Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 180915
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
315 AM CST Sat Feb 18 2017

Forecast discussion for routine morning forecast issuance

.SYNOPSIS...
Issued at 313 AM CST Sat Feb 18 2017

Unseasonably warm through the middle of next week, with some rain
late Monday and Monday night. Then turning cooler with temperatures
returning to normal by next weekend.

The upper flow across North America will remain highly split for
much of the forecast period, with the forecast area dominated by
the northern branch of the split. The southern stream will
strengthen and expand northward next week, leading to a return to
a more active weather regime for the area.

For the next 5 days, 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 a period of very mild
temperatures, except near the lake and bay where much cooler
conditions will prevail when the wind is from the east. Readings
will start a downward trend during the latter part of next week,
likely falling to near normal by next weekend.

There will be two main opportunities for precipitation. The first
will be early next week as some moisture from the southern stream
gets pulled into the region ahead of an approaching northern
stream shortwave. The second will be as a powerful cyclone in the
strengthening southern stream heads toward the area late in the
period. Those systems look like good precipitation producers, so
despite dry weather early, precipitation totals for the period
will probably end up above normal.
&&

.SHORT TERM...Today...Tonight...and Sunday
Issued at 313 AM CST Sat Feb 18 2017

The main short-term forecast issue is once again temperatures.
The east was very mild early this morning, ahead of a weak cool
front crossing the area. A few sites were near their record highs
for the day. Although 850 mb temps will fall off during the day,
with plenty of sunshine, a warm start, and westerly flow,
temperatures should warm into the lower to middle 50s across much
of the area. Went a little above a blend of ECMWF-based guidance
products for max temps today. Decreasing winds tonight and just
some high clouds should allow temperatures to drop off similar to
last night. Highs Sunday should be a little cooler than today due
to more clouds and a developing easterly flow. Again went with a
blend of ECWMF guidance products.

.LONG TERM...Sunday Night Through Friday
Issued at 313 AM CST Sat Feb 18 2017

Forecast concerns revolve around warm temperatures and precip
chances through the end of next week.  Models agree fairly well
given the complicated pattern in place, so will use a blend of the
gfs/ecmwf.

Sunday night through Monday night...Conditions will start out quiet
on Sunday night as high pressure slides to the eastern Great Lakes
and deeper moisture still off to the west.  Will have areas of high
clouds overhead and a brisk southeast wind developing which should
keep temps on the warmer side of guidance.  Conditions change on
Monday when a strong shortwave pushes low pressure into the northern
Mississippi Valley.  The shortwave will send a band of moderate rain
east across the area Monday afternoon through Monday night.  Some
guidance is producing over a half inch of rain, which appears
plausible given pwats above 1.0 inch.  Highs on Monday are tricky
since will have a southeast wind and increasing clouds, which is
usually good for cooler temps at least over eastern WI.  Precip
timing will also play a significant role too.  Will put a blend of
the ecmwf guidance for temps, which seems to be doing the best.

Rest of the forecast...Rain showers may linger over eastern WI on
early Tuesday morning, but then should see strong drying arrive from
the west through the day.  Very little cold air behind the front, so
temps will remain mild.  As a surface low passes by to our north on
Wednesday, southerly winds could bring in some of the warmest air of
the period. Some 60s look possible over central and east-central WI.
Still looking at cooler air arriving behind a southward sagging cold
front on Thursday, followed by a large cyclone arriving on Friday.  A
shallow cold airmass will be in position over the northern Great
Lakes by this time, so track of the surface low will be very
important in terms of precip types and impacts. A return to more
seasonable conditions will occur behind the system.
&&

.AVIATION...for 12Z TAF Issuance
Issued at 313 AM CST Sat Feb 18 2017

After LLWS weakens away during the mid-late morning, generally
good flight conditions are expected today into tonight. Some fog
may form tonight, but think guidance is too aggressive with the
visibility reductions and won`t go below MVFR in the TAFs.
&&

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

$$

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



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