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Area forecast discussion
National Weather Service Green Bay WI
1032 PM CDT Wednesday Apr 16 2014
Updated aviation portion for 06z taf issuance
Short term...tonight and Thursday
issued at 313 PM CDT Wednesday Apr 16 2014
Major late winter storm continues to be the primary focus for the
short-term part of the forecast. Expect to see a lull in the snow for
a time late this afternoon/early evening...before the snow returns
later this evening through Thursday morning. Exact snow accumulations to
be biggest forecast headache...especially the farther south one GOES.
The 19z msas surface analysis showed an area of low pressure over northwest Iowa
with a warm front extended east/then southeast into central Illinois. A cold front
stretched from the surface low southwestward through the Central Plains. Inital
surge of snow now over far northern WI with the main band of snow
located over Minnesota.
The surface low is forecast to move from northwest Iowa northeastward to west-central WI tonight
with heavy snow falling to the north and west of the storm track.
The heavy snow will continue in part due to a strong baroclinic zone
thanks to a 45 knots southerly low-level jet aimed at WI. Farther
aloft...a middle-level shortwave trough to provide the needed forcing
and a favorable right entrance region to the upper jet to provide
additional lift. Northern WI to remain directly under the main brunt of
the snow with additional accumulations of 5 to 8 inches by
daybreak. Central/E-cntrl WI to see the lull in the action for a
time this evening before better forcing/lift arrives during the
overnight hours ahead of the cold front. Thus...have focused the likely
probability of precipitation after midngt for these locations with precipitation type likely a
rain/snow mix changing to snow late over central WI. Based on
expected less snow amounts for Marathon County...will drop the advisory
for that County only.
Surface low tracks across north-central WI Thursday morning and eventually
reaches Lake Superior by Thursday evening. Northern WI could see an
additional 1 to 3 inches of accumulation Thursday morning which would
bring totals into the 8 to 16 inch range (highest values in Vilas
county). The precipitation should diminish Thursday afternoon as the system
pulls away...but clouds will remain through the rest of the day. Maximum
temperatures to range from the upper 30s far N-cntrl...to the upper 40s west
of the Fox Valley.
Long term...Thursday night through Wednesday
issued at 313 PM CDT Wednesday Apr 16 2014
Upper flow remains cyclonic Thursday night and then
weak upper ridging follows for Friday through Saturday afternoon.
It could get very cold in north central Wisconsin Thursday night
if skies could clear. Not sure if they will with upper trough over
the area so did not go as cold as it could get if skies clear.
Leftover clouds and northerly winds coming off snow covered ground
to the north should keep it cool Friday.
A strong upper trough moving across southern Canada while another
moves across the Southern Plains are the primary weather makers
for Saturday night through Monday. The GFS and European model (ecmwf) agree on an
area of showers moving through Saturday night but differ on how
quickly a surface front moves through Easter Sunday. The European model (ecmwf)
holds up the front though Monday with overrunning rains while the
GFS brings it through Sunday afternoon. The unusually cold and
dry air to our north might just push the front through Sunday
afternoon so that is where we are leaning right now. Warmer
weather expected Monday and Tuesday.
Aviation...for 06z taf issuance
issued at 1024 PM CDT Wednesday Apr 16 2014
Conditions will vary greatly overnight...from MVFR/IFR across the
north due to low clouds and snow...to VFR across east central Wisconsin.
Snow will continue through Thursday morning across the north...and then
end during the afternoon. Across northeast and east central Wisconsin....
a mix of rain and snow (primary snow) should move into this portion
of the state towards 12z. Did continue some low level wind shear
about 1600 feet off the ground around 160/170 degrees at 40 to 45 knots.
Conditions will improve into the VFR category Thursday afternoon
as the low pulls away. Will need to take a look at cloud cover
tomorrow night and determine if there is any fog potential due to
lightening winds and maybe a decrease in the clouds.
Winter Storm Warning until 1 PM CDT Thursday for wiz005-010>012.
Winter Weather Advisory until 1 PM CDT Thursday for wiz013-018-