Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 171633
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1033 AM CST Fri Feb 17 2017

Updated aviation portion for 18Z TAF issuance

.SYNOPSIS...
Issued at 333 AM CST Fri Feb 17 2017

Above normal temperatures expected through the middle of next
week.

The upper flow across North America will remain split throughout
the forecast period, with the forecast area dominated by the
northern branch of the split. The southern stream will likely
begin to strengthen and expand northward next week. That may lead
to a significant cyclone over the middle section of the country
late in the week, with the system not reaching the forecast area
until after the end of the period.

The forecast area will be under the influence of mild air masses
from the Pacific that have downsloped the Rockies to get here. The
result will be above normal temperatures through most of the
period, with a bit of a cool down finally occurring during the
later part of next week. Dry weather is expected through the
weekend, then some rain is likely early next week as some moisture
from the southern stream gets pulled into the region ahead of an
approaching northern stream shortwave.
&&

.SHORT TERM...Today...Tonight...and Saturday
Issued at 333 AM CST Fri Feb 17 2017

The main short-term forecast issue is temperatures. Continue to
favor the warmer guidance products. The main potential pitfall
for today is if a stratus deck develops across the northeast prior
to sunrise and then persists into the day, since that would hold
back temperatures. The only obs with stratus thus far have been
KIMT and KSAW over Upper Michigan, and KIMT has since cleared.
Will keep watching, but at this point the chance of a substantial
stratus deck developing appear to be waning.

.LONG TERM...Saturday Night Through Thursday
Issued at 333 AM CST Fri Feb 17 2017

Forecast concerns revolve around temps this weekend, followed by
precip chances next week.  The medium range models continue to have
differences with their 500mb/surface features next week, and have a
slight preference for the gfs based on model comparisons.

Saturday night through Sunday night...Quiet and mild during this
period, with mid and high clouds spilling over top the mid-level
ridge that will be positioned over the western Great Lakes.  Could
see scattered to broken clouds at times, but arrival of gulf
moisture/low clouds should not arrive until Monday.  925mb temps
suggest warmer highs than inherited forecast on Sunday, but will
stay conservative due to a strong inversion.  Highs mainly in the
upper 40s to lower 50s away from the Lake and Bay.

Rest of the forecast...Clouds will be on the increase on Monday
ahead of a cold front, which will bring a swath of rain from late
Monday afternoon through early Tuesday morning across the region.
The band of precip accompanying the front should be weakening as it
moves through as the strongest upper support lifts north of the
region.  Still though, a quarter to a half inch of rainfall appears
possible.  Temps on Monday could be considerably cooler over eastern
WI with the thicker clouds arriving and a southeast wind component.
Temps should remain mild behind the front on Tuesday with a breezy
west wind.  But confidence in the sensible weather lowers
considerably due to model differences.  A moisture starved front
then drops in from the north on Wednesday into Wednesday night,
which should shift winds north or northeast, but result in little if
any precip.  This front, however, will set the stage for a large
cyclone to push into the center of the country during the late Thu
into Friday time period.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1032 AM CST Fri Feb 17 2017

Early this morning satellite imagery showed a narrow region of
LIFR stratus from near Wittenberg to Iron Mountain with the rest
of the area observing clear skies and patches of mvfr vsbys due
to haze or light fog under the surface inversion. The stratus and
light fog diminished mid to late morning. The strong inversion
continues tonight to provide more opportunities for stratus
development as surface dewpoints rise into the upper 20s to lower
30s. But winds aloft become stronger and surface winds more
westerly to promote mixing. Any stratus development may be more
focused over central and northern Wisconsin due to snow cover and
more snow melt potential today. Increasing winds aloft tonight
also provide a stretch of LLWS conditions.
&&

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

$$

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



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