Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 252321

Area Forecast Discussion
National Weather Service Green Bay WI
621 PM CDT WED MAY 25 2016

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Thursday
Issued at 216 PM CDT Wed May 25 2016

The latest RAP analysis and satellite/radar imagery show low
pressure centered over northeast South Dakota early this afternoon.
A stationary front stretches east-southeast across southern
Minnesota to just north of Milwaukee.  With southwest flow
aloft...shortwave activity is moving across Minnesota and Iowa...and
is helping to generate clusters of showers and storms...with some
support from moisture convergence along the front.  ML capes are
approaching 1000 J/kg over southwest Wisconsin early this afternoon
where the first severe thunderstorm warning has been issued.  As
storms move northeast this afternoon...potential exists for a severe
storm to carry into central WI.  Severe and heavy rain potential are
the main forecast concerns in the short-term.

Tonight...The stationary front will return northward tonight as a
warm front...with some forward push provided by shortwave energy
moving northeast over the northern Mississippi valley. As pwats
climb to 1.6 inches ahead of the wave...the hi res models continue
to indicate that a swath of showers and storms will shift northeast
across the forecast area this evening.  But these models have a
slightly different playbook for tonight...some giving north-central
WI decent rainfall...while others show the heaviest rainfall moving
over central and northeast WI.  Sided with the former of the two
scenarios based on recent radar trends.  Regardless...rainfalls of a
half inch to an inch will be possible...locally over an inch in the
stronger storms.  If there is a severe weather chances
appear to be over central WI later this afternoon into early this
evening.  Progged RAP soundings near Wisconsin Rapids show ML capes
are expected to range from 800-1000 J/kg later this afternoon...with
0-6km bulk shear of 35 kts...and mid-level lapse rates greater than
7 C/km. These parameters suggest a low end damaging wind and large
hail threat are possible.  The threat of severe weather will
diminish rather quickly farther north and east...where the airmass
is more stable.  The showers and storms will be exiting northern WI
late in the evening...then a low overcast will settle in as a warmer
airmass arrives.  Some potential for a shower or storm to pop up
late tonight...but warm advection is relatively weak...and the
atmosphere will have been worked over for the most part.  Rather
muggy lows in the upper 50s to low 60s.

Thursday...Northern Wisconsin will begin the day in the warm
sector...with rather cloudy/foggy skies.  The small chance of a
shower/storm will carry over from late tonight into Thursday
morning.  Then should see clouds give way to increasing sunshine
from late morning thru early afternoon.  This will promote temps
warming into the low to mid 80s at most locations in the afternoon.
Combined with dewpoints in the low to mid 60s...ML capes are
expected to rise between 1500 and 2500 J/kg during peak
heating...with bulk shears upwards of 35 kts.  However...tough to
find a trigger for any storms.  Will go with a slight
chance...though highest over north-central WI...closer to shortwave
activity.  If any storms fire...pulse severe is possible.

.LONG TERM...Thursday Night Through Wednesday
Issued at 216 PM CDT Wed May 25 2016

An upper-level low pressure trough over the western U.S. will
continue to generate warm and moist southerly winds in Wisconsin
Friday through Sunday...with mild temperatures and a round or two
of showers and thunderstorms during that time. Severe
thunderstorms are possible but will generally be isolated.

The upper level trough will gradually expand east and weaken by
early next week...producing a more zonal pattern and somewhat
cooler temperatures.

.AVIATION...for 00Z TAF Issuance
Issued at 621 PM CDT Wed May 25 2016

A warm front will lift northeast across the area
tonight. there is a good chance of showers and thunderstorms until
the warm front goes by. after the precipitation ends some low
clouds and fog are possible late tonight through early thursday.
scattered showers and thunderstorms are possible again around
midday thursday.



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