Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 261120
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
520 AM CST Sun Feb 26 2017

.updated for the 12z aviation discussion below...

.SHORT TERM...(Today and tonight)
Issued at 343 AM CST Sun Feb 26 2017

The main short term concern is chance of light snow across
northern cwa into the afternoon.

Light snow developed over central Minnesota last evening and did
drop an inch or two of snow over the far north cwa. It
fizzled/lifted farther north as it moved slowly east. This
all associated with weak waa/isentropic lift along the upper
trough which will redevelop into the same area this morning. Radar
trends show a band of light snow/snow showers moving into west
central Minnesota at this time.  This should spread east as the
upper trough and surface cold front move in during the morning.
Timing would bring it to east central Minnesota 15z-18z. We
expect any accumulation to be light, generally a dusting to an
inch into northern cwa. High temperatures will remain at or below
freezing in snow covered area, with some mid 30s possible over
central Minnesota as some sun should develop as the front moves
through.

The front sags into southern Minnesota by this evening and may
stall/move slowly north later tonight.  Some patchy fog may
develop, mainly over snow covered areas in the south after
midnight, with light winds and some radiational affects possible.

.LONG TERM...(Monday through Saturday)
Issued at 343 AM CST Sun Feb 26 2017

The main issue in the long term still revolves around precip chances
and types Monday night/Tuesday. The rest of the period looks to only
offer minimal precip chances, with a brief cool down Wednesday and
Thursday before we look to go significantly warmer again Friday and
Saturday.

This Monday night/Tuesday system continues to be problematic in
terms of precip placement and coverage. There will be a couple of
sources of lift for precip. One will be isentropic lift and theta-e
advection with the LLJ Monday night and the other f-gen along the
boundary that stalls out over MN Monday. The vast majority of the
precip with the WAA Monday night looks to stay off to our southeast,
with thunderstorms expected to fire up across IA into southern
WI/northern IL as unstable air surges north out of the central
Plains. This thunderstorm activity should limit the amount of
moisture we can get up this direction Monday night, with maybe a
couple of hundredths of an inch of QPF sneaking into our southeast
CWA. There is the drizzle potential with this activity Monday
night/Tuesday morning, but forecast soundings do not show much omega
within the moist low-levels, so don`t know if we will get much of
that either.  Tuesday afternoon and evening, the approach of a
strong shortwave in the southwest flow out of WY will allow the
stalled out frontal boundary to become active, with a deformation
band of snow developing on the cool side of the boundary.
Increasingly, this looks to occur from central MN up toward Lake
Superior.

For P-type, that looks to be closely tied to surface temperatures.
Here, we warmed them to be near CONSRAW values, with MOS numbers
looking too cold, especially with lows Monday night.  This keeps
areas that have a melting layer aloft above freezing at the surface
to keep the type as rain, which nicely cut down on the amount of
sleet/freezing rain mention and also gets the forecast in line with
what forecast soundings from the NAM/GFS would say for p-type Monday
night into Tuesday morning. For the afternoon/evening activity up in
central MN, CAA on the cold side of the front will keep this
deformation precip as mainly snow, with the potential for a couple
of inches of snow there before the snow moves out Tuesday night.

Of course Tuesday will mark the end of February and it is looking
unlikely St. Cloud or MSP will be getting any more snow, which would
mean both locations would finish the month of February with just 0.3
inches of snow. There has been one February in the Twin Cities with
no snow (1891) and two in St. Cloud (1921 and 1894), so this will
not go down as the least snowiest February on record. However,
this will be only the 4th time the Twin Cities has seen less than an
inch in February and the 8th time for St. Cloud.

For Wednesday and Thursday, we keep sporadic precip mentions going.
This is because the trough that builds into the Rockies on Monday
does not clear off to our east until Thursday night. Wednesday`s
precip chances are tied to the possibility of light precip
persisting along an inverted surface trough, while Thursday`s
chances are driven by a strong wave dropping down out of Canada. In
both cases, precip amounts, if we see any, look minimal. What these
successive waves will do is bring progressively colder air south,
which looks to culminate in our coldest period Thursday and Thursday
night, when highs will struggle for 30 followed by lows in the
single digits and teens.

We will quickly snap out of the cold weather on Friday as ridging
moves across central North America and strong southerly return flow
develops. By Saturday, the passage of a surface low across southern
Canada will draw unseasonably mild air back north, with highs back
into the 50s certainly looking possible Saturday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 520 AM CST Sun Feb 26 2017

MVFR or lower ceilings and visibilities expected to develop and
spread est with the front this morning. Should develop into
western Wisconsin as well. Expect a period of -sn affecting
KAXN/KSTC and possibly KMSPand KRNH. Confidence not as high of the
area dropping this far south...so continued the vcsh trend. VFR
cigs developing through the afternoon and continuing into tonight.
Winds becoming w-nw with fropa and gusty for a few hours. SHould
become light and variable or light se overnight.

KMSP...Confidence increasing for at least a few hours of MVFR cigs
with fropa...roughly 14z-18z period. Also continued to mention the
vcsh...confidence not high enough to include at this time. Should
return to vfr this afternoon and remain through the rest of the
period. SW wind becoming NW with fropa and eventually light se
overnight.

/OUTLOOK FOR KMSP/
Mon nite...MVFR. Chance -RASN Mon night. Wind S 5-10 kts.
Tue...MVFR likely. Chance -RASN. Winds E 5 kts shifting to N.
Wed...MVFR ceilings possible. Otherwise VFR. Winds N 5-10 kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&

$$

SHORT TERM...DWE
LONG TERM...MPG
AVIATION...DWE


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