088 
FXUS63 KMPX 171946
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
146 PM CST Sun Feb 17 2019

.SHORT TERM...(This evening through Monday night)
Issued at 135 PM CST Sun Feb 17 2019

Light snow event to the north of an h5 low down over IA will slowly 
wind down through the afternoon as that low slowly gets sheared out 
and absorbed into the main flow associated with the 150-180 kt upper 
jet from the TX Panhandle to western New York. Snow reports have 
been somewhat underwhelming when compared to what was forecast and 
the culprit has been the snow ratios. Weak lift in the dendritic 
growth zone has resulted in more a thin needles and plates type of 
crystals, which has resulted in snow ratios down closer to 10:1 as 
opposed to up in the 18-20:1 range. Biggest nearby snow report we've 
seen so far was from Austin with 4.3", which is about 1-1.5" 
lower than we were forecasting. Another example of the next nut we 
have yet to crack when it comes to forecasting snowfall is 
determining crystal types that will be generated and the resultant 
snow ratio.

Not much happening the rest of the short term as we have a 1040mb 
high incoming. The main question tonight through Monday night is 
what will the extent of cloud cover be. We look to mostly clear out 
the mid-level clouds Monday/Monday night, but the question is how 
much, if any status do we see.  Forecast soundings are fairly robust 
with their low level moisture and stratus potential, but think this 
is a bit overdone and we'll see partly cloudy skies on the whole 
Monday/Monday night. With the lower cloud cover in mind, did lower 
forecast lows a few degrees from the previous forecast for Monday 
night, though there's potential for them to be several degrees lower 
depending on what we see for cloud cover.

.LONG TERM...(Tuesday through Sunday)
Issued at 135 PM CST Sun Feb 17 2019

The anomalous longwave trough will remain over the Western CONUS 
with anomalous ridging over the Southeast CONUS through this 
period. So, the active weather pattern will continue with mostly 
below normal temperatures

The threat for accumulating snow continues for Tuesday night and 
Wednesday. This system is somewhat similar to today's on-going 
system with a mid-level closed low forming and aided lift from an 
inverted surface trough behind a surface low. With the jet becoming 
more meridionally-oriented, the mid-week system will have a more 
northerly track than today's system. This will bring more forcing 
over MN/WI, and better potential for more widespread 3-6 inches of
snowfall. There are still differences in the exact location of 
this system with the 17.12 GFS continuing to show the deepening 
surface low crossing through the IA/WI/IL border at 18Z Wednesday 
and the heaviest snowfall totals over IA. The 17.00 ECMWF showed 
the deepening low trekking through Southern MN and thus, bringing 
higher snowfall amounts farther northward. The 17.12 ECMWF is in 
slightly better agreement with the GFS as it brings the surface 
low through the MN/IA/WI border. However, the ECMWF solution would
still bring higher snowfall amounts to Southern MN.

A ~1026 surface high and upper-level ridging will follow the mid-
week system, allowing for dry conditions on Thursday. The Western 
CONUS trough will begin to deepen and shift eastward late 
Thursday and Friday. Recent model trends indicate that split flow 
will occur once the trough exits the Rockies. The 17.00 ECMWF 
developed a surface low over the Oklahoma Panhandle that continued
to deepen as it lifted toward IL with a closed mid-level low over
the Central Plains. That would bring widespread accumulating 
snowfall into Southern MN and Central WI. However, the 17.12 ECMWF
is more in-line with the GFS by not phasing the energy from the 
northern and southern streams. Both develop a surface low further 
to the south of the 17.00 ECMWF and only bring a shortwave trough
to the Northern Plains. This would still provide an opportunity 
for accumulating snow on Saturday, but lesser amounts. Overall, 
model consensus indicates that there is near a 50% chance for over
0.25 inch liquid equivalent of snow between Friday night and 
Sunday morning. 

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1156 AM CST Sun Feb 17 2019

Light snow is as far north as it is going to make it today. Expect
a fairly steady state in conditions through 22z before snow slowly
tapers off from north to south, ending at MKT around 5z. We're
seeing good drying of the low levels across central MN and
northwest WI to the north of the snow shield and as the snow
slides south, expect the VFR conditions to drop south as well,
with VFR conditions expected across most of the area late tonight
through Monday morning. With a 1040mb high dropping in on Monday,
expect mainly clear low level skies, though GFS/NAM soundings 
showing plenty of low level moist, so can't completely rule out 
seeing MVFR cigs Monday.

KMSP...Not many changes to the going TAFs, with VFR conditions
expected to replace the snow as it slides south. GFS and NAM
forecast soundings show potential for MVFR cigs Monday afternoon,
but with a 1040mb high coming in, thinks subsidence wins out and
results in a partly cloudy, though chilly President's Day.

/OUTLOOK FOR KMSP/
Tue...Mainly VFR. Wind SW 5 kts becoming SE. 
Wed...IFR with SN. Wind E 5 kts.
Thu...MVFR cigs. Wind WSW 5 kts.


&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...Winter Weather Advisory until midnight CST tonight for 
     MNZ082>085-091>093.

     Winter Weather Advisory until 9 PM CST this evening for MNZ054-
     064-073>075.

&&

$$

SHORT TERM...MPG
LONG TERM...AMK
AVIATION...MPG