Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 171953
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
253 PM CDT SUN JUL 17 2016

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Monday
Issued at 251 PM CDT Sun Jul 17 2016

The latest Rap analysis and satellite/radar imagery show the
decaying mcs exiting the tip of the Door Peninsula early this
afternoon.  Plenty of low clouds exist behind the system, but
anticipate partial clearing moving into central and north-central WI
later this afternoon.  Meanwhile, a cold front is sliding southeast
across northwest Wisconsin.  There is a wedge of mostly sunny skies
nosing northward ahead of the front, where temps are rising into the
upper 70s to low 80s.  However, aircraft soundings from Minneapolis
from earlier this morning show a substantial cap in place.  The
latest Rap soundings also show a similar cap between 700-800mb.
There remains a low chance that this cap will erode enough with
further heating for thunderstorms to develop, mainly after 21z.
Though ml capes could reach from 600-1000 j/kg, the cap combined
with ample mid-level dry air will likely limit coverage and severe
potential.  Therefore think only isolated severe storms will be
possible at best, and will lower thunderstorm chances between 30 to
40 pct for the rest of the afternoon. Thunderstorm potential remains
the main forecast concern in the short term.

Tonight...The cold front will finish moving across central and
northeast WI during the evening hours, before ending up over
southeast lower Michigan and northern Illinois overnight.  The same
concerns listed above will carry over into the evening hours, in
regards to potential for convection.  Will leave a small chance in
the forecast through about 10-11pm in case capping can be overcome,
but limited instability and dry mid-level air will keep the severe
threat as isolated. Will mostly likely be looking at sub-severe
gusty winds and small hail within any storms.  Behind the front,
will see a band of clouds arrive as winds shift to the northwest. No
precip is expected out of the clouds.  Then should see clearing
conditions overnight.  Low temps falling into the upper 50s north to
mid 60s near Lake Michigan.

Monday...High pressure will be building in behind the front.  Should
see plenty of sunshine within a less humid airmass.  Only scattered
diurnal cu should form with heating of the day.  Highs in the mid
70s north to low 80s south.

.LONG TERM...Monday Night Through Sunday
Issued at 251 PM CDT Sun Jul 17 2016

An upper ridge over the western Plains is forecast to build and
move slowly east this week. As it does so a surface high over the
Great Lakes moves east and a southerly flow of air brings increasing
warmth and moisture from the south.

The southern edge of the westerlies are not too far away, so there
is at least a small chance that some convection or a back door
front could provide some partial relief from the heat, but if not
we will have the hottest weather of the summer so far this
Thursday and Friday.

Monday night through Tuesday night should have comfortable
humidity levels but then dewpoints will climb as southerly flow
increases. Thunderstorms are possible ahead of a warm front
approaching from the southwest late Tuesday night and Wednesday.
There could also be an MCS somewhere in the vicinity Wednesday
night. Thursday and Friday should be hot and humid, but convection
will probably be subdued by warm mid level temperatures.

Record highs are in the low to mid 90s Friday, so it is possible
some of these could be tied or beaten. Heat indices of 100F or
higher are likely if dewpoints rise into the 70s as currently
expected.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1205 PM CDT Sun Jul 17 2016

A large area of mvfr cigs, locally ifr in mist, will persist across
the region through early afternoon.  Then should look for improving
cigs as partial clearing works into the region ahead of a cold
front.  This cold front will pass across the taf sites from late in
the afternoon through mid evening, with a low chance of additional
showers and thunderstorms along it.  Probability is too low to
include in the tafs. Once the front clears the region, skies are
anticipated to clear and winds should diminish.  Good flying weather
should then continue through the end of the taf period.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Beach Hazards Statement until 10 PM CDT this evening FOR WIZ022-
040-050.
&&

$$

SHORT TERM.....MPC
LONG TERM......RDM
AVIATION.......MPC


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