Area Forecast Discussion
Issued by NWS Duluth, MN

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777
FXUS63 KDLH 170545
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1245 AM CDT Thu Aug 17 2017

.UPDATE...
Issued at 1245 AM CDT Thu Aug 17 2017

Updated aviation section below for 06Z TAF issuance.

UPDATE Issued at 910 PM CDT Wed Aug 16 2017

Adjusted pops to account for the current radar trends. Still
expecting a slight chance of thunder later tonight. Not
anticipating any flooding as soil moisture is fairly dry yet
according to the CREST and SAC-SMA soil moisture. Made some other
minor tweaks.

&&

.SHORT TERM...(This evening through Thursday)
Issued at 310 PM CDT Wed Aug 16 2017

The focus remains on the widespread moderate to heavy rainfall
forecast across the Northland through Thursday in association with
an area low pressure lifting through the Upper Midwest. The latest
trend in the models has been to shift the axis of heaviest rain a
bit farther east, resulting less rainfall forecast across
northwest Wisconsin and more across parts of northeast Minnesota.
The RAP seems to have a good handle on the situation, especially
in its earlier depiction of a dry slot moving for the middle of
today. Used extra weighting towards the RAP on timing and
rainfall through tonight.

A deepening area of low pressure over northwest Iowa, as of during
the middle of this afternoon, is expected to lift across southern
Minnesota through tonight and into central/northern Wisconsin
Thursday. It will become somewhat vertically stacked tonight as it
deepens. This low will bring a period of deep moisture and
moderate large-scale forcing for ascent across the Northland.
Precipitable water values will increase to 1.5 to 1.75 inches. The
forcing will producing widespread moderate to heavy rain across
the Northland, primarily tonight through early Thursday afternoon,
as the low lifts across the region. The heaviest rains, about
1.5" to perhaps as much as 2.5", are now expected to fall in a
wide band from central Minnesota through northeast Minnesota in
association with the deformation zone on the northern and western
periphery of this system.

There could be some thunder here and there through Thursday,
mainly across the southern forecast area due to the potential for
elevated- based instability and forcing from embedded shortwaves
or from the main upper-level low. The instability will likely be
fairly weak, so the storms should only result in occasional
lighting, heavier rainfall rates, and breezy winds.

The rain will gradually pull out of the Northland Thursday
afternoon, with drier air filtering into the western forecast area
as the low departs. Considering the rain and high moisture, even
once the deeper cloud cover exits the western forecast area in the
afternoon, broken/overcast cumulus cloud cover should quickly
develop, meaning not much sunshine until maybe close to sunset.
Expect a cooler and humid day, with highs from the low 60s in the
Arrowhead to the middle and upper 60s elsewhere.

.LONG TERM...(Thursday night through Wednesday)
Issued at 310 PM CDT Wed Aug 16 2017

An upper ridge will be over the Pacific northwest into
Alberta/British Columbia Thursday night with a trough from Hudson
Bay through the central CONUS. The flow will become zonal over the
region through the weekend into early next week then another
trough will move over the region early next week.

The strong low pressure system will be moving away from the
Northland Thursday night with lingering showers ending overnight
for most areas. Additional rainfall will be light Thursday night.
Brief weak ridging will develop overnight behind the departing low
but another shortwave in northwest flow will be moving in during
the day Friday. There will be a chance for showers and a few
thunderstorms roughly from near Walker to Siren and points west
and south during the afternoon and evening.

Dry conditions will occur Saturday as the low level flow becomes
south to southwest. Highs will range from the upper seventies to
lower eighties. Another shortwave and front will move through the
Northland Saturday night into Sunday bringing another chance for
showers/storms to parts of the area. Highs Sunday will again be in
the upper seventies to lower eighties.

A stronger shortwave will bring a better chance for
showers/storms to the region later Sunday night into Monday night.
A dry period is then expected Tuesday into Wednesday. High
temperatures Monday through Wednesday will be in the seventies.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1245 AM CDT Thu Aug 17 2017

Rainfall overnight and into Thursday morning will keep MVFR/IFR
CIGS in place across all terminals. DLH and HYR may dip to LIFR
CIGS for a time later tonight and Thursday morning with bands of
heavier rainfall. Uncertainty still exists with regards to the
threat of TS at HYR, so have kept VCTS in place through daybreak
Thursday to account for this. Rainfall will end from west to east
through the day Thursday and into Thursday evening, however, CIGS
will be slow to improve and a return to VFR conditions may hold
off until the early morning hours on Friday. Not anticipating any
issues with low VSBYS through the period with winds remaining in
the 5-10kt range through much of the period.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  58  63  55  75 /  90  90  20  10
INL  58  64  51  77 / 100 100  10  10
BRD  60  69  55  77 / 100 100   0  30
HYR  63  68  55  74 /  90  60  40  10
ASX  61  70  57  76 /  70  60  50  10

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...Small Craft Advisory until 4 PM CDT this afternoon for
     LSZ140>147.

&&

$$

UPDATE...BJH/GSF
SHORT TERM...Grochocinski
LONG TERM...Melde
AVIATION...BJH



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