Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 010021
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
721 PM CDT Sun Apr 30 2017

.SHORT TERM...(This evening through Monday)
Issued at 340 PM CDT Sun Apr 30 2017

The main forecast concern is when and how heavy the precipitation
becomes later tonight as a large/strong storm system moves from
the Central Plains, northeast across the Upper Midwest.

Similar snowfall ratios are expected with this system with an
average of 6-1 to 8-1. These ratios are fairly close to the previous
forecast with snowfall totals by Monday afternoon/evening ranging
from 3 to 5 inches from Canby/Montevideo, northeast to Sauk
Centre, and Little Falls. There could be localized amounts of 5 to
7 inches if snowfall intensity increases due to elevated
instability.

Forecast soundings have indicated that the atmospheric column will
cool overnight in southwest, west central and central Minnesota
where surface temperatures will fall to near freezing. The
contrast from west central Minnesota, to east central Minnesota
is rather sharp in terms of the depth of the warm layer aloft,
especially after midnight. Forecasters need to look for cooling
cloud tops, atmospheric warm conveyor belts /Water Vapor Imagery/,
and correlate them to regional radar to see if banding develops.
This could indicate increasing snowfall amounts and will bring
snowfall totals much higher than expected.

How far east this cooling atmospheric column develops will
determine whether snow develops Monday morning in east central
Minnesota. EC/GFS/GEM all have some light snow Monday
morning/afternoon as colder air arrives in eastern Minnesota, but
will surface temperatures be cold enough for the snow to reach the
surface? The best forecast is to hold onto a mixture of snow in
east central Minnesota by Monday morning, but no accumulation.

.LONG TERM...(Monday night through Sunday)
Issued at 340 PM CDT Sun Apr 30 2017

The latter portion of the forecast is quite quiet for a change.
Overall, we will see the upper trough shift eastward through the
week as an upper ridge builds into the center of the country. This
means we`ll see moderating temperatures from midweek onward with
things getting back to near or above where they should be for this
time of year. There are some differences in the individual
solutions, but general agreement on the overall evolution of things,
so stuck closer to a consensus blend of the available guidance. We
will still have some precipitation on the backside of the current
system lingering over the area tomorrow night, with some rain and
snow showers, but little if any additional snow accumulation over
the area. We will get onto the backside of the large scale upper
trough Wednesday, but a shortwave trough descending down its back
side could bring some showers to the area Wednesday into Thursday as
an associated surface trough moves through the region. This should
push east on Thursday as warmer and drier air begins to surge in
from the west. Things then look to be mild, fair, and dry through
the remainder of the period. The only potential item could be some
showers on Friday night into early Saturday across the east as a
southeastward moving northern stream wave drops by to our east.
However, at this point most of the guidance keeps that feature to
our east and probabilities in the GEFS for any measurable
precipitation remain quite low for our area.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 721 PM CDT Sun Apr 30 2017

VFR conditions still existed early this evening from west central
MN to the MSDP metro and into Wisc, with MVFR farther south in
Minnesota and IFR in areas of northwest Iowa. Ceilings will lower
this evening as precip spreads and develops northward. Winds will
also remain from the northeast at 13-18 kts sustained for much of
the night, with the only exception being diminishing wind in
southeast MN and Wisconsin on Monday when surface low moves in. A
transition to northerly winds is also expected as low moves into
southeast MN. Finally, snow will begin to mix with and change
over across west central Minnesota late this evening, and across
central Minnesota overnight. Snow is expected to change back to
light rain midday Monday as lift begins to wane.

KMSP...

MVFR and eventually IFR conditions will move into KMSP later this
evening when steadier rainfall arrives ahead of surface low. Other
issue is persistent northeast wind remaining at 13-18 knots with
gusts over 25 knots this evening. Northeast gusts will weaken
slightly late tonight and Monday morning as surface low approaches
southeast MN, but still expect gusts around 20 knots through 12Z
Monday. The good news is that by late Monday morning, probably
around 15Z, wind direction should be more around 360 with
approach of surface low. Some snow could mix in around dawn but
it is not expected to last long nor accumulate.

/OUTLOOK FOR KMSP/

Tue...MVFR with VFR possible late. Wind NW at 10G15kt.
Wed...VFR with MVFR possible. Chc -ra. Wind SE at 5-10kt.
Thu...VFR with MVFR possible. Chc -ra. Wind NW at 5-10kt.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...Winter Weather Advisory from 10 PM this evening to noon CDT
     Monday for MNZ041>045-047>050-054>057-064.

&&

$$

SHORT TERM...JLT
LONG TERM...
AVIATION...TDK


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