Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 202338
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
638 PM CDT Tue Jun 20 2017

.SHORT TERM...(This evening through Wednesday)
Issued at 351 PM CDT Tue Jun 20 2017

The trough of low pressure aloft which has resided over the
region for the past several days will continue drifting away from
the Northland tonight. Ridging aloft and surface high pressure
will move across Minnesota and into Wisconsin overnight with
clearing skies expected. Winds will diminish as the ridge axis
passes through the area tonight, which will allow for efficient
radiational cooling. Have nudged low temperatures a little cooler
than the bias-corrected consensus blend. With afternoon dewpoints
in the 40s, fog is a possibility. Several of the high-res
deterministic models feature overnight lows in the upper 30s for
inland sections of the Arrowhead and portions of northwest
Wisconsin. With the afternoon dewpoints and weak surface advection
this evening, opted to keep temps in the 40s for all but the
highest elevation areas. The ridge slides east of the Northland on
Wednesday and a warm front will lift northward across the region.
Look for warmer, near normal, temperatures for mid-week with
highs in the low to upper 70s for most locales, and 60s along the
North Shore where a lake breeze will keep temps a little cooler.
Scattered showers are possible as the warm front moves through the
area. A few brief strong thunderstorms are possible. While the
Storm Prediction Center has included much of the CWA in a Marginal
Risk for severe thunderstorms, think the most likely timing will
be with the cool front moving through the Northland Wednesday
night.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 351 PM CDT Tue Jun 20 2017

A persistent upper-level low will bring continued chances of
showers and some thunderstorms over the Northland through the
extended forecast period, along with some cooler than normal
temperatures over the weekend.

A vertically-stacked area of low pressure continues to be progged
by the 20.12Z synoptic guidance, which should be situated over
the Saskatchewan and Manitoba provinces by Wednesday evening. The
upper- level winds look to be strong, with a 130 knot jet streak
overhead on the southern periphery of the upper low. Showers and
thunderstorms should be on the increase as 850-700 mb layer warm
air advection that will be exiting eastward will be quickly
followed up by a surface cold front. The warm air advection ahead
of the cold front will help to build some modest instability ahead
of the cold front boundary, with MUCAPE values generally between
a few hundred up to 1000 J/kg. Storms could become better
organized by some decent deep-layer shear present, with 0-6km
shear values of 55 to 65 kts through Wednesday night. Long mid- to
upper-level hodographs may support convective organization. Also,
there could be some good downpours with these storms as the
GFS/NAM model Pwat values are progged between 1 to 1.5 inches, but
the cold front will quickly scour out the better moisture. Given
the modest instability, but stronger deep-layer shear, the Storm
Prediction Center has expanded a Marginal Risk of severe weather
across a good portion of the Northland, including all of our
western counties, and our southern tier of northwest Wisconsin.
The cold front will pass through the Northland early Thursday
morning, leading to mainly dry conditions during the day Thursday.
Both the GFS and NAM model soundings also indicate Thursday looks
to be pretty gusty, especially over the northwestern half of the
forecast area. Low-level lapse rates look to steepen thanks to
diabatic heating during the day. This should help to deepen the
boundary layer, which will help to mix down stronger winds from
aloft through momentum transport. Areas from the Brainerd Lakes
northeast towards the Iron Range and points northwest could see
wind gusts between 20 to 25 kts possible, with some stronger gusts
possible the further northwest you go.

Another cold front boundary, with an associated mid-level
shortwave will dive southward Friday morning and afternoon, which
could lead to another chance of showers and storms. There is some
uncertainty regarding the amount of moisture available for these
showers and storms on Friday as the GFS and NAM are showing
varying degrees of saturation within the atmospheric column, with
the NAM going drier than the GFS. Compared to the CMC/ECMWF
models, the GFS is still the most bullish with precipitation, and
instability amounts as well compared to the rest of the guidance.
With the majority of the models indicating lower chances of
precipitation, leaned toward lower POPs for Friday. A strong push
of cold air advection associated with a more robust cold front
will move through for Saturday morning, so chances of showers and
should increase. Instability looks weak, at least during the
morning hours, so if thunderstorms did occur, they would most
likely be in the afternoon and evening hours. However, there is
some uncertainty in the amount of instability that will be in
place this far out. A secondary low- amplitude shortwave trough
will then dive southeastward over the region Sunday, maintaining
small chances of POPs. This northwest flow regime will help keep
temperatures below average through the weekend, with highs in the
mid to upper 60s across the Northland from Friday through Sunday.

Surface high pressure looks to build over the southern United
States for Monday and Tuesday, which could help to block the
pattern of these areas of low pressure, causing us to get a few
more shots of precipitation. Temperatures will also be on the
uptick as well, returning to more seasonal values.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 636 PM CDT Tue Jun 20 2017

High pressure will bring VFR conditions throughout the TAF period.
A warm front will begin to push northward across the region on
Wednesday, resulting in a bit thicker cloud cover. A few showers
will also be possible in the afternoon, especially at KINL.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  49  71  54  75 /  20  40  50  10
INL  44  72  52  72 /  20  60  60  10
BRD  50  76  55  76 /  10  40  40  10
HYR  47  76  58  76 /  10  30  40  20
ASX  50  75  56  76 /  20  30  40  10

&&

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

$$

SHORT TERM...Huyck
LONG TERM...JTS
AVIATION...DAP



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