Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 212144
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
444 PM CDT SAT MAY 21 2016

Updated aviation portion for 00Z TAF issuance

.SYNOPSIS...
Issued at 146 PM CDT Sat May 21 2016

Continued warm. Increasing chances for rain during the upcoming
work week.

The large scale flow across the CONUS is highly amplified with a
deep trough centered over the intermountain West, a sharp ridge
over the Plains, and another trough over the East. The forecast
area is currently dominated by dry northerly upper flow
downstream from the Plains ridge. But shortwave energy shearing
out of the western trough will gradually flatten the Plains ridge
and nudge it east the next few days, resulting in a change to a
southwest upper flow across the forecast area for the middle to
latter part of the forecast period.

Precipitation chances will gradually return during the upcoming
work week as the large scale pattern evolves toward a regime that
will be much wetter across the forecast area. Precipitation
amounts for the whole period are likely to end up above normal.
High temperatures will remain above normal, but the warmest days
will probably occur during the early part of the forecast period
while the air mass is still drier and there are fewer clouds. Low
temperatures will warm to considerably above normal levels as
clouds and moisture increase.
&&

.SHORT TERM...Tonight and Sunday
Issued at 146 PM CDT Sat May 21 2016

High based alto cumulus clouds developed this afternoon across
northern Wisconsin. Enough enhancement in the clouds and a
few light returns on radar could not rule out an isolated
sprinkle across far northeast Wisconsin this afternoon.
Temperatures were in the 70s and lower 80s as of mid afternoon.

Weak boundary will drop southeast across northeast Wisconsin this
evening, then south of the area overnight. This boundary will only
bring a wind shift to portions of northeast Wisconsin tonight.
Followed the best performing ADJECBC guidance for minimum
temperatures tonight. Went with the ADJMETBC guidance which was
slightly warmer than the MWET/MAV guidance for highs on Sunday.

.LONG TERM...Sunday Night Through Saturday
Issued at 146 PM CDT Sat May 21 2016

The main long-term forecast challenges are determining how quickly
to spread precipitation chances across the area, and assessing the
potential for severe weather.

Not surprisingly considering the sharp upper ridge now just west
of the area, the overall trend of the models was to slow the
eastward advance of precipitation. Although a series of shortwaves
will advance across the area during the early part of the work
week, none of then appear especially strong. Also suspect that the
return of moisture will occur a little more slowly than shown by
guidance. Adjusted the forecast accordingly. Once the rain chance
arrives, the southwest upper flow suggests it will stick around
for a while--possibly through the end of the forecast period.

Any substantial risk of severe weather will be deferred to the
latter part of the forecast period, when the details of critical
smaller scale features are nearly impossible to ascertain. At this
point, the Wednesday afternoon and night time frame appears to be
have the most favorable large-scale set-up for severe weather as a
somewhat stronger/better defined shortwave is expected to cross
the region during that time. But nothing about the set-up appears
especially ominous from this far out.
&&

.AVIATION...for 00Z TAF Issuance
Issued at 444 PM CDT Sat May 21 2016

Vfr conditions to continue through monday with some
high based cumulus clouds during the afternoons.
&&

.FIRE WEATHER...
Issued at 146 PM CDT Sat May 21 2016

Elevated fire weather conditions will continue into Monday evening.
On Sunday...high temperatures should climb into the upper 70s and
lower 80s away from the Bay of Green Bay and Lake Michigan.
Afternoon relative humidity readings will be down in the upper
teens and 20s at most places, except higher near the bay and lake.
Winds will be fairly light on Sunday. Conditions will be similar
on Monday with respect to temperature and humidity, however winds
will be on the increase by late morning and afternoon with
sustained winds of 10 to 15 mph with gusts to 20 to 25 mph.
&&

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

$$

SYNOPSIS.......Skowronski
SHORT TERM.....Eckberg
LONG TERM......Skowronski
AVIATION.......RDM
FIRE WEATHER...Eckberg



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