Area Forecast Discussion
Issued by NWS Duluth, MN

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195
FXUS63 KDLH 241741
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1241 PM CDT Sun Sep 24 2017

.UPDATE...
Issued at 1241 PM CDT Sun Sep 24 2017

Updated for the new 18Z Aviation Discussion below.



UPDATE Issued at 954 AM CDT Sun Sep 24 2017

A line of showers has developed from Burnett county south toward
the Twin Cities. This is in an area of theta-e advection and some
upper level divergence. Showers are also developing along the
western edge of the forecast area from Cass County northeast to
near International Falls. Stubborn fog along the head of Lake
Superior from near Foxboro to Superior and east along the shore.
Expect the fog to burn off shortly. Adjusted pops and weather to
account for these observations.

&&

.SHORT TERM...(Today through Monday)
Issued at 340 AM CDT Sun Sep 24 2017

The most recent wave of precipitation is moving slowly north on the
nose of a low level jet that is impinging upon a boundary at 850mb.
Decent warm air advection and frontogenesis along the boundary is
serving to focus showers and thunderstorms from the northern
Minnesota border west-southwest towards the Fargo area before
extending south into central Nebraska.  Temperatures remain very
warm for this time of year, and several sites approached record high
temperatures yesterday.  Today will be quite similar to yesterday,
though additional cloud cover over yesterday should keep us from
getting quite as warm and have gone with forecast highs a few
degrees shy of records for this time of year.  The warm temperatures
shift into the western CWA as the surface boundary also shifts west
today. The 850mb boundary and resulting frontogenesis will lift
north of the forecast area.  This will keep showers and
thunderstorms focused west of the forecast area, and am carrying
lower pops only across the western areas.  Tonight and Monday the
surface front finally makes good progress to the east and the higher
pops should shift slowly across the forecast area tonight and
Monday.  Temperatures to also be cooler Monday due to the increased
cloud cover and rainfall.

.LONG TERM...(Monday night through Saturday)
Issued at 348 AM CDT Sun Sep 24 2017

After a flashback to summer this weekend, we return to our regularly
scheduled fall weather next week to end the month of September.
Highs in the 50s to near 60 and lows in the 40s. Light rain across
the region on Tuesday, then a low chance for scattered light rain
showers Thursday. Partly to mostly cloudy most days, clearing out
late in the week with a possible frost/freeze Friday night as a
broad area of high pressure builds in across the Midwest.

On the synoptic scale a pattern change early to mid week as the deep
trough-ridge pattern over the CONUS breaks down. The deep mid-level
trough over the western states lifts northeast across the northern
Plains towards Ontario Tuesday into Wednesday with a broad mid/upper
level ridge then building over the western states. As this ridge
builds to the west, a broad longwave trough develops over the Great
Lakes region leading to a typical northwest flow pattern over the
Upper Midwest. This pattern will allow for cooler Canadian air to
advect southward into the Upper Great Lakes region mid to late week.
A broad surface high pressure develops over the Canadian Prairie in
response to the building mid/upper level longwave ridge to the west,
with this area of high pressure building southeastward towards the
Great Plains and Midwest towards the weekend. Northerly flow at low
levels is likely to bring some of the coolest air of the season
across the Upper Midwest by the weekend.

Monday night through Tuesday evening...the quasi-stationary frontal
boundary across the region over the past few days finally exits,
located over northwest Wisconsin by Monday night. The mid-level
shortwave trough lifts northeast across the region Tuesday creating
broad-scale lift which will help produce light stratiform rain
across much of the Northland behind the front. Rain ends towards
Wednesday morning. Highs in the low/mid 50s behind the frontal
boundary in northern Minnesota, warmer in the 60s in northwest
Wisconsin. Lows in the 40s Tuesday night.

Wednesday...Partially clearing skies expected to develop in the west-
northwest flow behind the front. Highs in the mid 50s to low 60s
with drier air making it feel much less humid - dew points in the
mid 40s.

Thursday...As a broad longwave ridge develops over the western
states into the Canadian Rockies, a mid-level shortwave trough will
approach from the north Thursday leading to a chance for light rain
showers across the Upper Great Lakes region. Cooler air streams in
from the north associated with this disturbance with 850mb temps
falling below zero Celsius across much of the Northland. Highs in
the mid 50s to low 60s, lows Thursday night in the upper 30s to near
40.

Friday and beyond...High pressure builds in with broad subsidence
leading to a clearing trend. Highs in the 50s Friday, likely the
coolest highs of the season so far for many locations. Friday night
could see some locations falling to near the freezing mark depending
on cloud cover.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1241 PM CDT Sun Sep 24 2017

Northeast MN and northwest WI had widespread VFR conditions with
warm, southerly flow. A cold front stretching from far northwest
Ontario, through northwest Minnesota, and into eastern South
Dakota, will advance east through the Northland later this
afternoon and through tonight and Monday. It will bring some
showers and thunderstorms this afternoon and evening, mainly
across parts of northeast Minnesota, including KBRD and KHIB. Some
of the storms could be strong.

There will be lowering ceilings and visibility in the wake of the
cold front overnight. Cool and humid northwest flow will bring
LIFR/IFR stratus, but more likely MVFR in parts of northwest
Wisconsin. There will also be a period of significant low-level
wind shear at KHYR late this evening through the wee hours of the
morning, until the strong low-level jet shifts east of KHYR.
Anticipate slow improvement in the ceilings Monday morning.

&&

.CLIMATE...
Issued at 348 AM CDT Sun Sep 24 2017

I have included todays record high temperatures for easy
reference. The current forecast shows that it is possible to break
a record again at Ashland, and Duluth, Brainerd and Hibbing are
within 6 degrees.

Record Highs for September 24...

Duluth................85 in 1892
International Falls...82 in 1917
Brainerd..............85 in 1935
Hibbing...............82 in 2007
Ashland...............87 in 1935

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  79  59  62  51 /  10  60  60  70
INL  71  49  55  46 /  70  80  20  40
BRD  80  55  58  50 /  60  60  50  60
HYR  85  63  72  55 /   0  50  60  60
ASX  87  62  70  53 /   0  40  60  70

&&

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

$$

UPDATE...Grochocinski
SHORT TERM...LE
LONG TERM...JJM
AVIATION...Grochocinski
CLIMATE...LE



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