746
FXUS63 KGRB 152325
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
625 PM CDT Tue Aug 15 2017

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Wednesday
Issued at 233 PM CDT Tue Aug 15 2017

The latest RAP analysis and satellite/radar imagery show high
pressure centered over Lake Superior and extending southward over
the Badger State.  Morning stratus has evolved into a cu field,
which remains most widespread over far northeast WI and also the
southern half of the state.  The next weather system resides
upstream over the north-central Plains, and is expected to gradually
push towards the region over the next 24 hours.  Precip chances
and trends with this system are the main forecast concerns.

Tonight...High pressure will be sliding east across the region
tonight.  Mid and high clouds will gradually be increasing through
the night, but do not look to lower until after midnight. Otherwise,
boundary layer winds look low enough for decoupling, which will lead
to patchy ground fog developing in the cold spots of northern WI.
Lows ranging from near 50 degrees in the north to near 60 degrees in
the south.

Wednesday...High pressure will slide to the eastern Great Lakes,
while the flow aloft will turn to the south and southwest.  Mid and
high clouds will continue to thicken and lower during the morning,
but dry air below 700mb should hold off precip for most of the area
except for possibly far north-central WI where some decaying showers
could sneak in from the west.  Moisture will be increasing from the
west during the afternoon, though the best moisture transport will
remain well west of north-central WI.  Additionally, elevated
instability and mid-level lapse rates also look rather poor.  So
will show a slight increase in precip chances over western areas
through the afternoon, but will leave thunder as isolated in nature.
Temps will be fairly similar to todays readings.

.LONG TERM...Wednesday Night Through Tuesday
Issued at 233 PM CDT Tue Aug 15 2017

First upper trough to move across the western Great Lakes region
is expected late Wednesday night into Thursday evening, with the
second system arriving Friday night into Saturday. Beyond Saturday,
500mb pattern should be fairly zonal over the United States into
early next week.

For the system Wednesday night into Thursday, latest model trends
suggests a slower arrival of the main precipitation band due to
slower arrival of system and overcoming dry air aloft. There may
be a brief period of showers early Wednesday evening across the
north with first area of showers. The main band of precipitation
is expected to arrive into the southern half of the forecast area
during the mid to late evening hours, then work into far northeast
Wisconsin after midnight. Showers and thunderstorms are expected
across the area, but the risk of severe weather is low. The
showers and thunderstorms should move east of the area Thursday
morning with additional scattered shower and thunderstorm activity
across northeast and east-central Wisconsin Thursday afternoon as
a cold front moves across the area. It is possible that a storm
could become strong or severe Thursday afternoon. Any showers will
come to an end Thursday evening.

A brief break in the rain can be expected Friday before the next
system approaches from the west. The next chance for rain will be
Friday night into Saturday. Dry conditions expected Sunday as weak
high pressure dominates the pattern. Low confidence in rain
chances next Monday and Tuesday due to uncertainty in timing of
systems through the mean flow.
&&

.AVIATION...for 00Z TAF Issuance
Issued at 625 PM CDT Tue Aug 15 2017

Pretty good night for flying, with mostly high clouds
around. Some patchy ground fog is possible around sunrise. Middle
clouds will increase Wednesday with a small chance of showers in
the afternoon west of a Land O`Lakes to Antigo to Waupaca line.
Showers and thunderstorms are likely Wednesday night and Thursday
as low pressure moves across the area.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM.....MPC
LONG TERM......Eckberg
AVIATION.......RDM