Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 222348

Area Forecast Discussion
National Weather Service Green Bay WI
648 PM CDT MON AUG 22 2016

Updated aviation portion for 00Z TAF issuance
and new information added to update section

Issued at 636 PM CDT Mon Aug 22 2016

Scattered showers and thunderstorms developed over northern WI
during the late afternoon, in response to increasing H8 WAA and
800-700 mb frontogenetic forcing. A few storms have been strong,
and likely produced at least half inch hail, though no reports
have been received so far. These storms should weaken as they
move into a more stable air mass over far northeast WI, and
exit the region before midnight.


.SHORT TERM...Tonight and Tuesday
Issued at 249 PM CDT Mon Aug 22 2016

Forecast issue for the rest of this afternoon into tonight
centers on the potential for convection to develop with the
increasing WAA pattern over the northwest half of the state.
Satellite imagery shows diurnal cu this afternoon with a
gradually expanding band of mid level clouds over western Wisconsin.
Morning Pwats for GRB were only 0.71 and slightly higher at msp
around 1.00 inches. Medium range progs persistent with developing
isolated showers around MSP mid afternoon and then lifting into
North Central Wisconsin by early evening. GFS actually developed
around 15z and not initializing well at the onset. An earlier HRRR
short range run lifted convection more toward central Wisconsin
by late afternoon or early evening before dissipating, but later
runs are focusing more toward North Central Wisconsin. Expect any
convection which develops to be very isolated due to limited
moisture so certainly do not want to expand on the current small
chance over North Central Wisconsin into Central Wisconsin.
Strongest waa with a LLJ of 40 to 50 kts working into Northeast
Minnesota and northwest Wisconsin late afternoon and evening, and
upper heights on the increase this afternoon into tonight. If and
where convection develops, westerly winds at the 700 mb will
likely produce an easterly flow due to storm motion.

Expect a dry day for Tuesday along with warmer and more humid
conditions as upper heights continue to build ahead of the strong
trough dropping into the Northern Plains. Day time high
temperatures to get into the lower to mid 80s for at least one

.LONG TERM...Tuesday Night Through Monday
Issued at 249 PM CDT Mon Aug 22 2016

A warm front may bring showers and thunderstorms
late Tuesday night and early Wednesday as it lifts north across
the area. There is just weak instability and high wet bulb zero
heights but some shear. Low temperatures will be held up due to
clouds and a steady south wind.

A surface wave and cold front should move through Wednesday
during the midday hours. Cloud cover will reduce surface based
instability but convergence along the front argues for at least
the chance of a strong or marginally severe storm. Cooler and
drier air lags behind the front and doesn`t really arrive until
Thursday. Dry and pleasant weather is likely Thursday through much
Saturday as a surface high moves across the western Great Lakes.

The upper flow is expected to become southwest Saturday afternoon
with an increasing chance of precipitation Saturday night and
Sunday as jet energy approaches from the central Plains and low
level winds bring warmer and more humid air in from the southern

.AVIATION...for 00Z TAF Issuance
Issued at 636 PM CDT Mon Aug 22 2016

Scattered showers and thunderstorms will move out of northeast WI
later this evening, followed by generally dry conditions for the
rest of the TAF period. Other than an isold shower at RHI early
this evening, do not expect any impact to the TAF sites. Steady
surface winds and strong boundary layer winds should prevent any
fog formation from occurring overnight.

The main aviation threat will be LLWS, which will develop by mid-
evening and continue overnight, as southwest winds increase to 35
to 40 kts about 1000-1500 feet AGL. The LLWS will taper off early
Tuesday, but sfc winds will increase again with the heating of the
day, with gusts to 20 to 25 kts anticipated in the late morning
and afternoon.




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