Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 091740
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1140 AM CST Tue Jan 9 2018

.UPDATE...
Issued at 1140 AM CST Tue Jan 9 2018

Updated below for 18z Aviation Discussion.

&&

.SHORT TERM...(Today through Wednesday)
Issued at 400 AM CST Tue Jan 9 2018

It`s a cold morning across most of the Northland, especially over
northern MN in the single digits below zero, thanks to clear and
calm conditions with a passing ridge of high pressure. Areas of
central and east- central MN, though, had more mild weather
overnight thanks to cloud cover. Now the rest of the Northland is
poised for more mild weather today into Wednesday. South-southeast
winds will bring warm air advection into the Northland today and
increasing moisture tonight into Wednesday. Partly to mostly sunny
skies at times today should let temperatures climb into the upper
20s and low 30s and help more of the Northland melt packed snow
and ice on roads and driveways.

There will be increasing cloud cover tonight, and the winds and
cloud cover will bolster temperatures. Lows will only be in the
middle to upper 20s. There is a low probability of freezing
drizzle and drizzle late tonight and Wednesday morning because of
subtle large-scale forcing for ascent and a decently deep low-
level saturated layer. Expect little to no accumulation.

Wednesday will be even warmer thanks to the warm start in the
morning. Despite the cloud cover, highs will range from the low to
upper 30s. The warmest conditions will be in northwest WI. Drizzle
and freezing drizzle could continue Wednesday afternoon,
especially in north-central MN where there will be the onset of
our next round of significant winter weather. More on that in the
long term discussion.

.LONG TERM...(Wednesday night through Monday)
Issued at 400 AM CST Tue Jan 9 2018

Wednesday night through Thursday the main concern remains the
winter storm that will move through the area. Synoptically, a
large upper level trough will swing out of the Rocky mountains and
out onto the plains Wednesday, with a surface boundary and and
850mb baroclinic zone draped from eastern Colorado northeast
across Minnesota and out over Lake Superior. Wednesday night a
strong shortwave swings out of the trough axis and ejects a
surface low from Kansas northeast to Wisconsin by Thursday
morning, then continuing northeast. Strong frontogenesis develops
on the northwest side of this surface low in the 850mb baroclinic
zone, producing moderate to heave precipitation that spreads into
the forecast area late Wednesday afternoon and evening, slides
southeast across the area overnight and Thursday morning before
ending during the afternoon and evening. Thermal profiles with
this storm have been difficult, with a period of mixed
precipitation expected at the onset before switching over to all
snow for the bulk of the event. The NAM and Canadian models have
been bringing the warm air farther north, with the ECMWF and GFS
colder. Expect that fairly high precipitation rates will tend to
bring temperatures down, but with differences in the temperatures,
I do not have very high confidence in the precipitation type
Wednesday evening. For now, it appears that we could have a period
of freezing rain/sleet at onset, but once the better
precipitation rates set in, a fairly fast switch over to snow
should occur. This mixed precipitation could make for very
hazardous travel conditions Wednesday evening, mainly over my
Minnesota counties. The warm temperatures retreat southeast
quickly during the evening, and expect a shorter time range of
mixed precipitation over northwest Wisconsin. Snowfall forecast
has not changed very much over the last 24 hours, and is in line
with what I was thinking two days ago, so I have increasing
confidence in the storm total snowfall amounts, with the main
uncertainty being the icing/sleet factor. With that, I have
decided to issue a winter storm watch for a majority of the
forecast area, starting earlier over northern Minnesota and ending
earlier there as well. Some areas are not approaching warning
criteria snow totals, but the mixed precipitation early on and the
later blowing snow is likely to make things seem worse. Details
will be below and in WSW.

Cold air dives into the area on the heels of the Wednesday-
Thursday storm, and the remainder of the forecast has single digit
high temperatures with lows in the teens and 20s below zero. We
are likely to need some wind chill headlines through much of the
upcoming weekend and into early next week. There are some small
chances for snow as clippers dive through the northwest flow
aloft, but no significant accumulations are in the forecast.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1140 AM CST Tue Jan 9 2018

VFR conditions will persist into this evening before ceilings
begin to lower as warm air flows north. Ceilings will lower to
MVFR and IFR during the early morning hours and then to LIFR after
sunrise Wednesday at KDLH, KINL and KHIB. There may also be some
patchy drizzle or freezing drizzle starting early Wednesday
morning. Areas of fog will be possible late tonight into early
Wednesday morning, but confidence as to where it will develop and
how low VSBYs will get preclude having it in the forecast at this
time.


&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  28  27  36  10 /   0  20  30  90
INL  30  24  33  -2 /   0  10  50  90
BRD  33  29  36   5 /   0  10  30  90
HYR  33  30  39  20 /   0  20  20  90
ASX  31  28  40  20 /   0  10  20  90

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...Winter Storm Watch from late Wednesday night through Thursday
     afternoon for WIZ001>004-006>008.

MN...Winter Storm Watch from Wednesday evening through Thursday
     morning for MNZ010>012-018>021-025-026-033>037.

     Winter Storm Watch from late Wednesday night through Thursday
     afternoon for MNZ038.

LS...None.
&&

$$

UPDATE...BJH
SHORT TERM...Grochocinski
LONG TERM...LE
AVIATION...BJH



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