Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 170522
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1222 AM CDT Wed May 17 2017

.UPDATE...
Issued at 739 PM CDT Tue May 16 2017

The fog around the higher terrain of the Twin Ports area has
improved quite a bit, so we dropped the dense fog advisory early.
Fog will likely redevelop later tonight.

UPDATE Issued at 712 PM CDT Tue May 16 2017

The forecast was updated through this tonight to speed up how
quickly this evening`s round of showers and storms move through
and out of the forecast area, as well as delay and refine the
precipitation chances for the second round of showers and storms
expected to lift into northwest Wisconsin late tonight. There
remains a threat of severe storms, including the potential for
tornadoes, across northwest Wisconsin this evening. The greatest
threat is the far southeast forecast area, especially southern
Price County.

&&

.SHORT TERM...(Tonight)
Issued at 315 PM CDT Tue May 16 2017

Thunderstorms and heavy rainfall are expected tonight, with the
main focus over northwest Wisconsin and adjacent areas of east-
central and northeast Minnesota. Thunderstorms will redevelop in
central Minnesota and lift northeastward into the Northland
through this evening. The potential for training storms remains in
play which could result in one or more swaths of very heavy
rainfall this evening. With the rainfall from yesterday moving
through the area creeks and rivers, decided to issue a Flash Flood
Watch, in coordination with our neighbors. WPC has included
northwest Wisconsin and part of Pine County in the Slight Risk
area of the Day 1 excessive rainfall forecast. Strong northward
moisture transport will keep precipitable water values up to 1.5
inches through this evening. Rain amounts tonight will be highest
along the I-35 corridor and over northwest Wisconsin. One-half
inch to 1.5 inches of rain is expected, but higher amounts are
likely where the strongest storms track.

In addition to the flooding potential tonight, there remains a
slight risk of severe thunderstorms over much of northwest
Wisconsin. NAM BUFR soundings from HYR feature effective shear of
around 35 kts with 0-6 km shear around 45 knots along 3-3.5 kJ/kg
of MUCAPE are favorable for large hail and damaging wind gusts.
Low- level shear seems to preclude much of a tornado threat at
this time, however, the potential cannot entirely be ruled out.

.LONG TERM...(Wednesday through Tuesday)
Issued at 315 PM CDT Tue May 16 2017

The Northland has a rather wet and cool forecast through the
weekend, but warmer weather might return early next week. There
are multiple rounds of rain forecast through the weekend, with
temperatures about 10 to 15 degrees cooler than seasonal normal
temperatures.

A subtle front will stall from northeast Ontario to southern
Minnesota early Wednesday, including across northwest Wisconsin.
Meanwhile, a potent shortwave will lift north into the Northland
late tonight and early Wednesday. This wave will bring a surge of
moisture and widespread synoptic lift, setting off showers and
thunderstorms, mainly focused along and near the stalled front.
Precipitable water values could reach 1.5 inches. Parts of
northwest Wisconsin could get moderate to heavy rainfall. About
0.25" to nearly 1" of rainfall is forecast across northwest
Wisconsin, but there could be locally higher amounts.

There will likely be areas of fog Wednesday morning, but
increasing north-northeast flow will likely lift it by late
morning. Temperatures will be cool across the north and near Lake
Superior, but more seasonably warm across well-inland areas of
northwest Wisconsin.

A potent, vertically stacked area of low pressure will lift from
the Central Plains Wednesday to the Minnesota and Wisconsin areas
Wednesday night. This low will bring another surge of moisture of
moisture and even more potent and widespread synoptic lift across
the Northland. Much of the Northland can expect moderate to heavy
rainfall from late Wednesday through Thursday morning, with the
heaviest amounts again in northwest Wisconsin. Fortunately, most
of this rain will be less convective in nature, and more
stratiform in nature. The best chances of thunder are in Price
County in the far southeast forecast area. The stratiform nature
will limit the flooding the threat, but certainly areas of
northwest Wisconsin that get quite a bit of rain over the next
couple days could have flooding in low-lying areas. Widespread
rainfall of 1.25" to 1.5" is forecast in northwest Wisconsin,
about 0.25" or more from the Arrowhead to central Minnesota
Minnesota, but no rain for north- central Minnesota.

High pressure will build into south-central Canada and the
US/Canada border area Thursday afternoon into Friday, providing
the Northland a period of dry and sunnier weather. The GFS,
European, and Canadian models are indicating another potent area
of low pressure will likely bring widespread moderate to heavy
rain across the Northland late this week and/or over the weekend.
The GFS and European are in fairly good agreement on the timing,
with the rain affecting the Northland late Friday night and
through Saturday night, but the Canadian brings the rain late
Saturday night through early Monday. If the GFS/ECMWF solution
pans out, then more seasonal weather might return for Monday, but
the slower Canadian would suggest cooler and cloudier weather for
Monday. The threat of thunder with this round of rain looks fairly
low at this point, but the GFS suggests a threat of thunder
across the southern forecast area when it lifts the warm front
close or into the southern forecast area Saturday evening.
Otherwise, instability should be fairly low due to the cooler
conditions, at the surface and aloft, across the Northland.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1222 AM CDT Wed May 17 2017

A large area of showers and thunderstorms is expected to once
again overtake the Northland weather overnight and into the
remainder of the TAF period. The exception will be in the KINL
area which should generally see dry weather. Otherwise, we will
see myriad conditions, with IFR/LIFR conditions with fog at KDLH
to MVFR to IFR conditions elsewhere. The best chance of showers
and thunderstorms will be confined to an area from KDLH to KBRD
and southward into KHYR. Very heavy rainfall is possible
throughout the period.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  49  56  39  50 /  30  70  90  40
INL  46  57  38  55 /  40  10  10   0
BRD  53  61  44  57 /  20  70  80  30
HYR  56  62  42  51 /  80  90  90  50
ASX  48  55  39  47 /  60  90  90  60

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...Flash Flood Watch through Thursday afternoon for WIZ003-004-008-
     009.

MN...None.
LS...Gale Warning from 10 PM this evening to 4 PM CDT Thursday for
     LSZ121-146>148.

     Small Craft Advisory from 10 PM this evening to 4 PM CDT
     Thursday for LSZ140>145.

&&

$$

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



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