Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 191817 AAB

Area Forecast Discussion...UPDATED
National Weather Service Duluth MN
1217 PM CST Sun Feb 19 2017

Issued at 1217 PM CST Sun Feb 19 2017

Update for new 18Z Aviation Discussion below.


.SHORT TERM...(Today through Monday)
Issued at 314 AM CST Sun Feb 19 2017

Some light fog has developed around the Brainerd Lakes area this
morning, which may expand through the mid-morning hours today as a
surface high pressure ridge continues to slowly move to the east.
The ridge axis should be situated over our far eastern counties
by 12Z this morning, and nearly out of the forecast area by 15Z.
As temperatures increase this morning, any fog that does develop
will diminish. Mid to high clouds will advance into the region
today, but a dry low-level profile as indicated by latest RAP
model soundings should keep conditions dry today.

The big story for the short-term period will be a potent mid- to
upper-level system that will bring chances of precipitation across
the Northland. An upper-level trough will translate northeast
across the Intermountain West and into the region. An
intensifying upper-level jet streak will support upper-level
divergence, along with an associated mid-level trough and surface
cold front. The 19.00Z GFS/NAM models are showing strong
isentropic lift with this system. The thermal profiles are still
suggesting P-TYPES to be all rain, which has been the going trend
for the last several days. One question mark has been the
potential for thunder as instability has been somewhat marginal.
0-1 km MLCAPE values are fairly small, with values approximately
up to 50 J/kg. Investigation of the NAM/GFS soundings are more
favorable for elevated CAPE, with higher values between 100-200
J/kg. The Storm Prediction Center does have an area south of a
Brainerd Lakes to Taconite Harbor line, and all of northwest
Wisconsin within the "general" thunder mention. The best
destabilization appears to be along our southwestern counties, so
will continue mention of isolated thunder mainly along the
southwestern one-third of our forecast area for Monday afternoon.
The GFS is indicating a good push of southerly flow, which will
increase moisture through the column. PWAT values over 1 inch are
progged by the GFS model, so QPF amounts should be pretty
substantial with this system. Through Tuesday morning, total QPF
amounts could range between one-quarter to three-quarters of an
inch across the Northland. The heaviest rainfall amounts appear to
be on Monday afternoon, so the afternoon commute looks to be a
wet and drab one. Moreover, a tightening surface pressure
gradient and intensifying 850 mb level winds will support gusty
southerly winds Monday, with gusts possibly up to 25 knots.

.LONG TERM...(Monday night through Saturday)
Issued at 253 AM CST Sun Feb 19 2017

The cold front exits the forecast area Monday night bringing an
end to the precipitation from west to east. The instability is
lost quickly at 00Z Tuesday and have removed the mention of
thunder. By late Monday night, a mix of rain and snow is possible
along the east end of the BWCAW to Grand Portage as temps cool. A
break from the precipitation comes Tuesday and Tuesday evening as
high pressure drifts overhead. 850mb temps are still warm, from 5
to 8C and max temps will be well above normal with near record
highs possible. Tuesday night through Wednesday night an area of
low pressure will scoot through the region, starting in the
Dakotas, move through southern Minnesota and reach the eastern
Great Lakes by 12Z Thursday. Expecting a mix of rain and snow as
the temps will be borderline for any one PTYPE. The passing of the
low still points to the start of a pattern change and a return to
a winter regime. 850mb temps begin in the single digits Celsius
Tuesday night and drop into the single digits below zero Celsius
late Wednesday night. Model differences begin to show up Thursday
through Saturday with regards to the possibility of a snow event.
The ECMWF is the most bullish taking the system from southeast
Colorado through Green Bay. The GFS is farther southeast with its
low track from southeast Colorado to southern lower Michigan. The
GEM track is to the northwest of the ECMWF and slower. Used a
blended approach to account for these differences, which favors
the GFS. This system will have temps cold enough so that the
majority of the precipitation will fall as snow. Some accumulation
is expected, but the track differences preclude any mention at
this point.


.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1217 PM CST Sun Feb 19 2017

An area of VFR cirrus/stratus will move northeastward across the
terminals this afternoon and early this evening. This band of
clouds marks the location of the upper-level warm front. Radar
echoes over central and northwest Minnesota indicate an impressive
area of virga associated with this band. There could be a few
sprinkles at BRD, HIB, and INL as the band moves through, but feel
dry air in the mid- and low-levels will continue to evaporate the
precipitation before reaching the ground.

A low-level jet will develop tonight ahead of an approaching storm
system and LLWS is expected at all sites. Forecast models continue
the "wet bias" with ample low-level moisture for low stratus or
fog once again tonight. Since very little fog has formed during
the previous several nights, will ignore the overly moist guidance
and hold onto a scattered layer at MVFR altitudes. Rain showers
will move into the terminals from the southwest on Monday morning.
Think winds will become gusty thanks to entrainment and mixing
processes, so introduced wind gusts with the showers and ended the
LLWS potential.

Overall confidence in this forecast is above average.


Issued at 1217 PM CST Sun Feb 19 2017

For record highs and record warmest low temperatures for Duluth
and International Falls, please see the Public Information
Statement (PNSDLH) issued by our office this morning.


DLH  50  36  49  35 /   0  10  90  60
INL  49  37  50  32 /   0  10  90  60
BRD  55  43  55  33 /   0  20  70  20
HYR  54  40  54  37 /   0  10  90  70
ASX  54  36  56  39 /   0   0  90  70




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