Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 191129

Area Forecast Discussion
National Weather Service La Crosse WI
529 AM CST Sun Feb 19 2017

.SHORT TERM...(Today through Monday)
Issued at 255 AM CST Sun Feb 19 2017

Another gorgeous, April-like Spring day to round out the weekend.
Highs reached/topped 60 for some yesterday, and expect something
similar for today. Some high thin clouds moving in from the west the
only mar on the skies and potential deterrent to the warming.

Models in good agreement with lifting an upper level shortwave out
of the desert southwest today, merging it with a bit of energy
moving east/northeast out of the Pac NW. This elongated shortwave
trough is then slated to push into western MN by 18z Mon, exiting
east overnight. Decent although narrow frontogenetic forcing along
its associated sfc front with a slug of low level warm air
advection. The moisture is the most impressive part of this weather
system. NAEFS pw anomalies are +4 to +5 for Monday with a strong
push of 850 mb moisture transport ahead of the sfc front. To say
this is rare for mid Feb is an understatement. NAM/GFS suggest a
little instability that the front could play with, only 200-400 J/KG
MUCAPE, but could be enough for a few cracks of thunder, mostly in
the south.

Thankfully this system is moving through rather quickly, and
orientated north-south. Slower, more west-east banding would result
in a lot more qpf, and heighten the risk for rises/flooding on area
waterways and/or possible ice jams (where ice still exists). Those
with river interests will have to pay close attention over the next
week. Runoff from the warmth is already causing rises.

.LONG TERM...(Tuesday through Friday)
Issued at 255 AM CST Sun Feb 19 2017

Winter isn`t done with us yet.

Potent winter storm still has its sights set on the region for Thu
night - Friday, although latest GFS/EC have shifted the storm track
farther south compared to their previous 00z runs. Good agreement
though between the two. Probably see additional fluctuations in
movement on the storm track over the next few days too, before
settling in in a couple days.

What hasn`t changed is strength of the system - it still looks to be
packing quite a punch.

Upper level trough slated to move out of the desert southwest late
Wed night, lifting northeast across the Oh River Valley Friday
evening. The system`s sfc low shifts from the southern Plains to
across northern Ill by 18z Fri. Deep, strong qg convergence
through the layers, centered across the forecast area at 18z Fri.
North-south running x-sections shows sloping frontogenetic region
spreading northward from the low, with some hints of weak -epv above
it, suggesting enhanced pcpn bands. The cherry on top is a coupled
300 mb jet enhancing the lift from thu night-fri.

While not currently as anomalously wet as the Monday system, still a
nice fetch of low level moisture for the storm work with. The 850 mb
moisture transports noses into central Ill, but the system will
wrap that north/west of the sfc low.

It will be quite mild leading into the storm, and temperatures will
play a role in what falls and how much. Time/height x-sections and
bufkit soundings currently point to a snow/rain discussion rather
then a wintry mix - a nice change from recent storms that have been
all about the winter mixed bag. Certainly could change. In addition,
grounds/roads have been warming, and will continue through the
better part of the new week. Accumulating snows will have to battle
that at the onset. That said, given the forcing, snowfall rates
would likely quickly overcome any warm ground considerations.

With a relatively warm/wet airmass in place, snow ratios generally
look to be around and south of 15:1 at this time. Too early to paint
max amounts in the heart of the storm`s snow band, but many inches
are favored.

If the storm continues to hold its progged strength, Winter Storm
Watches for Thu Night-Friday are likely. Where, is of course,
dependent on the track. It has the "feel" of a spring storm we would
usually see more mid March rather than Feb.

Stay tuned...


.AVIATION...(For the 12Z TAFS through 12Z Sunday night)
Issued at 529 AM CST Sun Feb 19 2017

MVFR/IFR BR/FG has formed across parts of SE MN/NE IA early this
morning, and was being advected into the KRST area as of 11z.
Appears the BR/FG is rather shallow with the vsby restrictions but
little in the way of low clouds/cigs with it. Expect this to
lift/burn off in the 14z-16z time period with and increase of sfc-
925mb winds and the shallow nature of the fog. After that, generally
good VFR expected with clouds thru tonight increasing but mainly at
or above 15k ft. S/SE sfc winds to increase today/tonight as the
pressure gradient tightens, but remain mostly in the 7-13kt range
thru the period. Tighter pressure gradient just above the sfc again
tonight, for LLWS concerns. By late evening S-SW 925mb winds progged
in the 35kt range while sfc wind more S-SE at the 7-13kts. Added
LLWS mention to both tafs for the later evening/overnight hours as a
heads up for changing wind direction/speed on descent or climb-out.


Issued at 530 PM CST Sat Feb 18 2017

5 PM Update: No records set again today, but we were close,
especially at La Crosse. Still thinking there is a pretty good
chance at least La Crosse will break the record on Sunday, and
potentially Monday though that will depend on how fast clouds
and rain increase. Rochester may lag behind just a few degrees
from current records, but it will be close. Regardless, still an
incredible stretch of spring-like warmth for this time of year.

Below are the records for La Crosse and Rochester through
Wednesday February 22nd:

                          Record Highs

             La Crosse                     Rochester
            -----------                   -----------

Sun (19th)    59/1930        Sun (19th)     59/1930
Mon (20th)    61/1930        Mon (20th)     60/1930
Tue (21st)    64/1930        Tue (21st)     60/1930
Wed (22nd)    62/1984        Wed (22nd)     59/1930

                         Record High Lows

Sun (19th)    38/2002        Sun (19th)     36/2002
Mon (20th)    41/1930        Mon (20th)     34/1954
Tue (21st)    48/1930        Tue (21st)     39/1930
Wed (22nd)    39/1930        Wed (22nd)     42/1930


MN...Dense Fog Advisory until 9 AM CST this morning for MNZ094.

IA...Dense Fog Advisory until 9 AM CST this morning for IAZ008-009-


LONG TERM....Rieck
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