Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 210918

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
418 AM CDT Wed Mar 21 2018

.SHORT TERM...(Today and tonight)
Issued at 417 AM CDT Wed Mar 21 2018

Short term concerns are clouds and any precipitation this morning.

Water vapor imagery showing upper trough moving through central MN
at this time. Enough lift/moisture with this to generate some
flurries at this time. Will continue this trend to the east a
little farther before we should see forcing weaken further and run
into drier air to the east. We do see movement of S-SE about
15kts to the radar echoes and this will move into at least the
west metro this morning. Only anticipate flurries at this time.
Lower clouds are beginning to shift more southeast as well, but is
quite slow with some erosion continuing on the eastern flank.
Will try and time this into western Wisconsin by late morning. A
secondary trough is moving through central North Dakota at this
time. Mosaic radar is showing some echoes moving through eastern
North Dakota and currently expect main forcing will work into
northern MN during the day. High temperatures will remain tempered
by the clouds expected today with highs generally 35 to 40.

Expect clouds to continue tonight over much of the area, gradually
shifting a little more north overnight. Lows should remain in the
mid/upper 20s over the cloudy areas, perhaps dropping into the
upper teens again where clouds are thinnest, mainly over west
central WI.

.LONG TERM...(Thursday through Tuesday)
Issued at 417 AM CDT Wed Mar 21 2018

After a dry day on Thursday with high pressure sliding over and
away from the area, models are still on track to indicate the
development of precipitation starting during the day on Friday. A
low pressure center emanating from the northern Rockies looks to
shift southeast through the Central Plains during the day Friday
along a leading edge frontal boundary. Aloft, moisture will merge
from the Pacific and Gulf source regions while isentropic lift is
heightened in advance of the low. Precipitation then looks to
overspread the entire coverage area Friday night through much of
Saturday before diminishing late day Saturday into Saturday
evening. While there is still high confidence in the occurrence of
precipitation for the late Friday through Saturday period, there
is still much uncertainty with respect to the precipitation-type
and timing of any changeovers. Models now indicate a slightly
cooler solution but also the potential for a dry lower layer
Friday night into Saturday morning. This would indicate a slightly
snowier solution but also the potential for freezing rain.
However, the dry layer solution is mainly brought about by the GFS
and is a relatively new entry into an already tricky forecast
solution. Given this difference, have opted to stay the course of
only advertising rain/snow with this event. In addition, QPFs look
to have quite the range from east to west across the WFO MPX
coverage area through this event. The bulk of west-central WI may
only see up to a tenth of an inch (possibly up to a quarter inch
near the KRGK area) while western and southern MN are likely to
receive between 0.50"-0.75", if not more. Given the transition to
-SN Friday night, this would produce a few inches of wet heavy
snow before changing back to rain during the day on Saturday as
the center of the system moves through the Mid- Mississippi River
Valley into the southeastern CONUS. The sharp delineation in QPF
looks to occur roughly along a Long Prairie-St Cloud-Twin Cities-
Red Wing line with the higher amounts to the west and lesser
amounts to the east. The amount of cold air entrained into the
system will also play a part, and this is evidenced by slightly
dropping max temps on Friday from previous model runs. Yet, should
the low level dry layer come to fruition, this would delay
saturation aloft and produce more FZRA than currently anticipated.
Thus, there are still many moving parts to this system that need
to be resolved before saying with any high degree of confidence
how much snow and/or ice may occur.

Then, once this system moves off to the east Sunday, another low
pressure system of a traditional Panhandle Hook variety looks to
develop on Monday and shift northeast into the Great Lakes through
Wednesday. This system also looks to bring a mixture of wintry
precipitation to the region, mainly Sunday night through Monday
night. Again, still plenty of uncertainty abounds with this system
with regards to details so there is still a lot of resolving to
do over the next several days.

The good news - models do indicate a warming trend for the middle
portion of next week which may bring upper 40s to near 50 degree
highs to the area.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 954 PM CDT Tue Mar 20 2018

MVFR conditions will prevail into Wednesday at most MN sites,
with IFR ceilings possible at times overnight at western sites
(KAXN and KRWF). Improvement will be slow on Wednesday, with MN
sites likely to experience MVFR ceilings through much of the day.
Light and variable to southeast winds gradually become southerly
on Wednesday, but speeds will be light overall(generally around
5 knots).

KMSP...KMSP will be on the edge of MVFR ceilings, but expect the
potential to increase during the overnight hours. Would expect
them to stay above 1800 feet however.

THU...VFR. Wind ENE 5 kts.
FRI...VFR early becoming MFVR with -RA/-SN. Wind ESE 10G15
SAT...MVFR with Chc -RA/-SN. Wind ESE 10G15 kts.




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