Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 231743

Area Forecast Discussion
National Weather Service Duluth MN
1243 PM CDT Wed May 23 2018

Issued at 1236 PM CDT Wed May 23 2018

Please see latest Aviation Discussion

UPDATE Issued at 1201 PM CDT Wed May 23 2018

There is not much change to the overall forecast philosophy or
theme of message late this morning. The surface ridge axis
continues to very slowly move off to the east, with winds now
gradually becoming south/southeast in most areas. Strong
land/water differential heating today should eventually result in
a decent lake breeze front, but it will likely take until this
evening before the marine layer deepens sufficiently to push
inland by a large distance. We have held on to low chances for
showers/T-storms in the southwest sections of the Duluth CWA late
this afternoon, but by far, the best chances for rain will be
tonight/Thursday morning with the strong warm/moist advection
push driven by the nocturnal low level jet.

We have only made a few very minor changes to the going forecast,
including nudging temps up a degree or two in some areas, and also
some subtle tweaks to wind speed/direction and humidity to fine
tune things for the fire weather user community.


.SHORT TERM...(Today through Thursday)
Issued at 308 AM CDT Wed May 23 2018

The short term will see moisture continue to increase across the
Northland with lower to mid 60s dewpoints becoming widespread by
Thursday afternoon. Upper level ridging today shift east tonight
into Thursday.

Much of the Northland will remain dry today due to the upper level
ridge over the area. However, weak warm air and moisture
advection and increasing instability may be enough for a few
afternoon showers/storms from about the Siren area west northwest
to Aitkin, the Brainerd Lakes and Walker areas. Highs today will
be from around 80 to as high as 85. Off lake winds are expected
to develop through the day cooling lakeside areas.

Moisture advection will increase further tonight with a chance for
showers and thunderstorms over much of the Northland. Severe
storms are not expected, but a few strong storms producing brief
heavy rain and small hail will be possible.

Shower and storm chances will continue into Thursday, but they are
not expected to be widespread and chances will be highest over
western portions of the Northland. A shortwave will be approaching
from the Northern Plains but its affects will be most pronounced
Thursday night. A few strong storms will be possible, mainly late
Thursday afternoon into the overnight. Highs Thursday will be in
the lower to middle eighties and with dewpoints in the lower to
middle sixties, it will feel muggy. Lakeside areas will again be

.LONG TERM...(Thursday night through Tuesday)
Issued at 308 AM CDT Wed May 23 2018

The main areas of focus for the extended forecast period continues
to be a more active weather pattern, with chances of showers and
thunderstorms Thursday night and Friday, with some very warm
temperatures through early next week.

Thursday night and Friday look to have the highest chances of
thunderstorms, with some possibly strong to severe, as a mid-level
shortwave trough advances over southern Canada, with an associated
surface low pressure translating across southern Manitoba and
southwest Ontario Canada. Ahead of the low will be plenty of
instability due to warm and moist air entrenched over the region,
with surface dew points in the lower to middle 60s early Friday
morning, and mixed-layer CAPE values generally in the 500 to 1500
J/kg range. A 30 to 40 kt low-level jet should provide good moisture
advection, with Pwat values around 1.5", which is near 99% of
climatology  per the NAEFS Pwat climatological analysis. 0-6 km bulk
shear of 20 to 30 kts should be a limiting factor for storm
intensity, but with instability as high as it`s progged to be, some
strong or severe thunderstorms aren`t out of the question,
particularly over north-central Minnesota, where a Slight risk of
severe storms are laid out by the Storm Prediction Center. Damaging
winds and large hail will be the main threats.

The mid-level shortwave will slowly dive southeastward over the
region, which will bring a weak cold front through the region
Saturday. Instability shouldn`t be quite as high Saturday as it
should be Friday due to lower surface dew points in the middle to
upper 50s. Still, mixed-layer CAPE values of 500 to 1000 J/kg will
be in place due to the very warm air, with highs expected to be in
the lower to middle 80s. The synoptic scale models are in a bit of
disagreement on the placement of precipitation, but generally looks
to be across our northern counties, closer to the surface low.

From Sunday and beyond, the models tend to be in more disagreement
regarding precipitation chances, but generally, conditions look to
be a bit drier. Forcing looks to be pretty weak as mid-level ridging
develops. There could be a few weak impulses moving over the
Northland through Tuesday, but the GFS/ECMWF/GEM aren`t in good
agreement regarding the areal coverage of precipitation. However,
the models are in better agreement on warm temperatures remaining
over the region. Expected high temperatures from Sunday through
Tuesday remaining in the lower to middle 80s across the area.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1236 PM CDT Wed May 23 2018

Some diurnal cumulus has developed across the region as a weak
warm front will lift northward over the region this evening, with
showers and thunderstorms possible through the overnight. Several
model solutions are showing llws impacting KBRD during the morning
hours around 10Z so further discussions will address this as it
gets closer.


DLH  80  54  81  61 /  10  40  30  50
INL  83  58  86  61 /   0  50  40  60
BRD  83  61  87  63 /  30  30  40  50
HYR  82  60  87  65 /  10  40  20  50
ASX  81  51  86  60 /   0  30  30  50




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