Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 270013
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
713 PM CDT Wed Jul 26 2017

.SHORT TERM...(This evening through Thursday)
Issued at 413 PM CDT Wed Jul 26 2017

Morning sunshine and mild temperatures have popped a bouquet of
cumulus across the Northland this afternoon. A few showers have
been noted in northwest Ontario under the most robust updrafts.
Expect convection to diminish over the next few hours with mostly
clear skies overnight.

Attention then shifts to Thursday. A compact and relatively
vigorous shortwave trough is forecast to dive southeastward
across the Northland. Cloud cover should increase during the
morning, aided with diurnal warming. The boundary layer is
forecast to mix up to around 800 mb by late morning and early
afternoon. With the strong shortwave coming in, think we may see
some robust updrafts and have expanded the POPs with this
forecast. A few updrafts may be strong enough for a few lightning
strikes and have thunder mentioned, as well. Raw GFS soundings
along the North Shore seem to be contaminated by some odd surface
dewpoints yielding >2000 J/kg of MUCAPE and MLCAPE. Modifying
those soundings with more realistic dewpoints brought those
instability values back to earth in the 500-750 J/kg range. A
wedge of warm, dry air aloft may keep deep convection capped, but
expect showers at least.

.LONG TERM...(Thursday night through Wednesday)
Issued at 413 PM CDT Wed Jul 26 2017

Summary: The Northland can expect seasonably warm weather late
this week through the middle of next week. There are some
opportunities for showers and storms, mainly late Saturday through
Sunday, followed by a better opportunity Tuesday and Tuesday
night.

An area of surface high pressure will be over the western Great
Lakes through the first half of the weekend, providing a period of
clear weather through at least Saturday morning. Southwest return
flow will develop Saturday when the high pressure shifts far
enough south of the region. A weak shortwave trough, and trailing
surface reflection, will likely pass through the Northland late
Saturday through Sunday. This wave might be able to generate some
showers and weak storms, but the forcing looks fairly weak at this
time. Kept precipitation chances low at this time.

Surface high pressure will likely keep the Northland dry Monday,
although the Canadian stalls the surface trough across near the
southern forecast area Sunday night and Monday. It shows some
showers and storms across the southern forecast area Monday
afternoon, while the GFS and European keep the region dry because
of either the trough moving well enough south of the Northland or
the trough dissipating.

The GFS, Canadian, and European have a cold front approaching or
moving into the Northland sometime closer to the middle of next
week. The GFS and Canadian are faster in timing compared to the
European and justify chances of showers and storms Tuesday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 713 PM CDT Wed Jul 26 2017

High pressure will bring clear to scattered clouds to the
northland throughout the remainder of the night. There may be some
patchy fog in some spots overnight, but we think it will be quite
spotty and have not included it in the TAF at this point. The most
likely locations would be KHIB and KHYR. A rather potent shortwave
will dive southward across western Lake Superior on Thursday. This
will bring scattered showers and thunderstorms to the region on
Thursday afternoon. Have included VCSH for now, but will need to
continue to evaluate thunder threat in subsequent TAF issuances.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  58  78  55  78 /   0  40  20   0
INL  55  80  54  81 /   0  30  10   0
BRD  59  81  57  80 /   0  10  10   0
HYR  58  80  53  80 /   0  30  20   0
ASX  58  78  53  78 /   0  30  20   0

&&

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

$$

SHORT TERM...Huyck
LONG TERM...Grochocinski
AVIATION...DAP



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