Area Forecast Discussion
Issued by NWS Duluth, MN

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800
FXUS63 KDLH 202100
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
400 PM CDT Thu Jul 20 2017

.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 18Z TAFS through 18Z Friday afternoon)
Issued at 1254 PM CDT Thu Jul 20 2017

VFR conditions as of issuance time expected to continue until at
least 06z tonight. Some weak thunderstorms over NW MN are expected
to slowly, slowly drift east this afternoon, but are weakening
with time and are not currently expected to reach KINL or other
terminals. This may change in the next few hours so will be
monitoring for possible updates. MVFR fog is possible in the 08z-
12z time range for KHIB, KDLH, KBRD and KHYR, so have included
TEMPO groups for these sites. After 12z a return to VFR is
expected. Thunderstorms expected to develop in the 15z-18z time
range for KINL and/or KBRD, but confidence in location and timing
is low at this time and have left out for now.


&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  59  78  59  71 /   0  20  20  40
INL  54  80  59  74 /  10  20  40  60
BRD  62  81  63  81 /   0  40  30  30
HYR  55  81  62  78 /   0  30  30  30
ASX  55  80  58  73 /   0  20  20  30

&&

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

$$

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



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