Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 200439

Area Forecast Discussion
National Weather Service Green Bay WI
1039 PM CST Thu Jan 19 2017

Updated aviation portion for 06Z TAF issuance

Issued at 406 PM CST Thu Jan 19 2017

Freezing precipitation and areas of fog are likely to impact
travel tonight, and possibly again Friday night. Otherwise, much
above normal temperature expected for the next week.

The upper flow across North America will become increasingly split
and blocky the next several days as a large positive upper height
anomaly retrogrades across Canada while a negative anomaly expands
east across the southern CONUS. The split flow favors much above
normal temperatures, though readings may begin to trend back
toward normal late in the period once the positive anomaly
reaches northwest Canada. Precipitation chances will depend
primarily on southern stream systems reaching the area. A couple
modest systems are likely to affect the area early in the period,
though the strongest system will likely pass to the south during
the weekend. The early systems combined with a system next week
will probably be sufficient to result in above normal
precipitation amounts for the period.

.SHORT TERM...Tonight and Friday
Issued at 406 PM CST Thu Jan 19 2017

A system moving into the region from the Plains will bring rain to
the area tonight. Much of the rain is expected to fall in
locations where air temperatures or ground/pavement temperatures
are forecast to fall below freezing overnight.

Fog developed across the area last night, with dense fog over
central and north central Wisconsin. The visibility finally
improved by midday in most places, and much of the stratus cleared
out as well. Temperatures in the north, where it cleared earlier
in the day, reached the 40s while the rest of the area was mainly
in the lower to middle 30s.

Models had QPF moving into the forecast area after 00Z. Stuck
closer to the 12Z NAM and ECMWF timing, which was faster than the
GFS or Canadian. There was some light rain in southwest Wisconsin
at 21Z, so faster may work out better. Based on forecast
soundings, any ice should melt in the warm layer aloft so freezing
rain, or rain that freezes when it comes into contact with a
subfreezing surface, seems the most likely weather type across
much of the forecast area as temperatures fall below freezing.
Some locations will likely see a glaze of ice develop as roads and
sidewalks cool off, even with air temperatures above freezing.
This occurred in Green Bay with our recent ice storm.

Have a freezing rain advisory for central Wisconsin, but there
could be some light icing farther to the east and north. Will have
to wait and see how things unfold.

.LONG TERM...Friday Night Through Thursday
Issued at 406 PM CST Thu Jan 19 2017

Initial shortwave will be weakening over northern Wisconsin early
Friday evening, with a second one following closely later in the
night. Temperatures aloft and air temperatures will be warm enough
to produce mainly rain, though METRO road data suggest pavement
temperatures at locations north and west of the Fox Valley could
fall below freezing again at night. That effect should lessen as
the warmup continues, but will continue to mention at least the
possibility of freezing rain Friday night.

Discerning the details of the remainder of the forecast is
difficult. A strong cyclone is likely to track from the southern
Plains to the mid-Atlantic states late in the weekend and early
next week. Troughing extending back northwest from that system
will likely linger across the area, possibly resulting in light
precipitation at times. Temperatures should warm enough for the
precipitation to be primarily liquid. Fog will be likely as well,
at least until the snow/ice cover begins to disappear.

A gradual trend toward colder conditions is likely to begin by the
middle of next week. By the time a storm system heading east from
the Plains during the latter part of next week reaches the area,
temperatures may be cold enough for mainly snow. Further cooling
is likely behind that system, with readings probably back close to
seasonal normals by the last weekend in January.

.AVIATION...for 06Z TAF Issuance
Issued at 1039 PM CST Thu Jan 19 2017

IFR conditions expected over most of the area through 18z Friday
due to low clouds and fog. In addition, light rain or freezing
rain will move in from the south late tonight and continue early
Friday. Ceilings and visibilities will rise slowly Friday
afternoon as the precipitation ends. &&

Dense Fog Advisory until 9 AM CST Friday for WIZ011>013-021-022-

Freezing Rain Advisory until 10 AM CST Friday for WIZ030-035-036-

Freezing Rain Advisory until 10 AM CST Friday for WIZ018>020-031-


LONG TERM......Skowronski
AVIATION.......RDM is the U.S. government's official web portal to all federal, state and local government web resources and services.