U.S. Severe Weather Forecast for Tomorrow
Upcoming severe weather outlook.
acus02 kwns 251723
Storm Prediction Center ac 251722
Day 2 convective outlook
National Weather Service Storm Prediction Center Norman OK
1222 PM CDT Friday Jul 25 2014
Valid 261200z - 271200z
..there is a slight risk of severe thunderstorms across parts of the middle MS
valely...southern Great Lakes and Northern Ohio valley...
Severe thunderstorms capable of producing damaging winds appear
likely across parts of the upper Midwest...Ohio Valley and southern
Great Lakes from Saturday afternoon into Saturday evening.
Marginally severe wind gusts and hail will also be possible across
much of Kansas into southern Nebraska and in Pennsylvania...southern
New York and New Jersey Saturday afternoon.
..mid MS valley/Northern Ohio valley/southern Great Lakes...
West to northwest middle-level flow will be in place Saturday from the
upper MS valley eastward into the Great Lakes and Ohio Valley. At the
surface...a cold front is forecast to move southeastward into the western Great Lakes
region and middle to upper MS valley by afternoon. A large warm sector
should exist from the middle-MO valley eastward into the southern Great Lakes
where surface dewpoints should be in the upper 60s to middle 70s f. As a
result...model forecasts develop moderate to strong instability
across the slight risk area during the day with storms initiating
ahead of the front in the middle-MO valley around midday. Convective
coverage is forecast to expand eastward across southern Iowa...northern MO...Illinois and
ind during the afternoon as a mesoscale convective system develops along the instability
axis. A persistent and organized line-segment may develop and move
eastward across the Northern Ohio valley during the late afternoon and early
NAM forecast soundings along the instability axis for Davenport Iowa
and Indianapolis ind at 21z/Sat show impressive thermodynamics with
MLCAPE above 2500 j/kg and very steep lapse rates. In addition...the
wind profile has directional shear below 850 mb with substantial
speed shear in the middle-levels resulting in 40 to 50 knots of 0-6 km
shear. This environment should be favorable for a severe producing
mesoscale convective system with widespread wind damage possible. If the lower to middle 70s f
dewpoints materialize across much of the slight risk area by
Saturday afternoon...then an upgrade to moderate risk across parts
of the middle MS valley and Northern Ohio valley may be necessary. Model
solutions still differ markedly on the magnitude of the severe
threat Saturday afternoon and uncertainty is still significant
concerning the day 2 forecast.
West to northwest flow will be in place across the central and northern
plains Saturday as a cold front moves southward through the Central Plains.
Ahead of the front...surface dewpoints should be in the middle to upper 60s
f resulting in the development of moderate instability by afternoon.
Thunderstorm initiation appears probable along the front by
middle-afternoon from southern Nebraska southward across much of Kansas. Forecast soundings
in central and western Kansas show MLCAPE above 2000 j/kg with about 30 knots of
0-6 km shear. This combined with very steep lapse rates and high
temperature-dewpoint spreads may be enough for marginally severe wind gusts
associated with high based storms.
A subtle shortwave trough is forecast to move across the central and
northern Appalachian Mountains during the day on Saturday. At the surface...winds
will be south southwesterly across much of the eastern Seaboard where a
corridor of low-level moisture will be in place. Surface dewpoints in
the middle to upper 60s f should result in the development of moderate
instability from Virginia extending northward into central and eastern PA. Although
subsidence may exist just behind the shortwave trough Saturday
afternoon...isolated thunderstorms may be able to initiate across
parts of the middle-Atlantic and central Appalachian Mountains as surface temperatures
peak in the afternoon. The moderate instability combined with steep
low-level lapse rates may be enough for marginally severe wind