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Area forecast discussion 
National Weather Service La Crosse WI
324 am CST Monday Dec 29 2014

Short term...(today and tonight)
issued at 324 am CST Monday Dec 29 2014

Temperatures...wind chill and associated headlines will be the
primary concerns through mid-week. 29.00z model suite in
excellent agreement through Wednesday...then diverging Thursday
through the weekend. Forecast confidence is low by Saturday/Sunday
as GFS/European model (ecmwf) differ significantly with timing and track of Four
Corners trough as it ejects east.

For today...snow will stay well south and west of the upper MS
River Valley along leading edge of Arctic air mass diving into
the north-central Continental U.S.. could see some scattered flurries across
extreme southwest extent of forecast area...but not expecting any
accumulation. Clouds will very slowly erode from northwest to
southeast late this afternoon/evening and into tonight. Under
persistent cold air advection regime...temperatures today to be a
solid 5 to 10 degrees colder than yesterday with the coolest
readings in the upper single digits and low teens across the snow
covered northwest.

Skies will clear out by Tuesday morning...allowing temperatures to
drop into the single digits above and below zero. Northwest winds
will be strongest (10 mph) across southeast Minnesota and northeast Iowa
resulting in wind chill values from 15 to 25 below zero. Will
issue a Wind Chill Advisory for the western third of the forecast
area from 06z tonight until 18z Tuesday. Hazardous wind chills
also possible across Taylor/Clark counties...but for ease of
collaboration with surrounding offices...will not issue any
headlines for these areas at this time.

Long term...(tuesday through sunday)
issued at 324 am CST Monday Dec 29 2014

Tuesday will be mostly sunny...but the coldest day of the week with
high temperatures in the single digits for all areas except for
small portions of northeast Iowa and southwest WI. Northwest wind
around 10 miles per hour will keep wind chill values below zero through the
day. 925 hpa temperatures bottom out around -20 c by 06z Wednesday...
dropping surface values by Wednesday morning to zero or less for
all areas. West-southwest wind remains elevated through the night
on north-northeast periphery of 1046 to 1048 hpa surface high.
Will need another Wind Chill Advisory Tuesday night/Wednesday
morning for at least all areas currently snow covered and maybe
even another tier of counties to the south with wind wind chills
from 20 to 30 below zero.

Winds shift to the west-southwest Wednesday through Friday under
broad warm air advection regime. In fact...southwest winds will be
quite breezy Wednesday from 15 to 25 miles per hour given 30 to 40 kts in the
boundary layer inversion. Although Wednesday will still be quite
chilly with wind chills below zero...temperatures will rise each day
thereafter with highs by Friday in the 20s to near 30 degrees.

GFS/European model (ecmwf) differ with timing and extent of possible light snow event
Thursday/Friday across the northern forecast area as a weak
short-wave moves through parent northwest flow aloft. GFS has
snow on Thursday vs the European model (ecmwf) on Friday. Will split the difference
with 20 probability of precipitation both days mainly across north-central Wisconsin.
With either solution...accumulations appear minimal.

GFS ensembles show a massive spread in possible tracks for the
weekend Four Corners trough...depicting anything from a closed low
across northern Mexico to an open wave across the Great Lakes. In
addition...the 29.00z European model (ecmwf) is also significantly different than
24 hours ago with the majority of precipitation falling across the Ohio
River valley into the Middle-Atlantic States. Will keep 20 to 30 probability of precipitation
across much of the forecast area Saturday into Sunday more or less
for continuity/S sake...but confidence is very low. If there is a
trend in the would be for a drier weekend than
previously forecast. With all these differences...there is also a
wide spread in temperature guidance for the weekend. Will follow a
middle-of-the-Road approach with highs in the 20s and lows in the


Aviation...(for the 06z tafs through 06z Monday night)
issued at 1105 PM CST sun Dec 28 2014

Areas of 1 kft clouds hanging across southwest Minnesota late this
evening...but mesoscale models are Adamant that these will stay west of
krst. Instead...high level clouds are expected to continue to filter
across the region tonight/Monday...staying VFR.


Arx watches/warnings/advisories...
Minnesota...Wind Chill Advisory from midnight tonight to noon CST Tuesday
for mnz086-087-094-095.

Iowa...Wind Chill Advisory from midnight tonight to noon CST Tuesday
for iaz008-009-018.



Short term...Rogers
long term...Rogers

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