Area Forecast Discussion
Issued by NWS Duluth, MN

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000
FXUS63 KDLH 141815 AAC
AFDDLH

Area Forecast Discussion...UPDATED
National Weather Service Duluth MN
115 PM CDT Mon Aug 14 2017

.UPDATE...
Issued at 115 PM CDT Mon Aug 14 2017

Update for new 18Z Aviation Discussion below.

UPDATE Issued at 1206 PM CDT Mon Aug 14 2017

Showers continued from the Arrowhead into the Iron Range and into
northwest Wisconsin as an upper trough moves through the area. A
few more showers were developing elsewhere as well and we
expanded POPS this afternoon into early evening and added more
thunder.

UPDATE Issued at 642 AM CDT Mon Aug 14 2017

Updated aviation section below for 12Z TAF TAF issuance.

&&

.SHORT TERM...(Today through Tuesday)
Issued at 347 AM CDT Mon Aug 14 2017

An upper level short wave with a closed mid level circulation,
will cross Minnesota this morning, and then into northwest
Wisconsin this afternoon as the mid level circulation opens into a
trof. Several embedded impulses will accompany this system and
have increased pops across much of the area as a result. Even
though there is some instability suggested by the models, cloud
cover may affect the overall potential for thunder. Regardless, do
have a mention of thunder over portions of northwest Wisconsin
this afternoon. The greatest potential for thunder will be over
northern St. Louis east through northern Lake and Cook counties
which each of the models agree upon. Thermodynamic profiles do not
support any mention of hail, nor excessive rain.

Monday evening finds the short wave moving through the eastern
portion of the Wisconsin forecast area before departing. No change
was made to the prior forecast in the early evening as a result.
Brought the pops down for the rest of the evening. No thunder is
expected as instability is diurnally driven. Elsewhere, upper
level and surface ridging are arriving from the west with a
clearing sky. As the high settles overhead late tonight, expect
fog to develop and affect much of the region and linger until
14Z/9am Tuesday.

A dry day is expected Tuesday as the ridging remains over the
area. The models are trying to flatten the upper ridge in the
afternoon with an approaching short wave trof. However, moisture
is lacking and thus a rain free day.

.LONG TERM...(Tuesday night through Sunday)
Issued at 347 AM CDT Mon Aug 14 2017

Tuesday night-Wednesday night a potent upper level shortwave and
associated surface low moves across the upper midwest, bringing a
period of showers and a few thunderstorms to the forecast area.
Models are fairly consistent in depicting that this feature will
affect our area, but the strength and track of the low vary a lot
between models and over the last few runs. That said though, have
raised pops between 09Z Wednesday through 12Z Thursday over the
consensus to depict this greater confidence in this event
happening. The GFS looks overamplified aloft and too strong and
too far north with the surface low, so am favoring a more
moderated solution between the ECMWF and NAM solutions. Since I am
favoring a more southerly solution to the surface low, have
reduced the thunder somewhat. Thursday the precipitation chances
slowly ramp down as the system moves off to the east.

Beyond Thursday there are some pretty large differences in the
synoptics of the forecast. By Thursday evening the general pattern
of low pressure system just to our east and ridging over the west
coast/Rockies is fairly consistent. However, the GFS has a potent
secondary shortwave moving out of the Rockies that is much weaker
in the ECMWF. Over the following 24-36 hours the GFS ramps this
feature up into a fairly strong system that moves a surface low
across the mid Mississippi River valley that just does not exist
on the ECMWF. This makes a pretty big difference in the models by
Saturday, producing large uncertainties in the forecast beginning
on Friday and continuing through the weekend and early next week.
Have stuck with the consensus forecast for now, and will have to
wait and see on how these features resolve in the next few days.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 115 PM CDT Mon Aug 14 2017

Clouds will linger over the Northland this afternoon into the
evening. Expect MVFR ceilings to linger at DLH and HYR for several
more hours before lifting to VFR. Rain showers are expected to
increase in coverage this afternoon as filtered sunshine leads to
marginal instability. Think the showers will diminish early this
evening. Clearing skies and light winds should permit efficient
radiational cooling overnight. Lowered visibilities at DLH, BRD,
HIB, and HYR since the trend for fog development has continued.
Visibility will improve quickly Tuesday morning as fog mixes out
with VFR conditions expected for the remainder of the TAF period.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  67  53  74  57 /  70  10   0  30
INL  76  52  79  57 /  10  10   0  30
BRD  70  53  75  60 /  30   0  10  70
HYR  67  51  77  58 /  90  10   0  30
ASX  69  53  75  56 /  90  10   0  20

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...Beach Hazards Statement until 8 PM CDT this evening for WIZ001.

MN...Beach Hazards Statement until 8 PM CDT this evening for MNZ037.

LS...None.
&&

$$

UPDATE...Huyck/Melde
SHORT TERM...GSF
LONG TERM...LE
AVIATION...Huyck


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