Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 161038

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
538 AM CDT Fri Mar 16 2018

Issued at 518 AM CDT Fri Mar 16 2018

Updated to include 12z aviation discussion below.


.SHORT TERM...(Today and tonight)
Issued at 300 AM CDT Fri Mar 16 2018

Surface analysis early this morning shows high pressure centered
over the MN international border, extending south into central
IL/IN. Meanwhile. a potent low pressure system continues to
develop over the lee of the Rockies, centered over the CO/KS
border with a warm front extending eastward into southern MO and a
cold front extending S through the TX/OK panhandles. Aloft, a
sharp ridge axis from central Saskatchewan province extends SSE
into the mid- Mississippi River valley while a cutoff low sits
atop the surface low over CO/KS and more extensive trough features
exist over the east coast and west coast.

Over the next 24 hours, the ridge aloft and surface high pressure
features will remain rather stout and this will keep the bulk of
the low pressure system to the south of MN/WI while it slowly
shifts east. As such, the bulk of the moisture will remain tightly
confined to the stacked low pressure system, with clouds
increasing over southwest MN today but mainly remaining south of
the MN River in western MN. Multiple short-term models continue to
indicate the development of rain/snow over southwestern MN which
looks to spread into the lower 2 tiers of counties in southern MN
this evening through the overnight hours. while a modest warm
layer aloft moves into far southern MN while surface temps drop,
though the bulk of the precip will change over to snow after dark,
there will be some pockets of freezing rain within the
precipitation, particularly over southwestern MN. Small amounts of
icing look to develop over the I- 90 corridor in southwestern MN
along with snowfall up to around an inch. Given the consistent
signal through this forecast run, and the potential for close to a
tenth of an inch of ice accumulation in Martin County MN, have
opted to issue a Winter Wx Advy for that sole county in southern
MN (in collaboration with WFOs DMX and FSD).

As the low pressure system slides east across KS and MO through
overnight tonight, the system will become further stacked and fill,
thus weakening the system and allowing precipitation to diminish. By
daybreak Saturday morning, no further precipitation is expected.

Meanwhile, throughout the entire duration of this system, north of
a line from roughly Morris-Litchfield-Bloomington-Red Wing will
have mostly clear skies.

.LONG TERM...(Saturday through Thursday)
Issued at 300 AM CDT Fri Mar 16 2018

A couple of concerns in the longer term. The timing of the Monday
night through Wednesday trough and attendant precipitation. The
other issue being the next chance for precipitation coming late in
the week.

Initially, we should see precipitation move out of southern
central MN around 12z Saturday. Low level flow favors remaining
clouds shifting slowly westward during the day. Most models
suggest lower clouds to remain locked under the relatively weak
flow/ridging aloft. We will trend a little cloudier for Sunday and
this will likely affect temperatures. Saturday could be the
warmest, with afternoon readings warming the 40s. Sunday could be
a degree or two cooler.

Models have slowed the next incoming trough, which should hold
off until at least Monday night. It will likely linger through
Tuesday night however, with both deterministic long range models
showing the trough split with most of the energy/moisture riding
south of the area. We have a lingering northern stream trough
moving through Tuesday/Tuesday night which will bring a possible
rain/snow mix.

Temperatures warm then through the end of the week as ridging
aloft ensues once again. Timing of the next trough by both the
GFS and ECMWF brings in a rain/snow mix next Friday. Models
diverge on overall evolution of this trough with the GFS most
amplified and developing a closed low. The ECMWF is more
progressive, which would move precipitation out quicker next


.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 518 AM CDT Fri Mar 16 2018

Very few changes from 06z TAFs. Dry east winds will keep skies
VFR and any precip southwest of all MPX terminals through the
course of the 12z TAF period. Small chance a few rain/snow showers
could make it as far north as KMKT this evening so have added VCSH
but am expecting very minimal impact, if any precipitation
reaches there at all. Also continued to advertise wind speeds a
bit above guidance for during the day based on what we saw
Thursday and mix down potential from GFS/NAM forecast soundings.

KMSP...No additional concerns.

SAT...VFR. Wind E 5 kts becoming S.
SUN...Chc MVFR ceilings. Wind VRBL 5 kts or less.
MON...Chc MVFR ceilings. Wind ENE 5-10 kts.


MN...Winter Weather Advisory from 7 PM this evening to 7 AM CDT
     Saturday for MNZ091.



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