Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 252025

Area Forecast Discussion
National Weather Service Duluth MN
325 PM CDT Thu May 25 2017

.SHORT TERM...(This evening through Friday)
Issued at 325 PM CDT Thu May 25 2017

Surface ridge axis covered much of the forecast area at 20Z. A
lake breeze had worked inland along the north and south shores of
Lake Superior and has eroded much of the cloud cover from earlier.
Elsewhere, plenty of cumulus clouds were found. Some higher clouds
were moving into from the west. Expect the clouds to fill back in
and to become more widespread through the night ahead of the well
advertised system for the weekend. Some showers are expected with
the first wave of energy in the Red River Valley at 20Z. These
showers will be isolated in nature initially as it has to overcome
the dry air that is in place due to the departing high.

The next round of showers arrives on Friday with some isolated
thunderstorms possible in the afternoon. This activity will
be associated with a bit stronger vorticity maxima that will eject
from the closed upper low in Manitoba. There are model differences
with the timing of this round of showers and storms, as well as the
coverage and the amount of QPF. Used a blended approach for Friday
to account for these differences.

.LONG TERM...(Friday night through Thursday)
Issued at 325 PM CDT Thu May 25 2017

The main focus of the extended is an upper level cutoff that will
slowly rotate from central Manitoba Friday evening into central
Ontario by late Sunday night. The cutoff then will slide eastward to
the Ontario/Quebec border by mid week. Multiple shortwaves will
rotate around the cutoff and eject into the Northland. This will
bring scattered rain showers through much of the holiday weekend,
but it does not look like any days will be a washout. Friday
evening, Sunday afternoon/evening and Monday afternoon have the best
chance of thunderstorms as there will be a few hundred to 1500 J/kg
of MUCAPE combined with strong forcing. A cold front will slide
through Friday evening providing the forcing necessary for
thunderstorm development, while Sunday and Monday will mainly be due
to surface troughs swinging through from the surface low located
over Ontario. Cannot completely rule out thunderstorms on Saturday
as there is still some instability to work with, but the surface low
will be located well the north of the region. Think that the forcing
is too weak for thunderstorm development, so opted to keep out a
thunder mention on Saturday. Conditions will remain dry for much of
Saturday with shower chances increasing late in the
afternoon/evening as a shortwave digs in from the Eastern Dakotas.
Expect the mildest readings on Saturday with temperatures generally
in the 60s and 70s due to 8 to 10 degree Celsius 850 hPa air
advecting into the region.

Cooler readings are expected for the rest of the holiday as flow
turns northwest at 850 hPa advecting colder air into the region. 850
hPa temperatures range from 0 degrees Celsius to 5 degrees Celsius.
Highs on Sunday range from the upper 50s to upper 60s, while
Memorial Day and Tuesday highs will be the 50s and low 60s. Low
temperatures through the extended period will be in the 40s.

Mid to late next week a ridge axis will build into the Northern
Plains from the Pacific Northwest. At this point there are still
timing and strength differences between guidance with the incoming
high and exiting system. Flow aloft will become more westerly, which
will bring warmer temperatures for Wednesday and Thursday with highs
in the 60s and low 70s.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1236 PM CDT Thu May 25 2017

A 500 hPa ridge will slide from eastern Minnesota this afternoon
into eastern Wisconsin late tonight. Despite the ridge, fair
weather cumulus has developed across the Upper Midwest due
heating with ceilings ranging from 2.9 to 4 kft. Expect the CU
field to remain in place until this evening with gusty winds at
BRD/INL/HIB due to the tightening pressure gradient from the
departing high and cold front. The gusty winds will subside this
evening once the mixed layer decouples per the RAP/NAM.

The front will slide eastward across Minnesota tonight and early
on Friday. This will provide enough lift for rain showers to
develop and in addition, lowering ceilings as the lower levels
moisten. Expect MVFR ceilings to gradually develop and per the
the NAM/RAP/DLHWRF soundings think that IFR ceilings are a
possibility with visibility reduction as fog develops.
Thunderstorms are a possibility at INL/BRD/HIB towards the end of
the TAF period as there is sufficient instability developing
ahead of the front. However, think the possibility is too low at
this point to include in the latest TAF set.


DLH  46  63  48  69 /  30  50  30  10
INL  52  70  46  69 /  40  50  20  20
BRD  54  74  49  73 /  20  30  10  10
HYR  52  70  50  73 /  20  50  30  10
ASX  44  67  49  71 /  30  50  30  10




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