Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 271728
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1228 PM CDT Tue Jun 27 2017

.SHORT TERM...(Today through Wednesday)
Issued at 314 AM CDT Tue Jun 27 2017

As of 08z this morning, temperatures have dropped quite a bit,
thanks to light winds and mostly clear skies across the area,
enhancing radiational cooling. This has led to some patchy fog
developing for some locations. For example, KFOZ near Big Fork has
already dropped to 2SM earlier this morning, with KHIB down to 1SM
as well. Due to temperatures falling quicker than expected, and
radiational cooling conditions expected to continue for the next few
hours, decided to put in some patchy fog for this morning, which
should quickly burn off by 13z later this morning.

The rest of today looks to be dry and more seasonal compared to the
last several days. High temperatures today should rise into the
lower to mid 70s across the Northland, which is right around
seasonal averages. Sfc high pressure and mid-level ridging will
remain in control through the day, with some high clouds expected,
as indicated by model soundings. The sfc high pressure will move off
to the east later this morning and afternoon, which will turn our
winds more from the south, enhancing warm air advection. Chances of
showers and thunderstorms will increase from west to east as a mid-
to upper-level system moves in from the Intermountain West states.
Broad upper-level divergence will increase Wednesday morning along
with 850-700 mb layer warm air advection. This will set the stage
for a damp Wednesday. Low-level moisture transport will be enhanced,
thanks to a strengthening low-level jet, which will increase 850 mb
theta-e advection. Sfc dew point temperatures are forecast to be in
the upper 50s and lower 60s across much of the Northland, especially
in the afternoon and early evening. Pwat values from the NAM and GFS
models are progged in the 1.2 to 1.5" range, so there could be some
heavy rainfall potential with this system. Analysis of the latest
run of the NAEFS mean Pwat climatological percentiles indicate these
values could reach into the 90 to 97 percentile at 18z Wednesday, so
well above the climatological mean. This would indicate that some
flash flooding is possible in the heaviest rainfall.

As far as severe potential is concerned, the general consensus
between the synoptic models is that the axis of the best instability
will be off to the west over eastern ND/western MN, with perhaps
some of the better instability just reaching into our far western
counties by Wednesday afternoon. MLCAPE values are generally up to
800 J/kg around the Brainerd Lakes region, with weak 0-6km bulk
shear values of 20 to 25 kts. This appears to be a more favorable
scenario for heavy rainfall and flooding than for severe storms due
the best instability staying to the west. Accordingly, the Storm
Prediction Center`s latest Day 1 convective outlook has shifted any
notable severe weather risk to the west, but keeping much of the
Northland in the general risk of thunder. Same for the Day 2
outlook, with only a small sliver of northwest Wisconsin in the
Marginal Risk. The better axis of instability looks to remain to the
south over southern Minnesota and Iowa.

Easterly flow off of Lake Superior will help to keep temperatures
along the lake a bit cooler, with highs in the lower 60s over
adjacent areas of the lake, and into the upper 60s and lower 70s
further inland.

.LONG TERM...(Wednesday night through Monday)
Issued at 314 AM CDT Tue Jun 27 2017

The area of low pressure that brought the rain during the day
Wednesday will move northeast into the northern great lakes by
Thursday morning.  The main batch of the precipitation will end west
to east across the forecast area late Wednesday night. However, the
atmosphere will remain unstable on Thursday as a shortwave moves
along the International Border bringing a chance for thunderstorms
across the north Thursday afternoon.

A stronger shortwave will move through MN and WI Thursday night
through Friday night.  Another round of showers and thunderstorms
will develop across the region by early Friday morning and continue
into early Saturday morning.  Another shortwave will affect the
region on Saturday bringing a chance for showers/thunderstorms.
There will be a break Saturday night and Sunday morning before
another possibility of showers and thunderstorms will occur Sunday
afternoon and evening.  There may be some precipitation along the
International Border on Monday. The outlook for July 4th looks to
be dry at the moment.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1226 PM CDT Tue Jun 27 2017

An elongated area of low pressure will move eastward across the
region overnight and into Wednesday. Moisture surging northward
ahead of the low pressure system and frontal boundary will help to
initiate numerous showers and thunderstorms late tonight and
especially on Wednesday. VFR conditions today will give way to
MVFR and eventually IFR CIG`s and VSBY`s on Wednesday.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  73  54  62  54 /  10  50  90  40
INL  75  55  67  55 /  10  60  80  50
BRD  75  58  71  57 /  10  80  80  40
HYR  75  56  69  56 /   0  60  90  50
ASX  76  55  67  53 /   0  40  90  60

&&

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

$$

SHORT TERM...JTS
LONG TERM...Stewart
AVIATION...DAP



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