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Area Forecast Discussion (AFD)

Issued by Duluth, MN (DLH)

                            
000
FXUS63 KDLH 231729 AAA
AFDDLH

Area Forecast Discussion...UPDATED
National Weather Service Duluth MN
1229 PM CDT Mon Sep 23 2019

.UPDATE...
Issued at 1229 PM CDT Mon Sep 23 2019

Please see the 18Z Aviation discussion below.

&&

.SHORT TERM...(Today through Tuesday)
Issued at 236 AM CDT Mon Sep 23 2019

An upper level low will exit to the east this morning, but with
minor instability in the low levels some shower activity still
remains. This should diminish as the morning progresses. Clouds
should clear and it should be a very pleasant first day of fall
with highs right around 70.

A brief period of high pressure will build Tuesday morning before
a jet streak begins to nose into the area on the back side of
another long wave upper trough. A cold front extending south from
a broad surface low in Canada and 850 flow providing a moisture
tap will set the stage for thunderstorm development. A decent
amount of shear will be present as well given the low level
southerly flow and upper level northwesterly flow, so expect some
storms to get some nice rotating updrafts which will increase the
likelihood of severe weather. The best combination of all of 
these features is generally south of our forecast area, but it is 
possible a few cells may sneak into the southern portions of our 
forecast area Tuesday afternoon/evening.

.LONG TERM...(Tuesday night through Sunday)
Issued at 236 AM CDT Mon Sep 23 2019

There will be a chance for showers, and at times thunderstorms, 
through much of the extended period. The upper flow over the 
Northland will transition from an upper trough or cyclonic flow to
southwest flow aloft next weekend into early next week.

A longwave upper trough will extend from just west of Hudson Bay 
through the central CONUS Tuesday evening with a cold front at the 
surface extending just west of the Northland. MUCAPE values from 
both the GFS and ECMWF are from 1000-2000 J/KG ahead of the front 
with around 40 knots of deep layer shear. Surface dewpoints will 
climb into the the lower sixties over northwest Wisconsin with plume 
of PWAT values around 1.25 inches into northwest Wisconsin. There 
will be a threat for strong to severe storms Tuesday evening over 
northwest Wisconsin into adjacent areas of Minnesota. Wednesday will 
be cooler with highs from the mid fifties to lower sixties. There 
will be a chance for showers through the day, highest over far 
northern Minnesota. Gusty westerly winds will also occur with gusts 
25 to around 30 mph.

Another shortwave and surface low will bring the chance for showers 
back into the region Thursday into Friday morning. Instability is 
weak so we kept the mention of thunder out of the forecast for now.

High pressure will build in Friday night and it will be a cool night 
as 850mb temperatures are forecast to be -1C to 4C by 12Z Saturday. 
If skies are able to clear widespread frost will be possible, 
especially across northern Minnesota. We have some low POPs over 
portions of the Northland Friday night into Saturday, but if the GFS 
and ECMWF solutions remain consistent, we will be able to remove 
them with later updates.

An upper trough will dig along the west coast next weekend causing 
the upper flow over the Northland to become southwest. The upper 
trough will slowly move east into early next week with a low 
pressure system developing and moving into the region and bringing 
widespread rain/storms from late in the weekend into early next 
week. The weekend looks to be quite cool with highs from the lower 
fifties to lower sixties.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1229 PM CDT Mon Sep 23 2019

VFR through the afternoon and into the evening with high pressure
building over the region. Expect fair weather cumulus to continue
developing across the region with ceilings around 3.5-5 kft. This
is already shown over much of the Minnesota Arrowhead and along
northern portions of northwest Wisconsin per visible satellite. 

Winds will remain light and skies relatively clear tonight. Expect
radiation fog to develop at HIB, HYR, BRD and potentially INL.
Visibilities will be in the MVFR range with IFR possible at HYR.
Any radiation fog is expected to lift by 13-15Z as the mixed layer
develop and winds pick up per the RAP/NAM. Showers and potentially
a few thunderstorms move into INL towards the end of the TAF.
Uncertain at this time on how widespread the thunderstorm activity
will be. Expect showers and storms at all other terminals after
18Z. 

&&

.MARINE...
Issued at 236 AM CDT Mon Sep 23 2019

A weak of ridge of high pressure will replace a trough of low 
pressure today...with the ridge passing east of the lake tonight. 
West to northwest winds will back to southwest today for most 
areas and remain below 15 knots. A cold front will then move 
through the region late Tuesday into Tuesday night. Southwest 
winds less than 15 knots will continue Tuesday then they will back
to west Tuesday night and increase late into Wednesday. Winds 
will increase to 15 to 20 knots with higher gusts late Tuesday 
night into Wednesday. Conditions may become hazardous for small 
craft. Thunderstorms will also occur late Tuesday into Tuesday 
evening, some of which could be strong and produce strong wind, 
hail, and frequent lightning. 

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  69  51  72  50 /   0   0  50  70 
INL  69  52  68  47 /   0   0  70  70 
BRD  72  53  74  51 /   0   0  30  40 
HYR  71  49  75  51 /   0   0  30  80 
ASX  71  49  76  51 /   0   0  40  80 

&&

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

$$

UPDATE...WL
SHORT TERM...Wolfe
LONG TERM...Melde
AVIATION...WL
MARINE...Melde