Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 190345
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1045 PM CDT WED MAY 18 2016

Updated aviation portion for 06Z TAF issuance

.SHORT TERM...Tonight and Thursday
Issued at 216 PM CDT Wed May 18 2016

Dry air mass aloft will preclude any precipitation in the
forecast over the next 24 hours. Therefore, the main focus to be
on potential for frost tonight and how low to take relative
humidity levels Thursday afternoon.

The 19z MSAS surface analysis indicated a ridge of high pressure
stretched from the Central Plains NE through the Western Great
Lakes into SW Quebec. Spotty fair weather cu field had popped up
in the daytime heating, but no precipitation was noted on radar.
Current temperatures were approaching normal readings for mid-May
with favorable mixing bringing very dry air down to the surface
(as noted by the relative humidity in the 20-30 percent range).

This surface ridge axis to gradually slip just to our east tonight
and eventually allow boundary layer winds to increase from the
west to around 10 knots by daybreak. Combination of light surface
winds and dry air mass will still allow temperatures to quickly
cool this evening and again bring a threat for frost to parts of
NE WI. 925 mb temperatures are expected to rise from +6 to +8C
this morning, to +10 to +11C by 12z Thursday. Therefore,
temperatures will not be as cool as the previous two nights. Look
for mins to range from the lower to middle 30s North-Central WI,
upper 30s to around 40 degrees south. After collaboration with ARX
and DLH, will issue a frost advisory for Northern and parts of
Central WI from 07z-12z Thursday.

Both the surface and 8H ridge axes appear to be far enough to the
east on Thursday to allow winds to become S-SW and bring warmer,
more moist air into WI. Models/time sections show an increase in
low-level moisture along with higher clouds passing overhead. The
end result will be more cumulus formation and a partly cloudy sky
versus mostly sunny. Lakeshore areas should see more sun and
cooler conditions as the lake breeze works inland during the late
morning/afternoon. Max temperatures will reach the lower to middle
60s near Lake MI, mainly upper 60s to lower 70s elsewhere.

.LONG TERM...Thursday Night Through Wednesday
Issued at 216 PM CDT Wed May 18 2016

Temperatures through the period, and pcpn trends early next
week, will be the main fcst concerns.

Surface high pressure will reside over the western Great Lakes at
the beginning of the period, and is expected to remain through
the weekend. A weak upper level trough will pass through the
region on Friday and Friday night, but will likely be unable to
produce anything more than virga in a stable and very dry air
mass. after the upper trough moves through, a high-amplitude
upper ridge will build over WI for the weekend. This will keep the
prevailing dry conditions in place. Temperatures will be near
normal at the beginning of the period, and warm to above normal
over the weekend, with the typical warm spots potentially reaching
80 by Sunday.

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. Although details are sketchy this far out, it appears that
the best pcpn chances will occur on Wednesday, as a sfc low lifts
northeast into WI, coincident with the passage of a short-wave
trof.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1045 PM CDT Wed May 18 2016

VFR conditions expected to prevail over the next 24 hours as a
ridge of high pressure is forecast to reside over the Great Lakes
region. Daytime cu field with bases at 6-8K ft will develop again
on Thursday. Winds to remain light and variable through tonight,
then become more S-SW on Thursday as the ridge slips a bit farther
east, becoming light and variable again Thursday evening.
Exception to these winds will be at MTW where lake breeze would
shift the winds to the SE.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Frost Advisory from 2 AM to 7 AM CDT Thursday FOR WIZ005-010>013-
018-019-021-030-035-036-045.
&&

$$

SHORT TERM.....Kallas
LONG TERM......Kieckbusch
AVIATION.......Kurimski



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