Area Forecast Discussion
Issued by NWS Duluth, MN

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000
FXUS63 KDLH 161726
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1226 PM CDT Sun Jul 16 2017

.UPDATE...
Issued at 1226 PM CDT Sun Jul 16 2017

Please see the 18Z Aviation discussion below.

&&

.SHORT TERM...(Today through Monday)
Issued at 414 AM CDT Sun Jul 16 2017

Cooler today as an area of high pressure over Lake Superior results
winds off the lake and mainly sunny skies. Clear skies overnight
with some patchy fog possible, then warmer Monday as a warm front
builds in from the west. Thunderstorms may develop along and ahead
of this warm front, some of which could be strong to severe, but it
appears the better chance for storms will be Monday night when the
cold front behind this warm front sweeps across northern Minnesota.

Today the stratus/fog which developed overnight should gradually
burn off as high pressure builds over Lake Superior. East to
northeast winds across western Lake Superior will result in cooler
temperatures along the lake shore, with highs struggling to reach
the mid 60s along the shoreline, in the 70s farther inland. East
winds around 10-15 mph near Lake Superior, not as strong inland.

Tonight clear skies across the Northland, which may lead to
radiation fog development as temperatures fall to the 40s in much of
northeast Minnesota and parts of northwest Wisconsin. Some mid to
high level clouds may move in across north-central Minnesota in the
night. Conditions appear favorable for the aurora (AKA northern
lights) per the NOAA/NWS Space Weather Prediction Center, and those
interested in viewing it should have good weather conditions. Fog is
most favorable along the north shore, but otherwise skies should be
clear in northeast Minnesota and northwest Wisconsin for much of the
darkest hours. At Duluth Astronomical Twilight ends at 11:32pm and
begins at 3:00am, so between those hours is when the sky will be
darkest.

Monday mid to high level clouds will increase across north-central
to northeast Minnesota. Southerly winds will advect a much warmer
and moist airmass in from the south, with some highs near 90 not out
of the question for north-central Minnesota including Brainerd and
Walker; elsewhere in the low 80s, except along the north shore where
highs may be as cool as the mid 60s (eg. up in Grand Marais). A
strong cap will exist through the day, and while some guidance does
depict thunderstorms developing within the warm sector, the
likelihood of scattered to widespread convection breaking out during
the day appears low; see the long term portion of this discussion
for details on the severe weather threat tonight. Breezy southerly
winds in the warm sector Monday, with gusts up to 25 mph expected.

.LONG TERM...(Monday night through Saturday)
Issued at 414 AM CDT Sun Jul 16 2017

The Northland can expect a week of seasonably warm weather with
periodic opportunities for showers and thunderstorms. The focus is
on late Monday afternoon and Monday night, which may bring a period
of strong to severe thunderstorms. There may be another stormy
period late in the week, some time late Friday or Friday night.

As of Monday evening, there will be a mid-level ridge axis
stretching from far northeast Ontario to the Central Plains. A
shortwave trough will stretching from far northern Ontario to the
eastern Dakotas, and a cold front will stretching from far northwest
Ontario to northwest Minnesota, and through southeast North Dakota
to central South Dakota. The Northland will have warm and humid
southerly flow, with the cold front likely nearing the corner of the
northwest forecast area. Dew point temperatures will be in the upper
60s to near 70 degrees across the western forecast area.

There will be modest large-scale forcing associated with the
approaching shortwave trough to help trigger thunderstorms along and
ahead of the cold front late Monday. These storms would be
developing in a very warm and humid airmass, an environment likely
to feature 1500-3000 J/kg of MUCAPE, 30-40 knots of 0-6 km deep
layer wind shear, and 1.5-2.0 inches of precipitable water. These
environment will support organized convection, possibly discreet
supercells during the onset in the evening when the storms are
entering the northwest and western forecast area. The abundant
moisture will also help these storms produce heavy rain. The
strongest storms will be capable of large hail, strong winds, and
heavy downpours of rain. The storms will spread east through the
Northland overnight with the advancing cold front and passing
shortwave trough.

The cold front movement will slow down or stall Tuesday, and there
could be redevelopment of showers and storms across the southern
forecast area Tuesday into Tuesday night. High pressure will build
into the Northland from the northwest Tuesday into Tuesday night,
providing a short period of drier weather as the front finally
shifts south of the Northland. However, another shortwave trough
will pass through the Northland Wednesday, which might bring another
round of showers and thunderstorms to the Northland.

The high pressure will then likely provide a period of clearer and
drier weather Thursday through much of Friday. Confidence in the
forecast drops Friday onwards. The European model suggest a subtle
mid-level ridge will move into the Northland by Saturday. However,
the GFS has a potent wave swinging through the Northland late Friday
through early Saturday, bringing a period of strong large-scale
forcing for ascent for thunderstorms across all of the Northland.
Therefore, the weather could just be warm, or warm and stormy.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1226 PM CDT Sun Jul 16 2017

High pressure will build into the central Great Lakes late
tonight, while a cold front slides into northwest Minnesota. This
will result in VFR conditions through the TAF period. With clear
skies and light winds, there is a low possibility of fog at
KHYR/KBRD/KHIB. Late tonight, the pressure gradient will increase
across north central Minnesota due to the incoming cold front and
exiting high. This will bring low level wind shear to KINL and
there is potential for a brief window of LLWS at KBRD based on the
NAM/RAP/GFS guidance.

After 14Z expect low level wind shear to subside as the boundary
layer develops and the mixed layer grows. This will bring gusty
winds to KINL/KBRD mid Monday morning. In addition, there is
potential for showers and thunderstorms at KINL. Have held off on
the mention of thunder at this point, but there will be increasing
chances of storms as Monday progresses.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  67  48  77  64 /   0   0  10  60
INL  78  51  83  59 /   0  30  50  60
BRD  78  57  86  67 /   0  10  30  60
HYR  73  52  80  67 /   0   0  10  40
ASX  66  49  80  64 /   0   0  10  60

&&

.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...WL
SHORT TERM...JJM
LONG TERM...Grochocinski
AVIATION...WL



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