Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 261724
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1224 PM CDT TUE JUL 26 2016

Updated aviation portion for 18Z TAF issuance

.SHORT TERM...Today...Tonight...and Wednesday
Issued at 300 AM CDT Tue Jul 26 2016

Primary forecast issue today into Wednesday will be precipitation
chances spreading from north to south with a slow moving cold
front approaching from the north.

Early this morning high pressure was drifting eastward over the
Great Lakes Region. Patchy fog was noted over a few locations.
Nearest convection was noted over the Northern Plains in the warm
air return region and south of a cold front sagging toward the
US/Canada border.

Progs begin in good agreement with a cold front reaching northern
Wisconsin tonight before dropping into central Wisconsin during
Wednesday morning. Progs then divert on the movement of this front
later Wednesday as upper heights continue to fall over the Western
Great Lakes region while a short wave or a series of short waves
originating form the NW states may become in the mix during peak
afternoon heating. A RRQ region will be brushing over northeast
Wisconsin as an upper jet north of the great lakes region sags
south.

H850 temp prod will work into northern Wisconsin ahead of the
front this afternoon and evening. Will continue with afternoon pop
mention far north even though the high pressure region drifting
east will dominate most of the day. MU capes climb to 1500 j/kg
today, with the highest values over the north half of the state.
Depending on cloud cover, MU capes progs may again climb to near
1800 to 2000 j/kg over central Wisconsin on Wednesday as the front
continues to drop southward. Highest total totals into the lower
50s occur this evening over the north half of the state...with a
marginal risk of severe storms still highlighted. Will need to
account for this instability ahead of the front this afternoon and
tonight but still will focus primary precipitation chances with
the convergence near the front.

.LONG TERM...Wednesday Night Through Monday
Issued at 300 AM CDT Tue Jul 26 2016

Precipitation trends are the main concern during the long term
forecast.

00Z models seemed consistent with the general idea of an upper
level trough over the region during the middle of the week slowly
moving east with a ridge building over the Plains and making it to
the Great Lakes by early next week. This would suggest a gradual
warming trend and drier weather for the weekend into early next
week.

There are quite a few differences in the finer details, resulting
in a less than desirable forecast confidence level. Just for
example, at 12Z Friday the 00Z NAM had a surface low centered in
eastern Virginia, the GFS had it in southern New Jersey, the
Canadian had it in eastern Kentucky, and the ECMWF had a much
weaker low in central Illinois.

The significant differences among the models appear to justify
using a model blend, or combination of model blend and the
previous forecast, for the long term forecast. The best chance
for showers and storms looks to be mainly late in the work week,
with slight chances or no mention of rain at all for the Saturday
through Monday.

Highs should be a little below normal for Thursday and Friday,
before warming to a few degrees above normal by Monday.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1223 PM CDT Tue Jul 26 2016

A cold front is expected to slowly drop south across WI starting
this evening across northern WI and eventually reaching southern
WI by late Wednesday. There will be a chance of showers and
thunderstorms associated with this frontal boundary, primarily
across the north tonight. As the front continues to sag south on
Wednesday, a mid-level shortwave trough is forecast to push
across the Upper Midwest and increase the areal coverage of
showers/storms across northeast WI, especially during the
afternoon hours. While VFR conditions would predominate over the
next 24 hours, expect some patchy fog later tonight and
precipitation to lower vsbys to MVFR conditions at times.
&&

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

$$

SHORT TERM.....TDH
LONG TERM......MG
AVIATION.......AK


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