Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 240105
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
805 PM CDT Sat Mar 23 2024

.KEY MESSAGES...

- Heavy snow and major travel impacts look likely area-wide
  Sunday afternoon through Monday morning. Snowfall rates of
  1-2"/hour are possible Sunday afternoon and evening,
  especially across southern Minnesota and western Wisconsin.

- Warm air is expected to advance faster and farther north into
  the area. This has resulted in some reductions to the snowfall
  forecast along and south of a line from Eau Claire, to the
  Twin Cities, and Granite Falls.

- Snow continues through Monday night for western and north-
  central Minnesota. Light snow lingers over the entire area
  through Tuesday. Gusty northwest winds late Monday night
  through Tuesday will likely lead to travel impacts from
  drifting snow across western Minnesota.

- Gradual melt expected next week as highs slowly warm back
  toward 50 by the end of the week.

&&

.DISCUSSION...
Issued at 235 PM CDT Sat Mar 23 2024

We`ve seen increasing clouds in western MN, with some light
radar returns as well. This is with some WAA/fgen around h7.
This band of forcing/moisture will continue to slowly move ENE
through the night, reaching along and northeast of the I-94
corridor by Sunday morning. This precip will be struggling to
reach the ground with a very dry sub-cloud layer in place and
this is simply a precursor to the main show to come. That main
show is associated with the jet streak you can see on water
vapor imagery moving across AZ/NM, with an attendant surface low
developing over eastern CO.

That CO low will be tracking northeast across the Plains on
Sunday, going across the southeast corner of MN Monday night,
reaching central Lake Superior Tuesday afternoon. There will be
a strong push of moisture and warm air from the south with this
low and the biggest uncertainty continues to reside around how
quickly the rain/snow line will move north across southern MN
Sunday night and where it will stall out across west central
and central MN during the day on Monday. The trend with the
forecast today was to be a bit more aggressive with bringing the
transition to rain into the region Sunday night, with the
rain/snow line getting a bit farther north and west on Monday
than the previous forecast. The greatest uncertainty in the
snowfall forecast sits from Eau Claire, to the Twin Cities, and
Granite Falls. The big question is how much QPF do we dump into
the snow bin before we transition to rain. The difference
between the 12z NAM and HRRR highlights this issue well. The
HRRR dropped 1.2" of QPF into the snow bin for MSP before
transitioning to rain around 8z Tuesday. The NAM makes the
switch to rain about 6 hours earlier and only has 0.5" of QPF
falling as snow. This would have some rather significant impacts
on the total snow seen in the Twin Cities. An early transition
like the NAM would struggle to see us get 5" of snow, while a
later transition could see totals make a run for 10+". On Monday,
we`ll see a trowal wrap into the region, which will push the
heavier precip amounts out into western MN, while a dry slot
aloft helps cut down on precip rates on Monday for eastern MN
and western WI. As the low shifts off to the northeast Monday
night, we`ll see the precip and cold air (so transition back to
snow) push east out of western MN and across central MN.

For headlines, we have replaced any watches with
warnings/advisories. We continue to run a warning out in west
central into central MN through Monday night. The main
uncertainty with the Warning was how far south to take in MN
given the rain/snow line that will be actively moving north
across southern MN Sunday night. With the potential for 2" per
hour rates right out ahead of the rain/snow line, we erred a bit
on the side of caution with the southern extent of the warning,
bringing it down to Goodhue over to Brown county. For our
southern 2 tiers of counties (Mankato/I-90 corridor), we went
with an Advisory. The other tough task was to try and hone in on
timing for the warning, trying to tie it to the transition from
snow back to rain. We have three rows of end times for the
warning at 9z Monday for south of the Twin Cities, an end time
of 12z Monday for the Twin Cities and Eau Claire, with a 15z
expiration for north of the Twin Cities and Eau Claire.

After this system, we`ll see a chilly day on Wednesday as a
surface ridge moves in. That and all the fresh snow will help
hold highs in the 20s/low 30s for Wednesday, but as the high
moves east, we`ll see warmer air move in, with highs in the
40s/50s expected to end the week. For precip, models continue to
show a good deal of run-to-run shifts with the potential for
precip and the end of the week into next weekend, but right now,
there`s be a trend to pushing any precip chances out into next
week. At this point it should be warm enough that if it does
precip, the main type should be rain.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 734 PM CDT Sat Mar 23 2024

-SN is already being reported at TAF sites in western MN so the
 event is officially underway. Though intermittent at this point
 with where the snowfall will be reported, more widespread
 snowfall will develop through this evening into the early
 morning hours for all sites, with both ceilings and
 visibilities dropping to MVFR range tonight followed by IFR
 conditions likely during the day Sunday. During the day Sunday
 will have the heaviest rates and worst flight conditions,
 including down to 1/2sm, also in conjunction with strong SE
 winds. Sustained speeds will increase to 15-20kts with gusts
 25-30kts (potentially even higher at times). So, the theme here
 is that a highly impactful system is now underway and will make
 for highly degraded flight conditions across all TAF sites.

KMSP...Have made few changes from inherited TAF, running with
-SN commencing at about 05z. The ob is reporting VIRGA and the
 KMPX radar is showing snow in the upper levels around MSP but
 not yet at the surface, so this indicates that there is some
 lower level dry air that needs to be overcome before snow is
 realized at the surface. It likely will not take long so it is
 possible some snow showers may come in an hour or so earlier
 than 05z. The more sustained snowfall is expected to start
 overnight into Sunday morning, with the heaviest rates coming
 late morning through the afternoon hours. Rates of near 1 in/hr
 are possible Sunday afternoon of heavy wet snow. The heavy snow
 will continue through Sunday evening then a rain/snow mix looks
 to develop Sunday night. Even at that point, conditions will
 likely remain in IFR category.

/OUTLOOK FOR KMSP/
MON...IFR Likely. Chance LIFR/+SN early. RA/SN mix likely
afternoon- evening. Wind ENE 15G25-30kts.
TUE...IFR/MVFR likely. Chance RA/SN mix thru afternoon. Wind NW
15G25-30kts.
WED...VFR, w/ MVFR possible. Chance -SHSN. Wind W 15G25kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...Winter Storm Warning from 10 AM Sunday to 7 AM CDT Tuesday for
     Benton-Chippewa-Douglas-Kanabec-Kandiyohi-Lac Qui Parle-
     Mille Lacs-Morrison-Pope-Stearns-Stevens-Swift-Todd-
     Yellow Medicine.
     Winter Storm Warning from 10 AM Sunday to 7 AM CDT Monday for
     Chisago-Isanti-Sherburne.
     Winter Storm Warning from 10 AM Sunday to 4 AM CDT Monday for
     Anoka-Carver-Dakota-Hennepin-Meeker-Ramsey-Scott-
     Washington-Wright.
     Winter Storm Warning from 10 AM to 10 PM CDT Sunday for Brown-
     Goodhue-Le Sueur-McLeod-Nicollet-Redwood-Renville-Rice-
     Sibley.
     Winter Weather Advisory from 10 AM to 7 PM CDT Sunday for Blue
     Earth-Faribault-Freeborn-Martin-Steele-Waseca-Watonwan.
WI...Winter Storm Warning from 10 AM Sunday to 7 AM CDT Monday for
     Barron-Chippewa-Dunn-Polk-Rusk-St. Croix.
     Winter Storm Warning from 10 AM to 10 PM CDT Sunday for Eau
     Claire-Pepin-Pierce.

&&

$$

DISCUSSION...MPG
AVIATION...JPC


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