Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 202314
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
614 PM CDT FRI MAY 20 2016

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Saturday
Issued at 255 PM CDT Fri May 20 2016

Main forecast challenge to remain on temperatures as high
pressure to remain parked over the Great Lakes into the weekend.

The 19z MSAS surface analysis showed and area of high pressure
extended from the Upper MS Valley ewd through the Great Lakes to
upstate NY. A weak frontal boundary was situated well to our north
across Central Ontario. Despite the high pressure overhead,
visible satellite imagery indicated a decent amount of clouds
across the middle of the CONUS. Other than the fair weather
cumulus, most of the other mid/high clouds were associated with a
pair of fairly weak mid-level shortwave troughs.

Models continue to advertise the NE movement of one of these
shortwave troughs from the Mid-MS Valley into the Ohio River
Valley tonight. Any lift or forcing from this system will remain
to our south and east, thus dry conditions to hold over NE WI.
The only noticeable effect to us will be a wind shift to the N-NW
later tonight. Under mostly clear to partly cloudy skies with
slowly moderating temperatures aloft, anticipate min temperatures
to be a couple of degrees milder than last night. This would send
readings down into the upper 30s to around 40 degrees north, lower
to middle 40s south.

The mean flow becomes highly-amplified this weekend with a broad
upper trough over the Western CONUS, an upper ridge over the
Central CONUS and another upper trough over the Eastern CONUS. On
Saturday, NE WI to reside under a NW flow aloft which typically
signifies cooler weather. However, 8H temperatures are forecast to
be around +11C and the air mass over WI is still somewhat dry (dew
points in the upper 30s to middle 40s), so temperatures at the
surface are still expected to rise to above normal levels. Some
models continue to try and generate light showers Saturday
afternoon, but have continued to ignore this trend due to the
drier air mass in place than these models suggest. Look for partly
cloudy skies with max temperatures ranging from the upper 60s near
Lake MI, to the upper 70s over sandy soil areas from Wautoma to
Iron Mountain.

.LONG TERM...Saturday Night Through Friday
Issued at 255 PM CDT Fri May 20 2016

Temperatures through the period, dry conditions and elevated
fire danger over northern WI through Monday, and pcpn trends for
the next work week, will be the main fcst concerns.

Surface high pressure will reside over the western Great Lakes
through the weekend, and a high-amplitude upper ridge will build
over WI Sat ngt into Sunday. This will keep the prevailing dry
conditions in place. Temperatures will gradually warm through the
weekend, with highs in the upper 70s to lower 80s on Sunday. Lake
breezes will keep lakeshore communities in the 60s or lower 70s.

As the sfc high and upper level ridge edge east early next week,
return flow and increasing instability will bring a chance of
thunderstorms. Most locations should not see any pcpn until
Monday night, though sct thunderstorms may affect parts of
central and north central WI late Monday afternoon. The storms
should be focused along a weakening frontal boundary as it shifts
east through the forecast area Monday night into Tuesday. the GFS
is advertising a brief break in the pcpn late Tues ngt into Wed,
but the ECMWF keeps pcpn around the area. Low pressure is
expected to lift northeast through the western Great Lakes
sometime in the Wed to Thu period, but models differ on the
timing and track. Given the lack of agreement with the models,
will continue to carry chance pops for thunderstorms through
Friday.
&&

.AVIATION...for 00Z TAF Issuance
Issued at 614 PM CDT Fri May 20 2016

vfr conditions to continue through at least sunday with scattered
high based cumulus clouds during the afternoon and light surface
winds. &&

.FIRE WEATHER...
Issued at 255 PM CDT Fri May 20 2016

Deep mixing will cause dew points and relative humidity to drop
off Sat/Sun afternoon, with min RH in the 20s to lower 30s percent
range. Humidity will rise slightly on Monday, but still be in the
25 to 35 percent range over northeast WI. South winds will
increase, with gusts reaching 20 to 25 mph across most of the area
Monday afternoon. Parts of central and northern WI are still
experiencing high fire danger, and the continued dry weather, low
low RH and increasing winds on Monday will be cause for concern.
&&

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

$$

SHORT TERM.....Kallas
LONG TERM......Kieckbusch
AVIATION.......RDM
FIRE WEATHER...Kieckbusch



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