Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 160343
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1043 PM CDT Wed Mar 15 2017

Updated aviation portion for 06Z TAF issuance

.SYNOPSIS...
Issued at 240 PM CDT Wed Mar 15 2017

A round of mixed precipitation tomorrow night, otherwise
temperatures warming closer to seasonal normals.

The current large scale pattern has deep troughs over eastern
North America and over the eastern Pacific, with a modest ridge
over the inter-mountain West. The pattern will undergo a
deamplification and reamplification cycle during the first part
of the forecast period, then trend toward a more split flow regime
next week.

Temperatures will start out cool, but warm back to normal fairly
quickly. Then readings will vary between modestly above and
modestly below normal for the remainder of the period. The pattern
will support some precipitation, but probably not result in high
totals. Amounts are likely to end up a little below normal for the
period.
&&

.SHORT TERM...Tonight and Thursday
Issued at 240 PM CDT Wed Mar 15 2017

Temperatures and whether to include any PoPs late Thursday
afternoon are the main concerns in the short term.

Skies were clear across most of the forecast area today, with the
exception of some lake effect clouds and flurries in northern Door
County. A surface ridge, that was along the Wisconsin/Minnesota
border at midday, is forecast to slowly drift to the east of
Wisconsin by 18Z Thursday.

Much of the lake effect was winding down as of early this
afternoon and should continue to move away from Door County, so
there should be few, if any, clouds over the area during the
evening hours. Temperatures at 19Z were mostly in the 30 to 35
degree range and dew points were mainly in the single digits west
of the Bay and Fox Valley. Winds are expected to be on the light
side tonight, but clouds will start to move in late and there is
warm advection. With these factors in mind, lows tonight are
forecast to be in the single digits across much of the area, with
around 10 to 15 mph from the fox valley east to Lake Michigan.
Continued warm advection on Thursday, but more clouds, should
allow temperatures to warm into the middle 30s to around 40
degrees.

The 12Z GFS brought QPF into part of central Wisconsin Thursday
afternoon, but the NAM, ECMWF, Canadian, and previous forecast
were dry so Thursday has been kept dry.

.LONG TERM...Thursday Night Through Wednesday
Issued at 240 PM CDT Wed Mar 15 2017

Expect a band of precipitation to sweep east across the area
Thursday night. Forcing will be strong, as isentropic lift, QG
forcing with mid-level shortwave, and some upper support in LFQ of
upper speed max all become focused over the area. It is expected
to shift through fairly quickly, though the ECMWF remains
considerably slower than the rest of the models. The main
question will be precipitation type. Model forecast soundings
suggest the atmosphere will initially cold enough for snow, but
warming will occur fairly quickly. Maintained the wintry mix of
previous forecasts, but trended the forecast a little more toward
snow based on the ECMWF and the fact we are coming out of a cold
period, and the warming on the guidance may be a little fast. The
departing air mass will also be somewhat dry, allowing for some
evaporative cooling. Snow totals along do not look sufficient to
warrant an advisory, but freezing precipitation might. Plan to
simply detail the situation in the HWO for now.

The ECMWF is also deeper and sharper with the shortwave digging
southeast into the area Friday night. That would suggest scattered
snow showers or at least flurries. Raised PoPs some, and would not
be surprised if additional upward adjustment is eventually
necessary.

The rest of the forecast looks quieter. The following system that
crosses the area late in the weekend does not look like a good
precipitation producer. It also appears temperatures are likely to
be warm enough for primarily liquid precipitation. After a warmer
day Monday, a return to cooler weather is likely for the middle of
the week.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1043 PM CDT Wed Mar 15 2017

A dry air mass over the region will continue to produce VFR sky
CLR conditions tonight into early Thursday. Mid to high level
clouds with an approaching frontal system will filter into the
region from west to east later Thursday. Snow or snow mixed
precipitation along with deteriorating conditions will likely
begin to spread into the area starting early to mid Thursday
evening over central Wisconsin and then overnight over the rest
of area.
&&

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

$$

SYNOPSIS.......Skowronski
SHORT TERM.....MG
LONG TERM......Skowronski
AVIATION.......TDH



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