Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 160815

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

.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 00Z TAFS through 00Z Friday evening)
Issued at 951 PM CDT Thu Mar 15 2018

No changes from 00z TAFs. Dry east winds will keep skies VFR and
any precip southwest of all MPX terminals through the course of
the 6z TAF period. Also continued to advertise wind speeds a bit
above guidance for during the day Friday 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 cigs. Wind vrb 5 kts or less.
MON...Chc MVFR cigs. 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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