Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 182043

Area Forecast Discussion
National Weather Service Duluth MN
343 PM CDT Sun Jun 18 2017

.SHORT TERM...(This evening through Monday)
Issued at 343 PM CDT Sun Jun 18 2017

Closed upper low will loiter over the Northland tonight and
Monday keeping below normal temperatures and a chance of showers
and thunderstorms in the picture.

A persistent and slow moving upper low is forecast to gradually
slide eastward during the next 36 hours. Showers and thunderstorms
are expected to gradually weaken and dissipate tonight with the
loss of daytime heating and the arrival of very weak subsidence.
Several small areas of vorticity have been observed on GOES-16
imagery today with a more prominent, but weaker, vort max over
north-central Minnesota. Shower intensity has increased this
afternoon ahead of the broader vort max where partial sunshine has
generated several hundred Joules of MUCAPE. Within the last hour
a few of the updrafts have been strong enough to support thunder.
Think the coverage and intensity is near a diurnal maximum and a
downward trend should begin before 00Z. Patchy fog is possible
over most of the Northland tonight as winds diminish. Another
round of showers and storms is expected Monday. A shortwave trough
will rotate around the west side of the upper low, but is
expected to remain northwest of our CWA by 00Z Tuesday. However,
shower and thunderstorm coverage will increase during the after
ahead of the approaching disturbance. Temperatures will remain
below normal tonight and Monday with lows in the upper 40s to
middle 50s expected. Highs on Monday will top out around 60
degrees in the Boundary Waters and near 70 degrees near Pine City.

.LONG TERM...(Monday night through Sunday)
Issued at 343 PM CDT Sun Jun 18 2017

Monday night we get one last surge out of this upper low we have
been under since yesterday. Expect another round of showers and
thunderstorms as a shortwave dives through the area overnight.
Dynamics and instability parameters support getting some
thunderstorms with this shortwave, though severe storms are
unlikely for the forecast area. Quieter weather settles in for
Tuesday with a ridge axis shifting to just west of the forecast
area at the surface, with northwest flow continuing to keep
temperatures near to slightly below normal.

Wednesday a shortwave we have been watching for a few days moves
towards and across the area. It is likely to generate an MCS
Tuesday night in the vicinity of the Montana/North
Dakota/Saskatchewan/Manitoba border region, which should then
slide east-southeast along the baroclinic zone to affect at least
part of the area on Wednesday. Models have been vacillating on
timing and track of this system, so confidence is increasing on
pops for Wednesday.

After Wednesday confidence drops off sharply as models differ in
phasing and timing of waves in the broad upper level troughing
that sets up over the northern CONUS beginning Wednesday and
Thursday. For now it seems prudent to keep to the slight/chance
pops in the consensus forecast for Thursday through next Sunday,
with near to slightly below normal temperatures.


.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 127 PM CDT Sun Jun 18 2017

Low pressure system over eastern Lake Superior will result in
north/northwest flow across the region this TAF cycle, but with a
moist boundary layer, combined with cool temperatures aloft has
produced scattered showers and MVFR to VFR conditions. There may
be a few storms, but confidence on any storms affecting specific
TAF sites at this time is low and have left out of terminals for
now. Gusty conditions have also developed at a few locations.
Additional improvement is expected this evening with most
locations returning to VFR, but then deteriorate again after 09Z
to MVFR. Improvement back to VFR and an increase in winds should
begin after 12Z, though not all sites to improve that much until
after 18Z.

DLH  52  66  48  70 /  50  20  20  10
INL  49  62  46  69 /  20  20  20  10
BRD  52  69  50  71 /  20  40  40   0
HYR  52  68  49  70 /  30  20  30  10
ASX  53  67  50  69 /  50  20  20  10




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