Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 161803
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
103 PM CDT Mon Apr 16 2018

.Updated for 18Z Aviation Discussion...
Issued at 1255 PM CDT Mon Apr 16 2018

&&

.SHORT TERM...(Today and tonight)
Issued at 330 AM CDT Mon Apr 16 2018

The main concern in the short term is clearing trend and light
snow threat early.

Water vapor imagery showing well defined vorticity maxima rotating
around upper circulation over east central MN this morning. Enough
lift and remaining moisture to continue to generate some light
snow/flurries over the southeast. Still have moisture wrapping
around the circulation over northeast MN and some of that moisture
continues to spill to the southwest over the remainder of eastern
MN. Looks to be mainly flurries, but still could see a weaker
snowband develop into the early morning. Dont expect any
significant accumulation however. Clouds are expected to remain
over the eastern areas today, under the cyclonic flow and CAA. May
see a few breaks early but those are expected to fill in this
morning. Some clearing expected to the west into the afternoon,
and then eventually east into the evening. Clouds along with the
deep fresh snowpack will hold temperatures in the low to mid 30s.
Could see a 40 to the far west with clearing into the afternoon.
The surface ridge builds slowly east across the area during the
night providing mainly clear sky and temperatures in the upper
teens to low 20s.

.LONG TERM...(Tuesday through Sunday)
Issued at 330 AM CDT Mon Apr 16 2018

Tuesday through Wednesday Night...Focus remains on this portion of
the forecast as additional snow accumulations look more likely,
particularly for southern MN. Residual high pressure and a sharp
ridge axis will be in place for the start of and most of Tuesday,
continuing to shift east across the area. However, a longwave
trough axis will swing across the Rockies during the day on
Tuesday, helping develop an area of low pressure over eastern WY.
The low is expected to track to near Kansas City by midnight
Tuesday night then to eastern IA by daybreak Wednesday morning and
continuing to southern MI by Wednesday evening. This track,
south of MN/WI, along with cold temperatures in place not only
synoptically but aided by the existing snow pack and also plenty
of Pacific moisture accompanying this system, will help promote
wintry weather development over much of the area, especially in
southern MN. A large lobe of PV will quickly slide southeast from
western Canada, keeping the trough in a negative tilt as it nudges
the surface low to the east. This will aid in rather efficient
precipitation generation starting late Tuesday night through
Wednesday morning. While there looks to be some mixture of p-types
in this system, the prevailing p-type will be a high-moisture-
content snowfall. QPFs over southern MN will rise to around 0.75"
which will likely translate to 5-8" of snow in the southern 2
tiers of counties in the WFO MPX coverage area, dropping to around
2" of new snow accumulation in central MN, including the Twin
Cities metro. Have gone slightly colder than guidance given the
impressive snow cover in place, and this will impact the amount of
snow expected for the area, and latent heat release may also
contribute to this system by keeping surface temperatures possibly
more steady than currently advertised during the day Wednesday and
also by enhancing precipitation intensity. Considering WPC and
some guidance contains snow accumulation totals as high as 10" in
far southern MN, there still may well be some adjusting to the
snow totals. Nevertheless, confidence is high enough at this point
to issue a Winter Storm Watch for the southern 2 tiers of counties
in the WFO MPX coverage area. The precipitation is expected to
diminish Wednesday evening as the system pulls away with no
additional precipitation expected going into Thursday morning.

Thursday through Sunday...Once past this next wintry system,
extensive high pressure looks to dominate over the Upper
Mississippi River Valley through the Great Lakes for the end of
this week through the week. The high pressure looks to suppress to
the south another area of low pressure developing over CO Friday,
sending it into the Deep South over the weekend while another low
pressure system remains well to the north in central Canada. The
silver lining here, besides the dry weather expected for several
days, is an increase in temperatures. Blended model guidance tries
to push the area into the lower 50s for the weekend. However, this
will be dependent on the snow cover across the area. It could be
that guidance may be a few degrees warm, making mid-to-upper 40s
potentially more realistic. Either way, more daily sunshine
combined with temperatures well above freezing will aid in
steadily reducing the snow cover across the area going into the
3rd week of April.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1255 PM CDT Mon Apr 16 2018

MVFR conditions possible for the first few hours this afternoon,
but should see VFR conditions throughout tonight into Tuesday as
high pressure builds across the region. Skies should clear
overnight and northwest winds will become easterly on Tuesday.

KMSP...
Cloud bases should remain above 3000ft today so expect VFR
conditions throughout. Clouds will dissipate tonight and northwest
winds will become easterly on Tuesday.

/OUTLOOK FOR KMSP/
Wed...MVFR with IFR/SN possible 12Z-21Z. Wind NE 5-10 kts
becoming NW.
Thu...MVFR. Wind NW at 10 kts.
Fri...MVFR. Wind SW at 5-10 kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...Winter Storm Watch from late Tuesday night through late
     Wednesday night for MNZ082>085-091>093.

&&

$$

SHORT TERM...DWE
LONG TERM...JPC
AVIATION...JRB



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