Area Forecast Discussion

FXUS63 KMPX 222059
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
359 PM CDT Thu Mar 22 2018
.SHORT TERM...(This evening through Friday)
Issued at 345 PM CDT Thu Mar 22 2018
The forecast has not changed too much for tonight, and into Friday
afternoon. However, the onset of the precipitation has been
delayed a few hours in eastern Minnesota. Temperatures tonight
will drop fast, then level off once cloud cover begins to build
across the west. Friday temperatures will reflect the change over,
or how quickly the change over to snow occurs. Currently highs
will likely be Friday morning in western Minnesota, before the
precipitation gets heavier. In the east, temperatures will rise to
near 40 before precipitation starts to develop. 
.LONG TERM...(Friday night through Thursday)
Issued at 400 PM CDT Thu Mar 22 2018
The main event will occur late Friday. 
First, a very strong late Winter, early Spring storm will be 
developing late tonight in the Dakotas, and move east, southeast 
across the Minnesota, and far west central Wisconsin through 
Saturday afternoon. 
Timing, amounts and associated impacts are the main concerns over 
the next 24-36 hours. 
Second, there will be a strong gradient where the heavy snow 
falls, and where little snow occurs on the northeast side of the 
storm track. This tight gradient has been discussed over the past 
day or so and no question that this gradient will occur. The main 
question is where does this gradient occur? Due to the proximity
of where this tight gradient will occur is also a great concern.
At this time, the tight gradient will occur over the Twin Cities 
Metro area. Impacts will occur, especially for those traveling to
south and west of the cities. Therefore, please continue to 
monitor the forecast as some deviation will occur as the storm 
Based on the latest information, the eastern side of the Twin 
Cities may only receive a dusting, where the western side of the 
cities, could receive up to a foot of snow. The main timing will
be 9 pm Friday night, through 9 am Saturday morning.
Although confidence has increased enough to issued winter storm 
warnings for portion of west central Minnesota, there is still 
the uncertainty to the south and east. Even a slight drift to the
southwest or northeast will greatly impact a very small area of 
Minnesota. Therefore, a winter storm watch continues for the
remainder of central and southern Minnesota. The highest 
confidence of receiving more than 6 inches of snowfall for this 
event will be along a line from Morris in west central Minnesota, 
southeast to Willmar, Gaylord, and Owatonna Minnesota. 
One item to note, most of the short term ensemble members (snowfall
parameters) have shown a southwestern drift of the highest 
snowfall totals across Minnesota. This is mainly due to the drier
and stronger northeast/easterly winds advecting into this storm. 
Thirdly, some timing changes are noted, especially due to the 
drier air initially. This will aid in drying the lower atmosphere 
on the eastern edge of the precipitation field, or commonly 
referred to as virga. But, once the precipitation develops, expect
a long duration of snow (6-12 hours), with heavy snow likely 
Friday evening in west central/southwest Minnesota, and this area 
slowly pivoting to the southeast across south central Minnesota 
early Saturday morning. Thermal profiles across southwest, south 
central Minnesota are warm enough for more sleet or rain during 
the onset of the precipitation Friday morning/afternoon. If more 
rain/sleet occurs, snowfall amounts could be significantly reduced
on the southwest side of the storm system. This area where more 
rain/sleet occurs is mainly south and west of the Minnesota River 
This system will quickly dissipate Saturday by noon, with some 
clearing possible Saturday afternoon, especially in western 
Minnesota. Due to the strong and higher sun angle for late March, 
any snow that fall will likely melt in a few days. 
Not much to say in the extended period, or after Friday/Saturday 
storm, as the next system will be much warmer, and most of the 
precipitation will be in the form of rain vs. snow. This may
become a concern as melting of snow from this system, plus the 
added precipitation for late Sunday/Monday system, could produce 
localized flooding. This is especially a concern along smaller 
creeks and streams. This is due to the frozen ground, deep frost 
layer, and the quick runoff from the precipitation. 
After Sunday/Monday system, the flow becomes more northwest, which 
means cooler but drier. Winter continues to hold on... 
.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1215 PM CDT Thu Mar 22 2018
Calm before the storm... Through 18z Friday, most areas will 
remain VFR with the light snow developing this TAF period. Only 
far southwest/west central Minnesota will see lower vsbys/cigs 
before 18z. Winds will remain light through this afternoon/evening
before increasing overnight with gusts of 20-26 kts in 
western/southern Minnesota by late morning from the east. 
No additional concerns through 18z Friday. After 18z, winds will
remain from the east, but gusts could approach or exceed 26 kts 
during the afternoon. Light snow and MVFR cigs will hold off until
after 00z Saturday. 
Late FRI...MVFR/IFR cigs/vsbys with -SN, possibly SN/+SN. Wind E 15G25kts.
SAT...MVFR with a.m. -RA/-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 4 PM Friday to 10 AM CDT Saturday for 
     Winter Storm Watch from Friday evening through Saturday morning 
     for MNZ049-058>060-066-068>070-076>078-085.
     Winter Storm Watch from Friday afternoon through Saturday 
     morning for MNZ057-065-067-074-075-082>084-091>093.
     Winter Storm Warning from 11 AM Friday to 10 AM CDT Saturday for 
     Winter Storm Watch from Friday morning through Saturday morning 
     for MNZ073.