Area Forecast Discussion
Issued by NWS Duluth, MN

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000
FXUS63 KDLH 190917
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
417 AM CDT Sat May 19 2018

.SHORT TERM...(Today through Sunday)
Issued at 417 AM CDT Sat May 19 2018

Several areas of rain showers with occasional rumbles of thunder
stretched from south-southwest to north-northeast over the
Northland this morning. A cool front extended from southern
Minnesota northward into northeast Minnesota with a weak surface
low centered over the southwest arm of Lake Superior. Isentropic
lift over the boundary and mid-level divergence supported the
existing showers and the development of additional showers over
central and portions of northern Minnesota. The easternmost area
of showers was over the Arrowhead, with a break over western Lake
Superior, and another area of showers over Burnett and Washburn
Counties. The strongest forcing for ascent was found over the
Arrowhead and shower coverage and intensity there should continue
to increase through 7 AM. Several additional broken lines of
showers and embedded storms have developed and strengthened over
north-central Minnesota southwest into Cass, Crow Wing, and Aitkin
Counties. Convection in that area was supported by divergence
above 725 mb ahead of a shortwave which stretched from northwest
Ontario into northeast South Dakota. GOES-16 water vapor imagery
supported the RAP analysis.

The front will slowly progress east-southeastward today moving
across northwest Wisconsin through the late afternoon. As the low-
level jet weakens later this morning, think the shower and storm
coverage will wane for a time, but will increase once again by
late morning or early afternoon. Daytime heating should be
sufficient to generate 250 to 750 J/kg of MUCAPE, as indicated by
the RAP and NAM, ahead of the front over north-central Wisconsin.
As the front moves into that environment, shower and storm
coverage should increase. The cool front will slide east of the
Northland by late afternoon/early evening bringing an end to the
precipitation chances. The other concern for today is
temperatures. With high pressure moving into the region behind the
front and winds veering north to northeasterly by late afternoon,
the lake breeze is forecast to move inland. The most drastic
affects will be felt between the North Shore Highlands and the
lakeshore, and southwest of the Twin Ports as far south as the
Pattison Ridge, and inland to near Moose Lake. Timing the
intrusion of the lake airmass will play a significant role in max
temperature readings. Have leaned toward the high-res guidance
solutions, which holds the lake breeze at bay until mid/late
afternoon. Clouds over the Arrowhead into the I-35 corridor will
inhibit temperatures as well. Look for high temps to reach the
low 50s northeast to the middle 60s northwest and low 70s over
interior northwest Wisconsin.

High pressure will gradually move through the region tonight and
Sunday keeping skies mainly clear. A very dry airmass overhead
tonight should allow temperatures to bottom out in the low to
upper 30s. Efficient mixing on Sunday will push afternoon humidity
into the 20 to 25 percent range for most of the area. There is
some uncertainty regarding the lake breeze for Sunday. With the
center of the ridge near the Northland, and a weak surface wind
field over the area, the lake breeze may hug the lakeshore for
much of the day. Have followed that concept and kept the affects
on temperatures limited to areas within a few miles of Lake
Superior.

.LONG TERM...(Sunday night through Friday)
Issued at 417 AM CDT Sat May 19 2018

Sunday night through at least Tuesday the area will be in between
systems, with the current wave departing off to the east, with
another shortwave moving across Iowa and Illinois, with a ridge of
high pressure at the surface over the area. This will keep our
weather generally dry and quiet. Have increased our diurnal range
on both Max and Min T, anticipating that the dry conditions are
going to produce warmer highs and cooler overnight lows than
consensus forecast can capture.

Beginning Wednesday an upper low begins to push into the longwave
ridge over the central CONUS, which the models are not handling
in a very consistent manner, so have poor confidence in the
forecast beginning around Thursday, with some of the models
bringing the upper low in stronger, larger and slower than others,
producing some fairly large differences in the sensible weather
for the forecast area. For now we have a consensus forecast of
slight chance to chance POPs advancing into the area beginning on
Thursday and continuing into Friday and Saturday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1219 AM CDT Sat May 19 2018

An area of low pressure and cold front was over Minnesota late this
evening and will continue to move east, exiting the Northland late
Saturday morning or early afternoon. Showers will occur just ahead
and we behind the front tonight with coverage expected to decrease
on Saturday. A few thunderstorms will also be possible along the
front as it moves through eastern Minnesota and far western
Wisconsin. MVFR/IFR conditions will expand from west to east tonight
into Saturday then decrease late Saturday morning into the afternoon.

A period of low level wind shear will occur at KDLH through about
09Z.


&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  57  35  64  40 /  20   0   0   0
INL  61  33  71  36 /  20   0   0   0
BRD  65  39  70  41 /  20   0   0   0
HYR  68  36  69  37 /  20   0   0   0
ASX  60  32  61  36 /  40   0   0   0

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...None.
&&

$$

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



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