Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 240845
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
345 AM CDT TUE MAY 24 2016

.SHORT TERM...(Today through Wednesday)
Issued at 345 AM CDT Tue May 24 2016

The main challenge for today is chances for additional showers and
storms through this evening. Forecast confidence is low due to
poor model agreement and lack of definitive features for forcing.
Used a wide blend for pcpn chances and capped at 30%.

The Northland finds itself today in a warm and humid airmass in
the wake of a passing shortwave trough exiting to the east, and
lifting shortwaves through the Northern Plains in the sw flow
aloft. There is very light low level flow, but a 50 to 70 knot
jet stream aloft.

Early this morning...There will be some lingering showers and
storms across the eastern forecast area as a shortwave trough
finishes exiting the Northland. Additional showers and storms are
possible over the west central forecast area due to the pva caused
by shortwaves lifting through the Northern Plains. Fog is possible
across much of the Northland because of the moist boundary layer
and lack of wind.

Today...There will likely be building instability across the
Northland with daytime heating. Passing shortwaves could help
spark off isolated/scattered showers and thunderstorms by this
afternoon. Complicating the forecast is the wide variety of model
guidance, ranging from developing storm complexes swinging through
the Northland this afternoon (ARW/NMM/NCEPWRF) to very little pcpn
(GFS20). The lack of low level flow makes it difficult to believe
the the former solutions because of the lack of flow to feed those
supposed storms. Whereas the GFS20 seems too dry considering the
warm and relatively humid airmass today and passing shortwaves,
which could easily develop scattered convection. Also, it appears
surface high pressure may settle over Lake Superior this
afternoon. Cooler easterly flow from Lake Superior may work itself
inland and cause low level convergence (and a means for storm
development) as it buts up against westerly and southern flow.
Decided to use a wide blend of the models, leaning a little bit
more towards the drier GFS, but providing low pcpn chances for at
least most of the forecast area. High temperatures should range
from the lower 70s near Lake Superior to the upper 70s and low 80s
inland.

If any storms develop today, they may tap into an environment of
500 to 1250 J/kg of mixed layer cape, 30 to 40 knots of deep layer
(0 to 6 km) wind shear, and freezing levels around 10 kft agl.
Despite the lack of low level flow, any storms will be able to tap
into decent westerly steering flow, allowing any storms to move
and graze on instability, instead of remaining stationary and
quickly dissipating. Given the environment, there could be
isolated strong storms capable of producing hail and gusty winds.
The SPC thunderstorm threat outlook would likely be more than
marginal if it were not for the lack of low level wind to feed the
storms, as well as the overall lower confidence in today`s
forecast.

Tonight...Any showers and storms should dissipate with the waning
instability after sunset and as an upper level ridge lifts into
the Northland, suppressing convection. Some models are producing
light pcpn near Lake Superior overnight, but this would more
likely be drizzle because of the likelihood of fog and low stratus
developing from the cool and humid easterly flow from the Lake.
Lows should range from the upper 40s near Lake Superior to the low
to middle 50s well inland.

Wednesday...The upper level ridge will lift north of the
Northland, while a wnw to ese orientated shortwave trough will
likely lift into the Northland. The lifting trough will bring a
wave of moisture and increasing chances of showers and storms. The
chances of thunder will be better across the western and southern
forecast area because of the cool easterly flow from Lake Superior
limiting heating near the Lake. Any thunder over the Lake will
likely be the result of elevated convection caused by the pva from
the shortwave. Prefer the GFS20 and SREF instability, which
depicts much less instability near Lake Superior, unlike the more
robust NAM12. High temperatures will likely range from the upper
50s near Lake Superior to the upper 60s and lower 70s inland.

.LONG TERM...(Wednesday night through Monday)
Issued at 345 AM CDT Tue May 24 2016

An unstable southwest flow will lift several waves across the
region through the upcoming week...keeping ongoing
rain/thunderstorm chances in the forecast through much of the
extended period.

A closed low will makes its way into the upper plains wednesday
night...tracking across the northern minnesota boarder thursday.
The low will lifting a large swath of showers and thunderstorms
over MInnesota and wisconsin during this time. locations in
portions of central may see and earlier end to the convection
thursday morning...depending on the placement of the dry slot.

Northeast winds will prevail Friday and Saturday as the next wave
lifts into the northern plains...keeping conditions cooler near
Lake Superior. Models are in good agreement that the next low
tracks northward across minnesota during the Holiday
weekend...bringing increasing PWATs...along with widespread
showers and thunderstorms.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 345 AM CDT Tue May 24 2016

A weak frontal boundary draped across the region this evening has
served as the focus for showers and thunderstorms to move across
the terminals. This is shifting slowly east, and expect the
precipitation to slowly come to an end by 09z. Behind the
convection where precipitation fell, expect fog to develop during
the early morning hours. For now have gone with a prevailing MVFR
visibility, but some IFR visibilities are possible and have
included a tempo group for that at the most likely sites. After
18z Tuesday expect additional showers and thunderstorms to develop
in the vicinity of the terminals, but do not have confidence
enough to put either prevailing or tempo groups for any of the
terminals. Northeast winds are expected to develop over Lake
Superior after 21z due to an approaching low, producing MVFR
ceilings for KDLH by 06z...with IFR conditions possible later.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  74  49  60  50 /  30  10  50  60
INL  79  52  74  53 /  30  20  50  60
BRD  82  56  73  56 /  20  10  60  50
HYR  80  52  73  57 /  30  20  60  60
ASX  74  46  63  51 /  50  10  50  60

&&

.DLH Watches/Warnings/Advisories...
WI...None.
MN...None.
LS...None.
&&

$$

SHORT TERM...Grochocinski
LONG TERM...Graning
AVIATION...Graning/LE



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