Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 251750
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1250 PM CDT Wed Apr 25 2018

Updated aviation portion for 18Z TAF issuance

.SHORT TERM...Today...Tonight...and Thursday
Issued at 327 AM CDT Wed Apr 25 2018

A short-wave trof exited eastern WI early this morning,
taking any light rain with it. Subsidence in the wake of the
disturbance resulted in a rapid decrease in cloud cover.
Satellite and surface observations indicated that the patchy fog
and low clouds that developed earlier over north central WI had
dissipated.

Under sunny skies, deep mixing through about 800 mb should
support highs in the 55 to 60 range today, except upper 40s and
lower 50 near Lake Michigan. Clear skies and light winds will
allow temperatures to settle into the middle 20s to middle 30s
tonight.

On Thursday, morning sunshine will give way to increasing clouds
as a cold front arrives in the afternoon. Post-frontal shower
activity is expected for areas northwest of the Fox Valley and
lakeshore areas in the afternoon, aided by the approach of a
short-wave trof. Mild highs in the middle 50s to middle 60s are
anticipated, with some cooling due to the front and rain during
the mid to late afternoon.

.LONG TERM...Thursday Night Through Tuesday
Issued at 327 AM CDT Wed Apr 25 2018

At the start of the period, a deep upper trough was noted across
the western Great Lakes region on Friday. A strong upper level
disturbance will drop southeast out of Canada Friday morning. This
system will move across the area Friday afternoon, bringing the
chances of showers and perhaps a few thunderstorms. Mid level
lapse rates were around 6.5 C/KM. What caught my attention tonight
was that the tops on the showers and storms would approach 12,000
feet which also supported the possibility of thunder. In addition,
bufkit soundings indicated very low wet bulb zero heights around
six thousand feet and an inverted-v structure that could bring
winds down from the mid levels, probably in the 30 to 40 mph range
in the stronger showers and storms. Enough confidence to add this
scenario into the Hazardous Weather Outlook (HWO). There may be a
few lingering showers across northeast Wisconsin Friday evening.

A major pattern shift is expected over the weekend into early
next week. Northwest flow aloft will shift to a southwest flow
pattern as an upper trough closes off across the southwest United
States. This pattern change will result in some of the warmest
temperatures of the year early next week along with the chances
for showers and thunderstorms. The details on rain chances are
murky at the moment, but did add thunderstorms to the forecast on
Tuesday. This system will need to be watched over the next
severals days to see if the risk for heavy rain increases. Along
with the warmer temperatures, marine fog may pose a risk along the
Lake Michigan shoreline at some point early next week. Only minor
changes made to max/min temperatures on a few days during the
period.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1250 PM CDT Wed Apr 25 2018

Clear skies and light winds are expected through
midday Thursday. An approaching cold front will bring the chance
of showers and MVFR conditions Thursday afternoon and evening.
&&

.HYDROLOGY...
Issued at 327 AM CDT Wed Apr 25 2018

Most rivers across the area are approaching crest or have crested
already. Minor flooding is occurring on the Oconto River near
Oconto and on the Wolf River Basin. Based on the latest river
forecasts, the Oconto River is expected to fall below flood stage
later today. On the Wolf River, minor flooding is expected to
continue into the middle of next week at Shiocton. At New London,
the Wolf River is expected to crest over the weekend right around
flood stage. On the little Wolf River at Royalton, the crest is
expected to occur right around flood stage on Thursday, then
slowly fall into the weekend. There is a chance of showers and
storms on Friday, but precipitation amounts are expected to be on
the light side. The risk for heavier rains return early next week
as the area is expected to see some of the warmest temperatures of
the year. There is still a lot of uncertainty on rainfall amounts
early next week.
&&

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

$$

SHORT TERM.....Kieckbusch
LONG TERM......Eckberg
AVIATION.......RDM
HYDROLOGY......Eckberg


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