Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 180549 AAC

Area Forecast Discussion...UPDATED
National Weather Service Duluth MN
1249 AM CDT Sun Jun 18 2017

Issued at 1249 AM CDT Sun Jun 18 2017

An updated aviation discussion is below for the 06z TAF issuance.


UPDATE Issued at 956 PM CDT Sat Jun 17 2017

CAPE values have been diminishing this evening and the stronger
thunderstorms that occurred earlier have ended. Mostly showers
were occurring across the Northland with some embedded thunder as
of late evening. This will continue overnight and coverage of the
showers and thunderstorms will be greatest across northern


.SHORT TERM...(This evening through Sunday)
Issued at 325 PM CDT Sat Jun 17 2017

A closed upper low over northwest Ontario this afternoon will loosen
its grip on the forecast area by Sunday as the main low center moves
to southeast Ontario. Will see embedded pieces of energy in the fast
flow aloft rotate over the region this afternoon through Sunday.
These features will lead to showers and storms this afternoon
through tonight. The storms will diminish somewhat after sunset with
loss of daytime heating, except in northwest Wisconsin where
enough CAPE lingers to support convection into the late night.
Showers, however, will persist through the night and into Sunday.
Isolated thunderstorms are expected to form in the late afternoon
over the Arrowhead, near the Twin Ports, and much of northwest
Wisconsin. The storms will fire in the axis of MUCAPE of up to
1000 J/kg Sunday.

The upper flow becomes northwesterly on Sunday with cold air
advection ensuing. Some gusty winds are possible by the afternoon in
response to the arriving colder air. Max temps will be cooler as
well with plenty of clouds and showers around. Min temps
tonight will be in the 50s. Highs on Sunday will be in the 60s.

.LONG TERM...(Sunday night through Saturday)
Issued at 325 PM CDT Sat Jun 17 2017

Sunday evening with the surface low now well west of the forecast
area, we are in a regime of northwest cyclonic flow with cold air
advection going on.  Due to the resulting steep low level lapse
rates, we should get another round of diurnally driven showers and
thunderstorms during the afternoon that gradually diminish during
the evening and overnight hours.  Monday will be similar, though
with a little less convective activity due to the moderating cold
air aloft and warmer surface temperatures.  Monday night a shortwave
dives through the flow and should help keep showers going overnight,
though. Tuesday should be quieter, with a little drier air and
subsidence behind the Monday night wave to keep diurnal
convection reduced. Temperatures will be near to below normal
Monday but warm to near normal for Tuesday.
A stronger shortwave is expected to move through the area Wednesday
and Wednesday night.  Models have been struggling with this feature,
and the GFS remains stronger than the ECMWF, but on recent days the
ECMWF did not even have this wave at all. Have kept to the chance
pops for now, but confidence in it is increasing a little at this
time.  Confidence diminishes for anything beyond that though, as the
models are depicting an even stronger wave forecast to move through
on Friday, but there is little agreement beside the presence of a
strong shortwave in the upper level flow in this time range, but not
in strength, timing or track.  For now we are carrying some slight
to chance pops for pretty much Thursday through Saturday, but we are
going to have to wait until we are closer in before we can find some
drier periods in there.   Temperatures through this period should be
near normal, though would not be surprised to see an above normal
day or two depending on the track of the shortwaves.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1249 AM CDT Sun Jun 18 2017

An upper level trough will remain over the region into Sunday night
with several shortwaves rotating through it. Showers and some
embedded thunder will continue tonight and be most numerous over the
southeast half of Northland including much of northwest Wisconsin.
The showers will diminish for a time late tonight into Sunday
morning but more will then develop as colder air aloft continues to
move in along with shortwave energy. Mostly VFR conditions were
occurring late this evening but MVFR ceilings are expected to
develop overnight into Sunday morning then gradually lift Sunday
afternoon/evening. Northwest winds will increase on Sunday and be
gusty at times.


DLH  53  66  49  67 /  70  50  20  20
INL  52  62  47  65 /  20  50  20  20
BRD  55  65  50  70 /  80  30  10  20
HYR  56  67  51  69 /  90  60  30  30
ASX  53  67  51  68 /  80  70  40  30




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