Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 210553 AAB
AFDDLH

Area Forecast Discussion...UPDATED
National Weather Service Duluth MN
1253 AM CDT Fri Jul 21 2017

.UPDATE...
Issued at 1253 AM CDT Fri Jul 21 2017

Update for 06Z Aviation Discussion below.

&&

.SHORT TERM...(This evening through Friday)
Issued at 400 PM CDT Thu Jul 20 2017

A mid level ridge will build eastward from the Upper Midwest
tonight into the central Great Lakes by Friday evening. Behind it,
a warm front will lift northeastward from the central Dakotas into
central Minnesota. Despite the ridge, there is an area of
frontogenesis from 900 hPa to 800 hPa moving into northern
Minnesota late tonight that was associated with the shower/storm
activity over northeast North Dakota/northwest Minnesota earlier
today. The RAP/HRRR guidance has captured this activity best, so
leaned on this guidance for this evenings POPs. Cloud cover will
increase late tonight from west to east due to the incoming warm
front. With relatively clear skies for most of the night and light
winds, expect patchy fog to develop across northwest Wisconsin
and eastern portions of northeast Minnesota. Low temperatures
range from the low 50s in far northeast Minnesota, to the low 60s
in the Brainerd Lakes Region.

The warm front will lift northeastward into the eastern Dakotas
and western portions of Minnesota on Friday. This will bring
increasing chances of showers and thunderstorms especially from
the Brainerd Lakes Region east to northwest Wisconsin. Across the
rest of northeast Minnesota, less certain on shower/storm chances
as guidance has been all over the place. Should have a better idea
on these chances later this evening as the higher resolution
guidance suggests that the forcing aloft originates from the
thunderstorm activity over northwest North Dakota. Regardless,
environmental parameters show 40-50 kts of 0-6 km bulk shear with
a few hundred to 1000 J/kg of MLCAPE. PWAT values are around 1.5
to 2.0 inches from central Minnesota to northwest Wisconsin, which
is around the 90th percentile based on SPC sounding climatology
for MPX. With this in mind, strong to severe thunderstorms are
possible with the threats of large hail, damaging wind gusts, and
heavy rainfall as highlighted in SPCs latest Day 2 Outlook. Expect
another hot and humid day with highs in the upper 70s and low 80s.

.LONG TERM...(Friday night through Thursday)
Issued at 400 PM CDT Thu Jul 20 2017

Friday night we have a continuation of convection potential along
the mid level baroclinic zone draped from northwest Minnesota
southeast into Wisconsin along with a surface trough axis that may
be able to focus some convergence an produce thunderstorms.
Evening activity is going to depend on what happens earlier in the
day, so have kept POPs somewhat generic as even if we can get a
decent complex going earlier in the day, additional storms may
form behind it if enough instability can develop again given the
broader scale environment.

A potent, compact upper level shortwave is expected to move
across the area Saturday evening, which together with some decent
instability and shear produces a risk for severe weather that
evening. At this time the risk seems to be confined to the
afternoon and evening hours with hail and wind the main threat.
Have kept to mainly chance pops with a small area of likely along
the Canadian border. Temperatures to remain on the warm side with
some low 80s southwest to low 70s northeast.

As the shortwave drops southeast of the area Sunday we are
looking at some daytime instability showers and possibly
thunderstorms with little/no severe risk due to the lack of shear.
Temperatures will also be much cooler with afternoon highs only
in the low to mid 70s.

After the shortwave drops to our southeast a large high pressure
ridge moves in and keeps the weather quiet for Sunday night
through early Tuesday, with a gradual warming trend. Precipitation
chances return for the Tuesday afternoon through Thursday time
frame, with enough differences in the models to keep POPs in the
slight chance or chance POP range.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1253 AM CDT Fri Jul 21 2017

Another round of MVFR to IFR fog will develop overnight at some
TAF sites, with BRD and HYR most likely to fall to IFR visibility
at times overnight. A chance for a shower at INL overnight,
otherwise increasing VFR clouds at all sites through the TAF
period. Calm winds overnight becoming generally southeast at 5-10
knots Friday, with a few gusts to near 20 knots at BRD. Exception
will be at DLH where wind direction is expected to shift to more
east-northeasterly in the afternoon.

Confidence in convection on Friday is generally low, with a low
chance for showers or storms throughout the day at BRD, then a
better chance for storms at BRD, DLH, and HYR in the evening hours.
However, it is possible the storms set up south of these sites, so
due to low confidence have only included a VCSH mention until timing
of thunderstorms can be predicted with some level of certainty.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  59  78  58  72 /   0  30  20  30
INL  54  80  59  76 /  40  20  30  60
BRD  62  81  64  83 /  10  40  40  30
HYR  58  82  63  78 /   0  50  40  30
ASX  57  82  58  72 /  10  20  30  30

&&

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

$$

SHORT TERM...WL
LONG TERM...LE
AVIATION...JJM



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