Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 161413
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
913 AM CDT Thu Mar 16 2017

.UPDATE...
Issued at 913 AM CDT Thu Mar 16 2017

A mainly clear sky this morning, except for a patch of clouds
along the St. Croix river valley into northwest Wisconsin. Expect
this patch of clouds to dissolve as the atmosphere is very dry and
mixing occurs. Still expecting an increase in mid and high clouds
from west to east today. Have adjusted sky grids accordingly.
Slowed the onset of the precipitation to later this afternoon as
the atmosphere needs to moisten exponentially first. This is in
line with latest short term hires models RAP/HRRR/NARRE. Made some
other minor tweaks as well.

&&

.SHORT TERM...(Today through Friday)
Issued at 418 AM CDT Thu Mar 16 2017

The forecast for late this afternoon and early Friday remains
challenging, and the focus of the forecast. The models are still
indicating a band of pcpn will move through the Northland,
bringing at least rain and snow, and possibly freezing rain and
drizzle. There are still notable differences in the models in the
timing and amount of precipitation, which particularly makes the
forecast for snowfall challenging. Overall, think there is now a
greater concern for snowfall with this system, compared to the
threat of freezing rain and snow. Confidence in up to several
inches of snowfall, for the Minnesota Arrowhead, Iron Range, and
parts of the Borderland to justify a winter weather advisory,
which would also cover the threat of freezing rain and drizzle for
that area. May need to add additional advisories, more for the
freezing rain/drizzle threat, with subsequent forecasts, but
confidence is not as high for other parts of the forecast area to
justify an advisory at this time.

Today...A surface ridge over the western Great Lakes, as of early
this morning, will continue to shift east through the Great Lakes,
while a surface low will be moving east across Saskatchewan.
Southerly flow will develop across the Northland and usher in
warmer and more humid air. Breezy conditions will develop across
much of the Northland. Increasing cloud cover from the west, in
association with the low pressure approaching from the west, will
tamper should tamper down the potential for high temperatures
today. Highs will be in the upper 30s to low 40s for most areas.

Late Today through early Friday...A light to moderate
precipitation band, along and ahead of the Canadian low`s
elevated warm front, is expected to develop and move through the
Northland, bringing the threat of multiple precipitation types.
The combination of saturated isentropic lift and increasing large-
scale lift from decreasing heights from the west, will result in
deepening saturation aloft ahead of the warm front, and
precipitation eventually reaching the ground by this evening.
There are still model differences in the timing and strength of
the precipitation, with the drier/slower models perhaps doing
better at reflecting how it will take some time to saturate the
relatively dry air. It should be cold enough aloft to confidently
produce snow, but the potential for it reaching the ground will at
first be hindered by potential melting from a slightly warm layer
aloft, as well as surface temperatures in the 30s and the dry
surface layer. However, the snow will likely come down hard enough
to relatively quickly drop the surface temperatures in the late
afternoon and early evening, and begin resulting in snowfall
accumulation this evening as surface temperatures drop into the
low 30s overnight. There will likely be good lift in the dendritic
growth zone, too, which will promote a quick burst of snowfall
from large flakes, especially over northern Minnesota. The
snowfall forecast is now much, much higher than before, with
accumulations of 3 to 5 inches across much of the Minnesota
Arrowhead, Iron Range, and north of the Range. Other areas, like
northwest Wisconsin, the Twin Ports, and International Falls, are
forecast about 1 to 2 inches. There is also a freezing
rain/drizzle threat tonight, mainly on the tail end of the
precipitation band when the air dries aloft and cuts of the
seeding of ice crystals in the saturated layer below. Think icing
will be light, so only have minimal accumulations for some areas.
This threat is more tricky to forecast and will need to be
revisited by the subsequent shift. If confidence increases enough
in icing accumulation, then we might need to add more winter
weather advisories.

Friday afternoon...The low in Canada will move through northwest
Ontario, and its upper trough will move over the Northland. The
cool west-northwest flow and large-scale lift will promote
widespread cumulus and the threat of convective rain and snow
showers. Gusty winds are expected, too. Highs are forecast to be
in the upper 30s and low 40s.

.LONG TERM...(Friday night through Wednesday)
Issued at 418 AM CDT Thu Mar 16 2017

Progressive pattern through the long term period with
temperatures generally near normal in the 30s and 40s - mild this
weekend then cooler next week. A few chances for precipitation
through the longer term period...light snow showers Friday night
as a low exits, light rain/snow late Sunday associated with a cold
front passage, then dry early next week before a wet pattern sets
up for the second half of next week. Possibly windy Monday in the
wake of the cold front passage, but generally no widespread high-
impact weather anticipated.

On the synoptic scale a low wil be exiting the upper Great Lakes
Friday night into Saturday with high pressure building over
northwest Ontario, extending southward across the mid and upper
Mississippi River Valley. High pressure building in will result in
a sunny and seasonable Saturday with highs in the 30s to low 40s.

Late Saturday into Sunday a warm front lifts northeast across the
upper Midwest associated with a surface low in northern
Saskatchewan moving east into northern Manitoba. Warmer air will
be advected in out of the southwest with breezy winds gusting to
around 20 mph. Highs in the upper 40s to low 50s for areas with
little to no snow on the ground, but cooler across the Minnesota
Arrowhead where a decent snow pack remains. Increasing clouds
Saturday night into Sunday, with an increasing chance for rain
changing to snow Sunday into Sunday night. Amounts will be light
because while large- scale forcing driven by the warm air
advection should be decent enough to produce light rain/drizzle,
the best lift associated with the low will be too far north into
Canada. Best chance for precipitation will be when the cold front
associated with this low crosses from west to east across northern
Minnesota Sunday night with light snow possible - less than an
inch.

Dry northwest flow Monday and Tuesday, with windy conditions
possible Monday as sunny skies lead to deep mixing up to around
850mb, causing sustain winds of 15 to 20 mph and gusts up to 35
mph. Highs in the 40s Monday, cooler in the 30s Tuesday. Lows
falling to near zero along the international border Tuesday night
as high pressure builds across northwest Ontario.

A pattern change mid to late weak as a mid-level longwave ridge
across the central states and a deepening longwave trough across
the west coast lead to a period of southwesterly flow for the
Great Plains. This would typically lead to a period of wet weather
depending on the evolution of a surface low as mid-level
shortwave troughs eject out of the Rockies into the Great Plains.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 647 AM CDT Thu Mar 16 2017

VFR conditions today will rapidly deteriorate towards this evening
as a band of wintry precipitation moves from west to east across
the region. Precipitation type will likely change between rain,
sleet, snow, and freezing rain at times through the evening hours,
with mainly snow expected when precipitation is most intense. The
initial band of heavier precipitation will arrive in the 00Z-04Z
period across most sites, with the band possibly not impacting BRD
in a significant manner. After this initial band light
precipitation will linger through the night. Ceilings will be
generally IFR with visibility MVFR much of the time due to the
wintry mix. Light winds out of the south through the forecast,
generally less than 10 knots but with a few gusts approaching 20
knots in the afternoon.


&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  39  30  39  22 /  20  80  30  20
INL  42  32  38  17 /  20  70  50  30
BRD  40  31  42  22 /  40  40  10  10
HYR  41  31  42  24 /  10  70  30  20
ASX  42  31  43  25 /   0  80  40  30

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...Winter Weather Advisory from 7 PM this evening to 9 AM CDT
     Friday for MNZ011-012-019>021.

LS...None.
&&

$$

UPDATE...GSF
SHORT TERM...Grochocinski
LONG TERM...JJM
AVIATION...JJM



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