Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 201136
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
636 AM CDT Thu Jun 20 2019

.UPDATE...
Issued at 636 AM CDT Thu Jun 20 2019

Updated for the 12Z aviation discussion.

&&

.SHORT TERM...(Today through Friday)
Issued at 405 AM CDT Thu Jun 20 2019

The focus in the short term will be how widespread will the
showers be and how far east to bring them. Weak surface high
pressure was over or just north of Lake Superior this morning and
it isn`t forecast to move much today into Friday. An upper level
trough will move southeast today into Friday reaching the North
Plains on Friday. Downstream from this trough will be an elongated area
of low pressure. A shortwave ahead of the main trough will affect
the Northland today into tonight. However, overall forcing isn`t
very strong today into tonight and the main area of low level
moisture transport remains mostly west and south of the Northland.
The trend in much of the models has been to slow the eastward
progress of the showers today and we made those adjustments and
have a chance for showers and a few thunderstorms in the Walker
and Brainerd Lakes area today with a few showers possible over far
northern Minnesota as well. We limited POPs tonight to portions of
our west and south following model consensus. We expect highs
today in the seventies, except it will be cooler around Lake
Superior with off lake winds a bit stronger than yesterday.

Warm air advection increases on Friday and PWAT values will be on
the increase, especially over the southwest half of the Northland
where values will increase to 1 to 1.4 inches. We again slowed
chances for showers/storms down and kept areas dry east of a line
from International Falls to Two Harbors to Mercer. We increase
POPs west of that line as moisture transport increases through the
day. A few strong storms may develop over the Brainerd Lakes
region late in the day into the evening as MUCAPE increases to
500-1000J/KG in the afternoon. Highs will be in the lower to
middle seventies, but off lake winds will again keep lakeside
areas quite a bit cooler.

.LONG TERM...(Friday night through Wednesday)
Issued at 405 AM CDT Thu Jun 20 2019

A large upper low over eastern Montana will gradually deepen and
move up into southern Saskatchewan Friday night, continuing north
through Saturday.  This should bring a plume of deep moisture, warm
air advection and isentropic lift across the area in bands Friday
night through Saturday night, with this area of lift not shifting
east of the area until at least Sunday, depending on the model.  We
are currently in a risk for excessive rainfall, and while the slow
moving pattern and potential for repeated thunderstorms over the
same areas is concerning, the Precipitable Water values are not
especially out of the ordinary through the weekend.  We are also in
a marginal risk for severe weather on Friday evening, but much is
going to depend on developing enough instability during the day. By
Saturday the risk for severe storms is diminished, but the heavy
rainfall threat remains.  Soils have been getting dry lately, so we
may only get some localized flooding from repeat storms or higher
rates in urban areas.  The cloud cover and precipitation along with
east to southeast winds should produce near to cooler than normal
temperatures and have kept highs mainly in the mid 60s to mid 70s
Saturday, with lows in the mid 40s to mid 50s. Sunday the models
diverge enough to produce uncertainty in when the precipitation will
end, with the ECMWF and Canadian more similar in timing, pulling it
out of the CWA Sunday afternoon, while the GFS is slower and keeps
precipitation chances going.  These differences are mainly due to
the different handling of a shortwave that moves through the main
upper trough, and depending on how well that feature is phased with
the main trough, and the shortwave`s speed and track are all
variables that are quite different.  For now have maintained chance
pops through Sunday, but have allowed temperatures to rise a
category over Saturday, in hopes of a period of sunshine.

Early next week the phasing differences between the main upper
trough and the faster moving shortwaves within it continue to
produce differences in the models for the area, making it difficult
to pick out a consistent dry period in the Monday through Tuesday
time frame, and have maintained some chance pops throughout.  Warmer
air should begin nosing into the area from the southwest as the main
upper trough shifts farther east, and have allowed highs to creep
into the 70s to around 80.  Wednesday the models seem to agree that
we should get a ridge to build over the area, bringing warmer
temperatures at at least a short period of drier weather. This does
not last long though, and precipitation chances return for Thursday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 636 AM CDT Thu Jun 20 2019

VFR conditions expected through this TAF period. Showers, and
possibly also thunderstorms should approach KBRD between 21z and
05z, and have included VCSH groups until a better idea of timing
can be resolved. East to southeast winds will become gusty in the
17z-00z time range as a low pressure system moves toward the
area.

&&

.MARINE...
Issued at 405 AM CDT Thu Jun 20 2019

An approaching low pressure system will cause winds increase out of
the northeast and gradually increase through the day today, then
diminishing slightly overnight  before increasing again on Friday,
and doing the same on Saturday.  Winds are not currently expected to
get strong enough to produce waves of over 3 feet today, but
conditions may approach or exceed Small Craft Advisory on Friday and
Saturday.  Friday the main concern is for the tip of the lake, but
expands to a broader portion of western Lake Superior on Saturday.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  71  47  67  48 /  10  10  30  40
INL  77  48  76  54 /  20  10  10  40
BRD  74  54  73  56 /  40  40  50  70
HYR  77  51  73  53 /  10  10  30  40
ASX  68  44  71  49 /  10  10  20  30

&&

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

$$

UPDATE...LE
SHORT TERM...Melde
LONG TERM...LE
AVIATION...LE
MARINE...LE



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