Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 241705
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1205 PM CDT WED AUG 24 2016

Updated aviation portion for 18Z TAF issuance

.SYNOPSIS...
Issued at 342 AM CDT Wed Aug 24 2016

Scattered showers and thunderstorms today, then a couple days of
quiet weather.

An upper anticyclone within the subtropical ridge will gradually
shift from the Gulf Coast to the Mid-Atlantic region during the
forecast period. At the same time, near full latitude ridging over
the eastern Pacific will slowly drift westward. A positively
tilted trough will remain between the ridges and extend from the
Hudson Bay region to the West Coast for the first half of the
period, before weakening away later in the period.

Temperatures will remain modestly above normal for the next couple
days, drop back to near or a little below normal for the end of
the work week and the start of the upcoming weekend, then return
to a little above normal for early next week. After today, there
appears to be one substantial opportunity for precipitation. That
will come with a wave crossing the area this weekend. That system
seems sufficient to result in near normal amounts for the period
(which is about 3/4 inch for a week at this time of year). But the
convective nature of the precipitation will likely result in
considerable variability across the area.
&&

.SHORT TERM...Today...Tonight...and Thursday
Issued at 342 AM CDT Wed Aug 24 2016

A large cluster of convection supported by shortwave is crossing
the area this morning. The shortwave will shift off to the east
early today. So the main forecast issues are how long to linger
high PoPs this morning, and the potential for re-development this
afternoon. The former was an issuance time decision based on radar
trends, and will probably need some additional adjustment shortly.
As far as the latter is concerned, the atmosphere will be
overturned by this mornings storms and there will be lingering
cloud cover. Large scale subsidence will also work against
redevelopment. On the other hand, surface boundary is still way to
the west and will cross the area during the afternoon. Expect some
redevelopment, but with limited coverage due to previously
mentioned factors and westerly flow above the surface limiting
convergence near the boundary. Lingered isolated-scattered
category PoPs into the evening, especially in the east.

Models suggest precipitation will expand to our south overnight as
lift in RRQ of upper speed max shifts through the region. The
ECMWF and GFS actually brush precipitation through the far
southern portion of the forecast area around daybreak. Opted to
linger low PoPs over the southeast portion of the area through the
night, but kept Thursday dry for now. The day shift will need to
re-assess that.

Deep westerly flow on Thursday should still allow temperatures to
warm to above normal levels, with cooling aloft steepening lapse
rates and probably resulting in some gusty winds. Dew points will
also be dropping during the day as drier air settles into the
region.

.LONG TERM...Thursday Night Through Tuesday
Issued at 342 AM CDT Wed Aug 24 2016

Main concern for this period will be the chances of showers and
thunderstorms over the weekend. For Friday, a weak disturbance
and surface boundary will bring a chance of showers across Upper
Michigan which may clip our far northeast counties. Added a
chance of showers for this period across the far northeast. High
pressure will then dominate the weather pattern through most of
Friday night. Latest ECMWF model has trended faster, thus day
shift may need to add a small chance towards sunrise.

Low pressure will move across the region over the weekend. This
system will bring showers and thunderstorms to the area. Locally
heavy rain is possible at times Saturday and Saturday night. weak
high pressure will build into the region early next week. There
is a small chance of storms Monday and Tuesday, but most of this
period will be dry. Only minor changes made to the temperatures.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1204 PM CDT Wed Aug 24 2016

A cold front crossing the MN/WI border will push across the region
late this afternoon into this evening.  Should see a slow
improvement in the ceilings this afternoon ahead of the front,
especially over northern WI where IFR conditions are hanging tough.
Elsewhere, mainly vfr cigs will prevail, but with the possibility of
isolated showers and storms developing through the end of the
evening. Behind the front, the low clouds will clear, leaving only
sct to broken high clouds through the rest of the taf period.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Beach Hazards Statement until 10 PM CDT this evening FOR WIZ022-
040-050.
&&

$$

SYNOPSIS.......Skowronski
SHORT TERM.....Skowronski
LONG TERM......Eckberg
AVIATION.......MPC



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