Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 252024
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
324 PM CDT Sat Mar 25 2017

.SHORT TERM...(This evening through Sunday)
Issued at 314 PM CDT Sat Mar 25 2017

Cloud cover is expected to increase again overnight tonight ahead of
a stacked area of low pressure that will be situated over the mid
Mississippi River Valley overnight. A lobe of PVA will eject from
this low pressure system, along with increasing 850-700 mb layer
warm air and moisture advection, will support increasing chances
of precipitation over northwest Wisconsin this evening, and then
from the Brainerd Lakes northeast towards the Minnesota Arrowhead
Sunday morning. East to northeast on-shore winds off of Lake
Superior will continue through the day Sunday, which should advect
some cooler temperatures over land. This may lead to the
development of some patchy fog along the North Shore. Confidence
is not high that any dense fog will develop despite what a few of
the models were progging, including the RAP and HRRR models, and
to a lesser extent - the WRF ARW/NMM models. Cloud cover and
stronger winds due to the favorable fetch should help limit the
fog, but dew point depressions still look favorable. Due to the
cooler temperatures being advected on-shore, still think some
patchy fog is likely, but don`t think it will be dense. Therefore,
introduced patchy fog over the North Shore overnight.

The main concern for the overnight hours will be the precipitation
types overnight. As the PVA and warm air advection arrives, the
thermal profiles are expected to cool. Deepening moisture profiles,
as indicated in the RAP/NAM model soundings, along with cooling sfc
temperatures, will lead to mainly freezing rain across portions of
northwest Wisconsin, with the possibility of snow/sleet mixing in.
The most uncertainty for this forecast comes from the exact
temperature profile as the sfc temperatures will be right at
freezing. Any change in the sfc temperatures, either plus or minus
a degree, will have big changes in p-types. The guidance is
hinting at favorable sfc temperatures for freezing rain along the
higher elevations of the Gogebic Range in Iron county. Due to the
potential for a wintry mix, with freezing rain being the primary
p-type expected, decided to issue a Winter Weather Advisory for
Iron county tonight and into mid Sunday morning until temperatures
warm up. Smaller changes of freezing rain are possible along the
North Shore overnight as well, but the heaviest QPF is expected
over northwest Wisconsin, so not expecting as much ice
accumulation along the North Shore. Ice accumulation in Iron
county could be up to a tenth of an inch, with the greatest
amounts expected in the higher elevations of the Gogebic Range.

Precipitation will transition to all rain late Sunday morning
through the afternoon as the temperatures increase. Temperatures
will remain near or above seasonal averages during the day Sunday,
with decreasing chances of precipitation Sunday afternoon and
evening.

.LONG TERM...(Sunday night through Saturday)
Issued at 314 PM CDT Sat Mar 25 2017

No major storms appear in the offing for the upcoming week, but
there will be periodic chances for light precipitation, both at the
beginning of the period, and again later in the week.

At the beginning of the extended periods Sunday night and Monday,
ongoing light precipitation will be winding down and ending as the
slow-moving upper low over the middle Great Lakes region slowly
pulls away to the east.

As the eastern North American trof axis amplifies a bit early to mid
week, high pressure will strengthen slightly over Canada, and should
be sufficiently strong to push a weak surge of slightly colder air
southward into the western Lakes region Tues-Wed.  This should also
be sufficient to minimize precip chances during this time with
general large-scale subsidence.

Beyond Wednesday, the medium range models have significant
differences in both amplitude and timing of various weak
disturbances that will affect the Northland through the remainder of
the 7 day forecast window, which is also supported by the rather
large spread in the ensemble solution space.  The region should
transition to a slightly warmer airmass with time, but there will
also likely be periodic chances for light precip during the Thursday-
Saturday time range, and it seems likely that there will be at least
a couple of short time windows where light wintry mixed precip will
be possible across the region.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1255 PM CDT Sat Mar 25 2017

MVFR/IFR ceilings are hanging on longer than previously thought
due to the additional development of boundary layer stratocumulus
and persistent on shore easterly flow. Ceilings should have a
tendency to rise some between now and 00-03z this evening, but
thereafter, we expect MVFR/IFR conditions to redevelop at most
sites. As an upper level low moves northeastward into Wisconsin
Sunday morning, precipitation - mainly in the form of rain - will
slowly spread north/northwest-ward with the greatest potential of
affecting KDLH/KHYR. We have backed off precip chances in
KHIB/KBRD from the previous issuance. The forecast of KHYR is
especially problematic and low confidence. We expect it to rain,
but whether or not it will be freezing rain hinges on a degree or
two of surface temps late tonight/Sunday morning. For this
issuance, we believe only a short period of <= 32F surface temps
will minimize the potential for any freezing rain and ice
accumulations.


&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  30  38  30  46 /  40  40  10  10
INL  29  47  28  48 /   0   0   0  10
BRD  32  45  32  54 /  20  20  10  10
HYR  33  42  31  48 /  60  50  30  10
ASX  32  39  30  45 /  60  50  30  10

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory from 11 PM this evening to 9 AM CDT
     Sunday for WIZ004.

MN...None.
LS...Small Craft Advisory until 4 AM CDT Sunday for LSZ121-140>148.

&&

$$

SHORT TERM...JTS
LONG TERM...Miller
AVIATION...Miller



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