Area Forecast Discussion
Issued by NWS Duluth, MN
FXUS63 KDLH 221750 AAB
Area Forecast Discussion...UPDATED
National Weather Service Duluth MN
1250 PM CDT FRI JUL 22 2016
Issued at 1250 PM CDT Fri Jul 22 2016
A fairly tranquil weather day today, for a change, as weak high
pressure and west-northwest winds have temporarily displaced the
high theta-e boundary layer airmass just off to our south today.
Still, with full sunshine, a rather hot afternoon is in store for
many areas with highs reaching the mid 80s across northern MN and
upper 80s/lower 90s over the southern CWA, and even with the lower
dewpoints today, it will still feel somewhat muggy this afternoon
as wet ground and lush growing vegetation aid efficient evapo-
transpiration. The current forecast through this evening appears
to be on track, and the only changes were very minor.
For tonight, we are becoming a bit more concerned that some
thunderstorm activity or the northeast fringe of a
nocturnal/morning MCS may affect the southwest portion of our CWA
tonight/Sat morning as the northern CAPE gradient begins migrating
back northward. This may be complicated even further by the
evolution of the developing/ongoing convective cluster northwest
of aberdeen, SD. We have raised PoPs a bit in these areas after
midnight and Sat morning. If this were to occur, it would also
likely result in lots of additional complexity to the
afternoon/evening convective initiation and evolution tomorrow,
making an already difficult forecast even harder.
.SHORT TERM...(Today through Saturday)
Issued at 353 AM CDT Fri Jul 22 2016
Another day of above-normal temperatures today but not as humid the
past few days. Sunny skies today due to high pressure building in
across the upper Midwest, then increasing clouds late tonight into
Saturday as a warm front lifts north into the region. A chance for
showers and thunderstorms during the afternoon, with storms likely
in the evening.
High pressure building in across southern Canada, stretching
southeast across the Midwest behind the cold front that moved
through yesterday. While there will not be much in the way of heat
relief - 850mb temps in the 16-21C range today - the cold front has
cleared out the low 70s dew points that were prevalent across
northwest Wisconsin yesterday, and dew points are generally expected
to continue to lower today in the northwest flow. Upstream dew
points are in the upper 50s to low 60s, and through the afternoon
those kinds of dew points are expected across northeast Minnesota.
Highs today will be in the upper 80s to low 90s - fairly similar to
yesterday. Breezy northwest winds across the MN Arrowhead and along
the south shore of Lake Superior as sunny skies will lead to deep
mixing, perhaps as high as 700mb, resulting in gusts to 20-30mph in
the afternoon. Outside of the arrowhead weaker northwest winds can
be expected as winds aloft are not as strong.
Clear skies this evening, with increasing high-level clouds from
west to east across north-central Minnesota due to late day
convection expected across the eastern Dakotas. High pressure
centered over central Manitoba will move east into northwest Ontario
resulting in light/variable winds overnights gradually becoming
easterly by Saturday morning. Temperatures will fall to the low to
mid 60s, with some locations across northeast Minnesota and
especially northern parts of the Arrowhead may fall to the upper
On Saturday light east to southeast winds combined with some high-
level clouds will result in slightly cooler temperatures - highs
only in the low to mid 80s with low to mid 70s along the Lake
Superior shoreline and surrounding areas. However, low level
moisture will be on the increase as a warm front rapidly advances
north through Minnesota and Wisconsin, resulting in dew point values
approaching the low 70s in the Brainerd Lakes/Lake Mille Lacs area
in the afternoon. Isolated showers and storms are possible by the
early afternoon across north-central to east central MN, with higher
confidence in mid to late-afternoon scattered to widespread
thunderstorms moving into this area, with storms expanding into
northeast Minnesota and northwest Wisconsin. These storms will be
strong to severe, especially if early-day activity does not
materialize. Moderate to extreme instability will develop by late
day with 2500-4000 j/kg MUCAPE along and behind the warm front which
is expected to be along the Highway 2 corridor by 00z. Wind profiles
are favorable for sustaining organized clusters with 25-35 knots of
deep-layer shear present along and behind the warm front, with a
north-northeast storm motion of 20-30mph. With such a warm airmass
still in place (despite the cooler high temps), 0c height of 14-
15kft AGL will result in less of a hail threat with these storms.
.LONG TERM...(Saturday night through Thursday)
Issued at 353 AM CDT Fri Jul 22 2016
Saturday night looks like another active night across the forecast
area, with the surface low over southern Manitoba with a cold front
slowly advancing across Minnesota during the evening. A very warm
and unstable airmass will have been pulled up into the region ahead
of the cold front, and will ride up over a leading warm front
extending east to northwest Wisconsin just south of Lake Superior.
Between the instability and the shear parameters, we are looking at
another round of severe weather during the afternoon and evening.
Have increased pops through the period and refined the timing
somewhat. The front sweeps far enough east early Sunday morning to
bring the precipitation to an end. Showers and a few thunderstorms
may affect the area in the west-northwest cold air advection on the
southwest side of the low, with precipitation chances limited to
along the Canadian border.
Sunday and Monday the heat and thunderstorm chances let up somewhat,
with highs by Sunday in the mid 70s and low 80s, warming only
slightly for Monday.
Large model differences bring more uncertainty to the forecast by
mid week, with fairly fast zonal flow with some fast moving
shortwaves within it. Each of the models have some fairly
significant placement and timing differences, so have kept some
small precipitation chances in the forecast Tuesday through Friday.
Temperatures will be near to slightly above normal during this time
.AVIATION...(For the 18Z TAFS through 18Z Saturday)
Issued at 1250 pm CDT Fri Jul 22 2016
The clear skies and VFR conditions across the Northland today
will continue through this evening. There is a possibility of fog
late tonight considering the negligible wind flow tonight...but
modeled surface humidity and GFS/NAM MOS guidance is not
suggesting fog. Therefore...kept it out at this time.
There will also be an increasing chance of showers and storms from
the southwest Saturday morning. The KBRD area has a good chance of
showers by the late morning...but held off on thunder at this time
due to excessive uncertainty.
.PRELIMINARY POINT TEMPS/POPS...
DLH 88 63 79 62 / 0 0 70 80
INL 86 60 82 62 / 0 0 60 80
BRD 90 66 84 65 / 10 20 70 70
HYR 90 63 87 66 / 10 10 70 80
ASX 92 63 82 64 / 0 0 60 70