwest PA on Sunday afternoon. Not
expecting much sun...but if temperatures can recover into the middle
70s then moderate instability will develop with strong shear and
upward momentum. Looks like frontal timing during the early
afternoon would place better chances for severe thunderstorms to our
east where they will align with peak heating but timing will
certainly be something to watch.
Cold air surges south across the lake on Sunday night with lake
effect showers increasing. This will be for a fairly short window as
the trough quickly pulls away to the east and very dry air
overspreads the lake. Highs on Monday will be cool and much of NE
Ohio/northwest PA will not make it out of the 50s. Northwest Ohio should be able to
reach the low 60s with more sun expected.
High pressure builds over the Ohio Valley on Monday with light winds
and good radiational cooling setting up...especially across our
southern counties. Mins generally expected in the low 40s but could
see a few of the cooler locations dip into the 30s. Heights aloft
rebound quickly on Tuesday and temperatures will warm 6-8 degrees
from mondays highs...even after a cool start to the day.
Long term /Wednesday through Friday/...
dry weather and near normal temperatures are forecast for this
period. A ridge will be in control of the weather. Used a blend of
guidance for the temperature forecast.
Aviation /06z Saturday through Wednesday/...
VFR through late afternoon. A warm front will cross the area
through daybreak with mainly cirrus. The pressure gradient will be
increasing today ahead of a cold front that will move through
Saturday night. With the winds slowly increasing overnight not
forecasting fog at the taf sites because of the
wind...however...patchy 5sm br is expected elsewhere through 9 am.
The models are all over the place in its location of low level
moisture. Some broken VFR ceilings near 4500 feet could develop by
early afternoon especially over NE Ohio and northwest PA. Confidence is
marginal the best chance for broken clouds will be just ahead of
the showers and thunderstorms that will be spreading in from the
northwest after 7 PM. Winds will be gusty ahead of the cold front.
Outlook...non-VFR conditions in showers and thunderstorms late Saturday
night and Sunday then non-VFR ceilings lingering over NE Ohio/northwest PA
for today the gradient and winds will be increasing ahead of a cold
front that will move across the lake tonight. As the winds increase
low level warm air will be moving in especially this afternoon and
that may help keep the winds from getting out of control on the
lake. At this time leaning toward 15 to 20 knots except on the
extreme east end where the winds will be 20 to 25 knots and the
southwest flow could cause waves approaching 3 to 5 feet. Will have
a Small Craft Advisory for that area through 9 PM.
Otherwise southwest winds 10 to 20 knots tonight and then increasing
winds from the west after frontal passage late Sunday into Sunday
night when a Small Craft Advisory will likely be needed. After that
high pressure will be building into the Ohio Valley and that will
keep the winds westerly on the lake Monday night into Tuesday
evening. Will have to keep an eye on the wind speeds mainly on the
east end of the lake as the waves will be choppy.
For Wednesday through Friday a ridge will build in from the
northeast and that will mean and east or southeast flow. At this
time the winds seem light enough that it will not prompt the need
for a Small Craft Advisory.
Special marine warnings for thunderstorms may be needed on the lake
this evening through Sunday. Mariners will need to be cautious as
some of the storms will be strong.
Marine...Small Craft Advisory until 9 PM EDT this evening for lez148-