Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 261947

Area Forecast Discussion
National Weather Service Green Bay WI
247 PM CDT FRI AUG 26 2016

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Saturday
Issued at 247 PM CDT Fri Aug 26 2016

Precipitation coverage and trends late tonight into saturday
remains the focus of this period.

This afternoon across the region...scattered but weak showers
associated with the warm air advection flow were drifting
northward over Iowa. A north to south band of convection extended
over the northern and central plains ahead of a short wave trough.
Cirrus was shifting over the state as the upper jet shifts north
in response to building upper heights. The feature of concern for
the area is the short wave over the central plains poised to
slide over the southeast half of the state later tonight into
saturday morning.

Brief medium range comparisons this morning show little deviation
with prior runs. NAM continues to be the most robust with the rain
and developing a deeper surface low tracking from southwest to
northeast across the state Saturday. The NAM is also more
aggressive with an 850 warm front and low and lifting the heavy
rain into north central Wisconsin Saturday afternoon.

Meanwhile the GFS produces briefer and more of a glancing period
of warm air advection convection over central and northeast
wisconsin through mid Saturday morning and leave much of north
central Wisconsin dry for much of the day. The GFS does produce
some precipitation on Sunday as the northern plains trough today
drifts toward the area Sunday. Nevertheless quite a significant
difference. The ECMWF run is somewhat similar to the GFS. After
this short wave passage early Saturday, appears to be a diminished
period before the northern plains trough approaches toward
Saturday evening.

Little instability tonight into Saturday and the better waa south
and the upper jet RRQ dynamics shifting north pointing to less or
shorter period rain event for Saturday.

.LONG TERM...Saturday Night Through Friday
Issued at 247 PM CDT Fri Aug 26 2016

forecast issues concern precipitation chances
Saturday night into mid week and then temperature trends later in
the week.

An upper trough tracking over the state Saturday night may still
produce some convection, but will keep pops on the lower end due
to plenty of clouds and limited instability.

After this upper trough slides through, upper heights and return
flow already starting up sunday. Reinforced WAA with increasing
surface dewpoints gradually increase MU cape values each day
Sunday into Monday. Will add a small afternoon chance of storms
sunday afternoon, otherwise the best chance for convection appear
focused toward late Monday into Monday night as a cold front
tracks through.

Later next week, a developing western state trough and upstream
ridging and further upstream troughing over the Great Lakes region
and especially over the northeast states, causing some differences
with the degree of a cool down over the Great Lakes region. GFS
provides a glancing shot of cooler air over northeast Wisconsin
for the later half of next week while the ECMWF remains milder
under the upper ridge.

.AVIATION...for 18Z TAF Issuance
Issued at 1103 AM CDT Fri Aug 26 2016

A weak trough sliding over the Great Lakes region today will
continue to produce an area of mvfr cigs across northern Wisconsin
early today then gradually lift to a lower end vfr cig before
dissipating late afternoon or early. VFR cigs expected for the
rest of the area and into tonight. Late tonight, an area of rain
with lowering cigs will approach from the south, and continue to
spread across the region through Saturday.



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