Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 261559
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1059 AM CDT Sun Mar 26 2017

Updated aviation portion for 18Z TAF issuance

.SYNOPSIS...
Issued at 402 AM CDT Sun Mar 26 2017

Chilly and damp with occasional rain and drizzle today, then a
little warmer for the upcoming work week.

Split flow will continue across North America throughout the
7 day forecast period. A series of upper level cyclones embedded
within the southern stream will slowly cross the country. The
lead system will continue to bring clouds and periods of light
precipitation to the area today. The northward extend of
precipitation with subsequent systems has come into doubt as model
solutions now diverge on the storm tracks. Amounts will probably
be above normal across the southern part of the forecast area
which will be closer to the southern stream storm track, with
amounts across the north more uncertain. Clouds, precipitation,
and northeast winds will keep temperatures cool again today.
Readings should warm a little during the upcoming work week, but
are still likely to be cool on any days with widespread
precipitation.
&&

.SHORT TERM...Today...Tonight...and Monday
Issued at 402 AM CDT Sun Mar 26 2017

Adding detail to the precipitation forecast becomes increasingly
difficult with time. In the big picture, remnants of weakening
upper low will head northeast toward Lake Michigan today. We now
are in a situation where the atmosphere is very moist but forcing
rather weak. So will probably end up with small clusters of
showers and areas of drizzle today into tonight. But the timing
and location of those will be impossible to pin down, other than
the fact that the showers will probably be more numerous in the
east. Structured forecast with gradually decreasing PoPs this
afternoon into tonight. Temperatures will still be marginally
cold enough for some additional icing across the far northeast
early today, so will allow the advisory to run to its scheduled
expiration.

A weak mid-level shortwave will cross the area Monday. That should
be sufficient to kick off some showers, though coverage will be
limited. Twenty to thirty percent PoPs seemed sufficient for now,
especially since the normally reliable ECMWF is on the drier side
of the models in terms of precipitation coverage and QPF.

For max and min temps, leaned toward 3-hourly temps taken from a
blend of the recent top performing guidance products. That seems
to work well when there is a lot of low-level moisture and
cloudiness.

.LONG TERM...Monday Night Through Saturday
Issued at 402 AM CDT Sun Mar 26 2017

A period of drier weather is in store for the forecast area as
the surface low that is currently moving into the region departs
and the next low passes farther to the south. There are still
some slight chance PoPs for most locations on Monday night since
the 00Z GFS kept QPF in through 06Z Tuesday while the NAM held
onto it through 12Z. The 00Z Canadian had patchy QPF during the
night, but the ECMWF was dry except for far eastern Manitowoc
County through 06Z. This was all in advance of a 500 mb trough
axis and in the right exit region of an upper jet streak.

After that, surface high pressure and a 500 mb ridge are expected
to help keep the area dry Tuesday through Wednesday evening.
Models differ in their handling of a system that is forecast to
develop in the southwest CONUS. The GFS looks like the outlier as
it takes the system pretty much straight east to the Atlantic,
keeping any associated precipitation south of the
Wisconsin/Illinois border. The Canadian and ECMWF had some timing
and track differences but both had QPF across at least part of the
area starting Wednesday night, so PoPs return after 06Z Thursday.
There is a chance for snow and/or rain late Wednesday night in
parts of central and north central Wisconsin, then any
precipitation should change to rain during the day on Thursday as
chance PoPs spread across most of the area. There is a chance for
rain across the entire area by Thursday evening, with a change to
all snow during the night. Chance PoPs continue on Friday, with a
change to all rain as temperatures warm. Expect precipitation to
change to a mix or snow as it exits the area by 12Z Saturday.

Temperatures should be above normal through the period, with
highs mainly in the middle 40s to lower 50s, and lows in the 20s
to middle 30s.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1049 AM CDT Sun Mar 26 2017

Expect IFR/LIFR clouds/vsbys to persist with periods of rain and
drizzle through tonight. Guidance visibilities may be too low
today, but expect fog to take visbilities down tonight as surface
winds slacken off. Some improvements to visibilities and ceilings
are expected on Monday morning.


&&

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

$$

SYNOPSIS.......Skowronski
SHORT TERM.....Skowronski
LONG TERM......MG
AVIATION.......MPC



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