Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 221135
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
535 AM CST Sun Jan 22 2017

.SHORT TERM...(Today through Monday night)
Issued at 237 AM CST Sun Jan 22 2017

Another morning, more fog. The visibility was being reduced the
most for locations east of the Mississippi River and then back
into east central Minnesota. Similar to the previous two mornings,
the 21.21Z SREF is doing the best at depicting where the dense fog
was located. For the rest of this morning, the SREF would suggest
no significant changes in the areal coverage of the dense fog
other than some that was located over east central Minnesota could
get advected south into southeast Minnesota. Will most likely not
make any changes to the dense fog advisory until later this
morning to see what happens after sunrise when a dip in the
visibility normally occurs.

Fog is not expected to be as big of a problem for tonight. High
pressure will start to build into the Plains States. This will set
up a more low level northwest flow which is expected to advect in
some slightly drier air. So, while some fog will likely be around
again tonight, at this time it is not expected to be dense. The
area of high pressure will then move across the region for Monday
and Monday night for a couple of periods with quiet weather.

.LONG TERM...(Tuesday through Saturday)
Issued at 237 AM CST Sun Jan 22 2017

Water vapor satellite this morning is showing the next system was
currently off the northern California and Oregon coasts over the
Pacific. The 22.00Z models all showing differences on how this
system is handled once it comes inland and moves across the
Rockies. The NAM solutions definitely looks to be out of line
compared to the other models as it looks to be too flat with the
short wave trough and never develops a closed upper level low. The
ECMWF and GFS are much more similar with the system, although the
GFS continues to be faster with it. As the main short wave trough
crosses the Rockies Tuesday, a closed upper level low is expected
to form over Nebraska. These two features will then move
east/northeast across the Midwest Tuesday night and Wednesday. A
round of weak to moderate pv advection in the 500-300 mb layer
should move across the southern half of the area Tuesday afternoon
and evening. The surface low is still expected to come out of
Kansas and move across southern Iowa and into norhtern Illinois or
southeast Wisconsin from Tuesday through Wednesday morning. This
should place the best low level warm air advection and isentropic
up glide across the southern sections of the forecast area. Would
expect a band of mid level frontogenesis to develop north of the
surface low which is where the best qpf and snowfall should occur.
The ECMWF has shown the most continuity with this system and
continues to show this band of higher QPF and snowfall occurring
from about Interstate 90 and south for Tuesday afternoon and night
before the whole system moves past the area with just lingering
light precipitation into Wednesday. Currently expecting a band of
2 to 4 inches of snow across the area with the highest totals
along and south of Interstate 90.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 535 AM CST Sun Jan 22 2017

The period will start out with IFR/LIFR conditions in BR/FG and low
cigs. Conditions will slowly improve thru today/tonight as drier
high pressure slowly builds east into the Upper Midwest. However,
even by later this afternoon and tonight, conditions are looking to
remain IFR with the low stratus/cigs remaining over the area. Some
vsbys looking to improver to MFVR, perhaps even VFR in the river
valleys (KLSE). Given the generally light low level flow and plenty
of low level moisture/boundary layer moisture loading from snow melt
trapped in/under a shallow inversion or isothermal layer, tended to
stay a bit more pessimistic with the TAFs/conditions thru the
period. Even Monday, as the lower level ridge axis would move across
the region, looks to remain IFR/MVFR cigs with the lower level
moisture being very tough to scour out.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Dense Fog Advisory until noon CST today for WIZ017-029-032>034-
     041>044-053>055-061.

MN...Dense Fog Advisory until noon CST today for MNZ079-086>088-
     094>096.

IA...Dense Fog Advisory until noon CST today for IAZ008>011-018-019-
     029-030.

&&

$$

SHORT TERM...04
LONG TERM....04
AVIATION.....RRS


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