Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 162301

Area Forecast Discussion
National Weather Service Green Bay WI
601 PM CDT Sun Jul 16 2017

Updated aviation portion for 00Z TAF issuance

Issued at 228 PM CDT Sun Jul 16 2017

Quiet weather through Monday, then more humid with thunderstorms
returning mid-week.

The westerlies across southern Canada and the northern CONUS will
deamplify and become progressive the next few days. Agreement
among the medium range models begins to break down after that,
but the pattern will probably trend back to one with a ridge in
the west and a trough in the east, though perhaps with less
amplitude than we`ve seen recently.

The period will begin with seasonably cool air and low humidities,
but warmer and more humid conditions will return fairly quickly.
Once in place, those conditions are likely to linger for the rest
of the period, albeit with some day to day variation.
As typical for this time of year, precipitation totals will
depend on the movement of individual convective systems. But the
overall pattern looks to support enough opportunities for
precipitation to result in above normal amounts for the period.

.SHORT TERM...Tonight and Monday
Issued at 228 PM CDT Sun Jul 16 2017

The latest RAP analysis and satellite/radar imagery show high
pressure centered over Lake Superior early this afternoon.  Very dry
air is associated with the high, with pwats falling to 0.5 inches.
As a result, skies have been gradually clearing from north to south
today, though scattered to broken ceilings are hanging on over
central and east-central WI.  There too, skies should turn mostly
clear by the end of the afternoon.  As high pressure slides south
into the area, temps and fog potential are the main forecast

Quiet weather is expected over the next 24 hours, thanks to high
pressure building southward across the central Great Lakes.  Very
dry mid-level air beneath the ridge axis will accompany the high,
leading to mostly clear conditions over the period.  As winds fall
off tonight, some potential for ground fog formation after midnight
due to min temps projected to fall below the cross-over temp.
Statistical guidance is not bullish on fog potential, so kept the
patchy wording over the sandy soil areas, like the previous forecast
showed.  Cool lows tonight ranging from the mid 40s to mid 50s.
Highs will be several degrees warmer than todays readings, and range
from the mid to upper 70s.

.LONG TERM...Monday Night Through Sunday
Issued at 228 PM CDT Sun Jul 16 2017

Though models differ on the details, there is likely to be a
round of convection as a frontal boundary crosses the area sometime
around Tuesday night. That will probably be followed by a lull in
the rain chances, though by then the models were sufficiently
different that the blend of guidance used to initialize the
forecast ended up with chance/slight chance PoPs for at least a
portion of the area. Additional rain chances will occur during the
remainder of the forecast as shortwaves in the flat upper flow
interact with the frontal zone to our south. The front appears to
be far enough south so that the heaviest rain and greatest
flooding potential will remain south of the area, but that will
certainly need to be watched closely in the coming days.

No significant chances were made the forecast initialization
generated from a broad-based blend of guidance products.

.AVIATION...for 00Z TAF Issuance
Issued at 601 PM CDT Sun Jul 16 2017

Mostly clear skies and light winds have settled in across the TAF
sites as high pressure builds in across the region. These
conditions are expected to last through Monday. The one main issue
could be ground fog formation late tonight into early Monday
morning. MOS guidance does not support much in the way of fog,
therefore will maintain the patchy mention of fog over the sandy
soil areas of northern Wisconsin with this issuance.

Issued at 228 PM CDT Sun Jul 16 2017

Winds and waves are both marginal for the small craft advisory
this afternoon. With a few gusts still occurring above 20 kts and
Minneapolis Shoal light around 25 kts, will keep the advisory and
beach hazard statement going into the evening. Most gusts should
remain at least into the 15-20 kts range through midnight.

Beach Hazards Statement until 10 PM CDT this evening for WIZ050.


LONG TERM......Skowronski
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