Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 230919

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
419 AM CDT Fri Mar 23 2018

.SHORT TERM...(Today and through Saturday)
Issued at 420 AM CDT Fri Mar 23 2018

Winter Storm remains on track to bring 6 to 9 inches of snowfall
from western MN through south central MN, with a very tight gradient
along just south/west of the I-94 corridor.

Early this morning, an the first band of rain/snow has developed
across the Dakotas along the baroclinic zone currently in place
there.  We are still east of the upper ridge axis, with the
deepening trough just downstream of the ridge axis.  High level
clouds associated with the incoming system are already spilling over
the top of the ridge all the way to Wisconsin.

Not much has changed overnight in terms of expected amounts.  We did
slow down the arrival of the snow though based on the latest trends
in the Dakotas and hi-res model guidance.  This morning will begin
quiet across the forecast area.  The first band of precip, which
will start out as a mix of rain and snow, will reach far western MN
around 12-1PM but be on a diminishing trend as it lifts out of the
area. So nothing much is expected to happen until the next band of
precip associated with the ejecting low pressure area and upper
level trough/pv anomaly arrives this evening.  Hence, we pushed back
the start time of the warning in far western MN until 4PM, and the
latest guidance suggests it may need to be pushed back even farther.

From about 9PM-12AM forcing really increases across much of southern
and western MN, and a quickly expanding band of primarily snow should
develop and expand eastward.  Overnight, the 850H low will
transition south-southeast for the area, with the the snow shield
setting up parallel to the movement of the system.  Hence, the
precip will expand eastward until roughly 12-2AM, but then
transition to advancing southeast with the system.  This is why we
are confident in this system bringing a very tight snowfall gradient
with it.  Placing such a tight gradient in a forecast on the exact
location it will be is nearly impossible, and slight deviations
could mean big changes for those along the gradient.  As of right
now, the counties along I-94 will have the gradient run through
them, so Winter Weather Advisories have been posted.

Peak forcing and moisture convergence and hence heaviest snow rates
looks to occur from 9PM-6AM for southern MN, so this will generally
be the window of heaviest snow.  Travel will become difficult in the
heaviest snow bands as visibility will be significantly reduced in
snowfall rates of 1-2"/hr along with winds gusting in the 30-35 MPH

Light snow will continue into Saturday morning, but most of the
accumulation will have already occurred.  Conditions will improve
through the day, with temperatures warming above freezing by the
afternoon, aiding in cleaning up the roadways.

.LONG TERM...(Saturday night through Thursday)
Issued at 420 AM CDT Fri Mar 23 2018

An amplified pattern takes shape during the long term forecast
period as an upper level trough deepens over the southwestern
CONUS. An associated surface trough will nose into the Upper
Midwest on Monday. There is notably good model agreement that a
broad warm air/moisture advection regime will set up across the
area on Monday, as the exit region of the upper level jet supplies
prolonged forcing. Have included high (60-90 percent) precip
chances on Monday and Monday night. Thermal profiles indicate a
wintry mix of precip, although the daytime period looks to be
primarily rain as temps warm into the upper 30s and 40s across
most of the area. Model consensus for liquid QPF amounts are
generally around one half inch over central MN, and one quarter
inch from south central MN into west central WI. Snowfall
accumulations look to be minimal, and mainly restricted to the
northwest forecast area (near Alexandria), where amounts generally
around one inch or less would be the most likely scenario.

The front and forcing shift east of the area on Tuesday, while the
northern stream sags across the north central CONUS through the
week as the aforementioned southwest trough dips across Texas.
Weak blips of mid-level shortwave energy pass across the area
periodically during the remainder of the week, but appear
relatively insignificant at this point. Have therefore maintained
a mostly dry forecast from Tuesday through Thursday, with
temperatures fairly close to normal for late March. Highs in the
40-50 degree range will be common, with lows generally from 25-35


.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1119 PM CDT Thu Mar 22 2018

Mid level cloud deck across southern MN is slowly sagging south
this evening. High clouds Friday morning will thicken and lower to
a mid level deck again by Friday afternoon. Further lowering will
occur, with snow moving into western Minnesota mid to late
afternoon, spreading east to the Mississippi River late Friday
evening. Occasional heavy snow is most likely at AXN, RWF, MKT
Friday evening. East winds will increase and could gust to 30-35
kt by afternoon.

KMSP...No concerns until later Friday evening when snow begins to
move in. Cigs and visibilities will deteriorate after 04-05Z

SAT...MVFR with morning -SN. Wind E 10-15 kts.
SUN...VFR. Wind SE 10-15 kts.
MON...MVFR with -RASN, possibly IFR. Wind SE 5-10 kts.


MN...Winter Storm Warning from 8 PM this evening to 10 AM CDT
     Saturday for MNZ058-066-067-075-076-083>085-092-093.

     Winter Storm Warning from 4 PM this afternoon to 10 AM CDT
     Saturday for MNZ041-047-048-055>057-065-073-074-082-091.

     Winter Storm Warning from 11 PM this evening to 10 AM CDT
     Saturday for MNZ068-069-077.

     Winter Storm Watch from this evening through Saturday morning
     for MNZ049.

     Winter Storm Watch from this evening through Saturday morning
     for MNZ059-060-070-078.

     Winter Storm Warning from 1 PM this afternoon to 10 AM CDT
     Saturday for MNZ054-064.

     Winter Weather Advisory from 8 PM this evening to 10 AM CDT
     Saturday for MNZ042.



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