Area Forecast Discussion
Issued by NWS Duluth, MN

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000
FXUS63 KDLH 161406
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
906 AM CDT Sat Sep 16 2017

.UPDATE...
Issued at 906 AM CDT Sat Sep 16 2017

Updated to adjust pops to current radar and trends. The
precipitation will move NE or dissipate this morning. As
indicated by previous forecast, there will be a break before the
next round develops later this afternoon with the front coming
through the area.

UPDATE Issued at 737 AM CDT Sat Sep 16 2017

Line of showers and storms moving through eastern Carlton and
eastern Pine counties at 730 am. More showers and isolated storms
moving into northwest Wisconsin from west central Wisconsin.
Updated to account for these trends. Rest of the forecast in the
ballpark.

&&

.SHORT TERM...(Today through Sunday)
Issued at 333 AM CDT Sat Sep 16 2017

An area of low pressure was located over western Minnesota with a
quasi stationary frontal boundary snaking easterly through the
southern portion of the forecast area. A cold front extended
southward to another low center in western Kansas, while an inverted
trof was extending into northwest Minnesota. Meanwhile, a closed mid
level circulation was over the eastern Dakotas/Minnesota border at
08Z. Scattered showers and a few thunderstorms were dotting the
landscape in the strong warm air advection regime located over the
northern third of the region. Some cold air advection was occurring
from 850 to 700mb and this was the leading edge of additional
showers and storms from Aitkin county north to St. Louis county.
1000 to 2000 J/kg of MUCAPE covered the forecast area, but some
MUCIN was keeping the storms in check.

The surface low will meander around the area and reach northwest
Wisconsin by late afternoon. Expect showers and storms to be in the
vicinity of the surface low for much of the day as embedded impulses
in the southwest flow aloft move across the region. PWATS ahead of
the low and its trofs/fronts will be in the 1.5 to 1.75 inch range
through the day. Any storm will have the potential for heavy rain,
with the most likely area being northwest Wisconsin ahead of those
aforementioned features. Strong storms are possible with some small
hail and gusty winds with the heavy rains. The threat of excessive
rainfall is limited as the high PWAT corridor is over northwest
Wisconsin where CREST soil moisture values are generally less than
40 percent. This, combined with the sandy soils, will keep any
flooding potential minimal. The models are in general agreement as
this location has the best chance to see heavy rains.

Tonight, the surface low and its boundaries will be kicked off to
the northeast with the arrival of a strong short wave trof moving
through the Dakotas in the evening and across the region overnight.
Expect the showers and storms to continue for the evening, but start
to show a diminishing trend from west to east through the night as
the best forcing remains in the vicinity of the surface low. High
pressure builds into the area from the west overnight. The upper
trof departs on Sunday with the high pressure drifting nearby.

.LONG TERM...(Sunday night through Friday)
Issued at 333 AM CDT Sat Sep 16 2017

High pressure will briefly build into the region late Sunday night,
however the high will quickly move into the central Great Lakes by
early Monday, while a shortwave ejects into the Northern Plains.
This will bring chances of rain showers on Monday. Flow will become
southerly at the surface and at 850 hPa per the GFS/GEM/ECMWF, which
will advect warmer air into the Northland. Expect warmer readings on
Monday in comparison to Sunday with highs in the low to mid 60s
throughout the region.

High pressure will nudge back into the region late Monday night into
Tuesday. Meanwhile, a trough will dig into the Pacific Northwest,
while a surface low develops across Saskatchewan/Alberta/Montana.
This will tighten the pressure gradient across the the region, which
will bring gusty winds on Tuesday. Winds will become northeasterly
off of Lake Superior in response to the pressure falls off to the
west. Temperatures along the shoreline may be a bit too high
especially if flow is stronger off of the lake.

Shower and thunderstorm chances return late Tuesday night through
Wednesday as the trough over the Pacific Northwest lifts across the
Northern Plains into Ontario. At the surface, a cold front will
slide eastward through the Dakotas into Minnesota and Wisconsin.
Expect strong southerly flow aloft advecting warm moist air into the
region. 0-6 km bulk shear will be increasing along and behind the
front. Ahead of the front there may be few hundred J/kg of MLCAPE to
work with. Will need to continue to closely monitor as strong
thunderstorms will be possible. There are some differences between
the GFS/ECMWF/GEM with timing the trough/front moving through. Right
now the latest GFS is the outlier moving the system through the
quickest, while the ECMWF/GEM are much slower. Behind the front high
pressure will build in. However, the timing of the wave will have
implications on the forecast for Wednesday afternoon. The
faster solution would result in a mostly dry Wednesday afternoon
across the Northland, while the slower solution would keep things
wetter. Have opted to lean towards the slower, wetter ECMWF/GEM
solution at this point.

A cutoff will rotate across Alberta/Saskatchewan, while another
trough digs into the Southwest US. In response to the trough
digging into the Southwest, lee cyclogenesis will occur somewhere
across the Central/High Plains. This will bring shower and
thunderstorm chances Thursday afternoon through Friday. Cannot
pinpoint a specific time at this point as there are significant
differences in timing and intensity of the system developing.

Temperatures will be on the rise through the extended with highs
getting into the 70s by late in the week. Expect lows temperature
readings in the 50s by late in the week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 642 AM CDT Sat Sep 16 2017

The active weather pattern that has impacted the Northland for
the last few days will continue as an area of low pressure and
cold front boundary sweeps through today. MVFR to VLIFR conditions
were observed this morning across the Northland TAF terminals.
VLIFR cigs/vsbys continue over KDLH, but is expected to improve as
on-shore flow off Lake Superior weakens later this morning.
However, IFR/LIFR conditions are expected to continue at KDLH.
There will be a brief respite from showers and thunderstorms later
this morning and early afternoon before ramping up again in the
late afternoon and evening hours, per the HRRR and NAM model
guidance, as the cold front advances eastward. Winds are expected
to shift to more westerly behind the front. Confidence is a bit
lower on the timing of showers/storms for KBRD, so used VCSH/VCTS.

On-shore flow will increase once again later this evening, which
should bring lower cigs/vsbys to KDLH.


&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  70  50  60  45 /  70  90   0   0
INL  61  45  56  40 /  50  60  10   0
BRD  66  48  61  46 /  50  50   0  10
HYR  80  54  63  43 /  60  70  10   0
ASX  80  55  64  43 /  60  70  10   0

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...Beach Hazards Statement until 8 PM CDT this evening for WIZ001.

MN...Beach Hazards Statement until 8 PM CDT this evening for MNZ037.

LS...Small Craft Advisory until 10 AM CDT this morning for LSZ121-
     140>148.

&&

$$

UPDATE...Stewart
SHORT TERM...GSF
LONG TERM...WL
AVIATION...JTS



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