Scientific Forecaster Discussion
fxus61 Kiln 300727
Area forecast discussion
National Weather Service Wilmington Ohio
327 am EDT Tue may 30 2017
weak surface ridging should keep conditions dry today. An upper
level disturbance along with a cold weak front will bring a
chance of precipitation tonight and Wednesday as they move
across the Great Lakes and Ohio Valley. High pressure will then
build into the area for Wednesday night.
Near term /until 6 PM this evening/...
the center of an upper level closed low across Ontario will
meander/rotate north today. For our region, a weak cold
front/surface trof axis will move east of the County warning forecast area by mid
morning. We should then see weak surface ridging. As a result,
mid clouds this morning will give way to few-scattered high based
cumulus development in the afternoon. It will be slightly cooler
than yesterdays readings, ranging from the mid to the upper 70s
for most locations, with perhaps an 80 in the far southeast.
Short term /6 PM this evening through 6 PM Wednesday/...
the center of the upper level closed low will elongate and
shift east tonight through Wednesday. As this occurs, an
embedded disturbance rotating around the base of this low will
propagate across the region. This feature will team up with
another weak cold front to bring a chance of showers tonight,
and a chance of showers and thunderstorms on Wednesday. The
front should clear our eastern zones by Wednesday evening,
allowing surface high pressure to build in from the west. After
lows in the mid 50s, highs on Wednesday will be slightly cooler
again, ranging from the lower to mid 70s.
Long term /Wednesday night through Monday/...
with the cold front moving clear of the area on Wednesday
evening, precipitation chances will come to an end, as a
relatively dry area of surface high pressure moves into the
area. With large-scale troughing over the eastern half of the
conus, upper flow will remain out of the WNW, keeping the air
mass relatively cool and dry (even though the clear skies will
allow surface temperatures to reach values near normal on
thursday). With more unsettled conditions in the coming days,
Thursday clearly looks like the most tranquil weather day of the
As the surface high moves east on Thursday night, low level flow
will back to the southwest, allowing for warm frontal progression to
occur. As this developing temperature boundary ends up somewhat
parallel to the west-northwest flow aloft, attention will turn to any potential
shortwaves or jet streaks in the flow, which may help to spark
convection atop the increasingly favorable boundary layer
conditions. Unfortunately, specifics remain tough to pick out in the
models, with a lack of agreement in placement and timing for the
eventual convective episodes. Thus, will simply ramp pops up into
the 40-50 percent range through the day Friday, and allow for likely
pops in the southern half of the County Warning Area on Saturday. In what should be
a typical late Spring scenario with stronger shear to the north and
stronger instability to the southwest, a conditional threat for some
severe weather could exist in this time frame.
There are even wider differences in how the European model (ecmwf)/GFS runs have been
handling surface high/low development on Sunday and beyond, making
this a low confidence forecast for the second half of the weekend.
Overall trends do suggest lower precipitation chances on Monday and
The increase in southerly flow should allow for at least a temporary
increase in temperatures for Friday, but convective development (or
lack of development) will largely influence temperature forecasts
from that point forward. This forecast will indicate a very gradual
cooling trend through the rest of the extended period, but with
temperatures remaining within ~5 degrees of normal.
Aviation /07z Tuesday through Saturday/...
an upper level closed low just north of Lake Superior this
morning will continue to meander/rotate slowly north across
Ontario through the taf forecast period.
For today, a weak cold front/surface trof axis will move east
across the terminals through 12z. A few showers/isolated
thunderstorms will accompany this boundary, but should stay
mainly north of the terminals. Mid level clouds will scatter by
12z with winds veering from southwest to west.
For later this morning into this afternoon, our forecast area
should be in between weak weather systems. West winds will
increase between 10 and 15 knots by 16z with gusts between 18
and 22 knots. Few-scattered high based cumulus clouds beginning
around 6000 feet will lift to around 8000 feet by late
For this evening, few-scattered altocumulus can be expected with winds
diminishing toward 00z.
A weak disturbance approaching the region from the west may
bring clouds and a few showers near or after 06z Wednesday.
Outlook...thunderstorms will be possible on Friday.