FXUS63 KGRB 231132

Area Forecast Discussion
National Weather Service Green Bay WI
632 AM CDT Thu May 23 2019

Updated aviation portion for 12Z TAF issuance

.SHORT TERM...Today...Tonight...and Friday
Issued at 320 AM CDT Thu May 23 2019

A jet streak moving across Upper Michigan and far northern Wisconsin
could produce scattered showers in the far north today. Otherwise
it will be a partly cloudy and seasonable day with gusty west winds.

Clouds will increase tonight as an upper trough approaches from
the northern Plains. Some light rain could move into central
Wisconsin towards daybreak in broad warm advection pattern.

Showers and elevated thunderstorms are likely Friday as a surface
warm front moves north across southern Wisconsin. Clouds, showers
and easterly winds from Lake Michigan should keep highs 3 to 8
degrees below normal. Rainfall looks to be modest, and should not
significantly effect river and stream levels.

.LONG TERM...Friday Night Through Wednesday
Issued at 320 AM CDT Thu May 23 2019

Forecast concerns generally revolve around potential for severe
storms on Friday evening, followed precipitation chances late in the
holiday weekend. The gfs/ecmwf remain in decent agreement so will
continue a blend of these model solutions.

Friday night through Saturday night...As low pressure lifts
northeast across the northern Plains, models continue to project a
warm front lifting northeast across Wisconsin on Friday evening. How
far north this warm front reaches remains uncertain due to the
potential of precip and southeast winds off Lake Michigan north of
the front. The latest indications suggest this warm front could
reach as far north as central and east-central WI on Friday evening.
Though a cold front will not be too far behind the warm front, this
raises the potential for a window of strong/severe storms on Friday
evening into the early overnight. Will have ample elevated moisture
transport, high precipitable water values, and wind shear of 40-50
kts during this time which would be supportive of strong convection.
If the warm front reaches central to east-central WI, some
indications of MU capes upwards of 1000 j/kg as well. Will keep a
mention of the possibility in the HWO. The chance of rain will exit
eastern WI late Friday night. Then the region will be the southern
periphery of shortwave energy moving across Lake Superior on
Saturday. A few showers look possible across far northern WI, but
the threat of storms appears low elsewhere as dewpoints mix out in
the afternoon. Low level temps are substantially warmer in the gfs
than the ecmwf, but a blend would suggest low 80s are possible
across much of eastern WI away of the Lake and Bay. High pressure
then builds in for Saturday night, which looks mostly clear and

Rest of the forecast...The high pressure system will provide one
more day of quiet weather on Sunday. The precip chances increase
again late Sunday night into Monday when low pressure travels just
west of the region, and return flow pushes a warm front north across
the state. Models have waffled a bit on timing this next chance of
precip, so some uncertainty remains. Regardless, high levels of
elevated moisture transport, instability aloft, and high pwats above
1.5 inches suggest a wet period is likely towards the end of the
holiday weekend. It is too early to assess the severe threat, but
the pattern looks favorable for severe weather over at least parts
of the area along with locally heavy rainfall. Precip chances will
carry into Tuesday until a cold front clears the area. The quieter
weather is anticipated for the middle of next week.

.AVIATION...for 12Z TAF Issuance
Issued at 631 AM CDT Thu May 23 2019

MVFR ceilings are expected today roughly west of a Marinette to
Wisconsin Dells line, with mostly VFR ceilings to the east. VFR
conditions are expected across the entire area this evening through
most of the night, though MVFR ceilings may return towards

A warm front approaching from the south will bring showers and
scattered thunderstorms Friday with MVFR visibilities and MVFR or
IFR ceilings along with the precipitation.




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