Area Forecast Discussion
Issued by NWS Duluth, MN
FXUS63 KDLH 190533 AAA
Area Forecast Discussion...UPDATED
National Weather Service Duluth MN
1233 AM CDT SUN JUN 19 2016
Issued at 956 PM CDT Sat Jun 18 2016
Scattered to at times numerous showers and thunderstorms have been
occurring over portions of the Iron Range and Arrowhead this
evening. There was also some brief showers/storms east of Siren to
south of Minong earlier, but that was short lived. The trend has
been for weaker showers/storms and fewer of them. There could be
an increase late this evening through 2 am over far northern
Minnesota as the low level jet increases over the warm frontal
boundary that extended from northern South Dakota through central
Minnesota into Lake Superior. The CAMs have been doing an OK job
this evening and are showing an overall decrease in coverage by or
shortly after midnight. Attention then turns to more storms that
will move in from the west late tonight. Severe storms were
occurring over northeast Montana into Saskatchewan this evening.
This activity is forecast to continue east and possibly impacting
northern Minnesota. The latest NAM keeps the bulk of the storms
north of the International Border tonight into Sunday morning but
several of the CAMs bring it into north central Minnesota after
11Z, continuing east through the Boundary Waters and Arrowhead.
There are still indications storms will extend into our southern
CWA and we kept the mention there as well. Strong winds and heavy
rain will be the main threats late tonight/Sunday morning.
.SHORT TERM...(This evening through Sunday)
Issued at 350 PM CDT Sat Jun 18 2016
Surface obs at mid afternoon suggest that the ever-so-slowly
strengthening surface warm frontal zone lines roughly from
Ashland, to somewhere near Lake Mille Lacs/Brainerd, to south of
Fargo, and has not moved too much from this position most of the
day. Despite continued slow destabilization and a few attempts at
convective initiation per the KDLH radar, storms thus far have not
been able to initiate. There continues to be robust boundary layer
cumulus beneath the mid level cloud deck where there are breaks in
the mid level clouds, so we still expect at least some activity
over the next 3-6 hours. However, if nothing forms by 6-7 PM, it
will likely have to wait until after 10 PM when the low level jet
begins strengthening warm/moist advection.
The first of a couple of main shows should move into the northwest
CWA very late tonight as a strong/severe MCS rolls eastward along
the Canadian border from the Dakotas into northern Minnesota.
There continues to be disagreement between the operational
deterministic and hi-res/CAM/ensemble runs on the specific
placement and timing, but attempting to integrate all of this
information suggests that sometime between 10-14z would be the
initial window, then progressing across the Boundary Waters and MN
Arrowhead for the rest of the morning. However, the north-south
spread on placement is large, with some guidance keeping the MCS
entirely in Canada, and at least 2 CAMs suggesting the southern
flank as far south as the Brainerd area. We have kept the highest
PoPs across the far north, but retained at least low PoPs all the
way to our southern CWA border to account for this uncertainty.
Where ever the MCS tracks, it will likely contain a fairly high
threat of damaging wind gusts and heavy rain.
Additional severe storms should initiate late afternoon Sunday
along/ahead of the cold front in an environment characterized by
4000+ CAPE and 40-60 knots of deep layer shear. Low level shear
appears to weaken rather markedly during the afternoon as the axis
of the LLJ translates to north of Lk Superior, so the tornado
threat may be somewhat minimized, although with such extreme
instability and a boundary around, the tornado threat will
certainly be non-zero. However, the primary threats appear to be
very large hail (perhaps up to baseballs), damaging wind gusts,
and the threat for heavy rainfall with precip water values
pushing 2 inches.
.LONG TERM...(Sunday night through Saturday)
Issued at 350 PM CDT Sat Jun 18 2016
A cold front will move across the Northland on Sunday night,
bringing with it strong to severe thunderstorms. The main focus
will be on very large hail, along with the potential for damaging
winds. Extreme instability in the vicinity of the front will
combine with favorable shear, and forcing from the front, to bring
about a rapid increase in thunderstorm activity by Sunday evening.
The storms will then move east of the CWA by late Sunday Night,
with drier westerly winds moving in behind the front Sunday Night
and Monday. There could be a few showers or thunderstorms across
the north on Monday and Monday evening, but overall it is looking
drier across the CWA than it did in previous runs. In general it
is looking mainly dry from Monday into Wednesday of next week. The
models only hint at very spotty QPF, so wouldn`t rule out a few
very isolated showers and storms during a few of the afternoon
periods. Don`t feel there is enough of a chance at this point to
include in the long term. The picture is less clear for the last
half of the work week and early next weekend. The GFS is most
aggressive in bringing a shortwave through the Northland Thursday
and Thursday Night, while the ECMWF is generally dry. High
temperatures throughout the period are expected to be in the 70s
to around 80. Lows will range from the 40s to around 60.
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1232 AM CDT Sun Jun 19 2016
a warm front stretched from North Dakota east into northern
Minnesota late this evening and will continue to lift north
overnight. A low level jet will develop overnight and may cause some
additional showers and thunderstorms to form, mainly along and
north of Highway 2. Fog will be possible again, but we do not
expect it to be as widespread as Friday night. A complex of strong
to severe storms over northwest North Dakota and southeast
Saskatchewan will continue to move east overnight making it into
KINL around or shortly after 11Z. These storms will continue east
through the morning and will be capable of producing strong winds.
The storms may stretch further south but we limited the mention to
KINL at this time.
A cold front will then be the focus for more storms Sunday afternoon
into Sunday evening and these storms could be quite strong producing
large hail, damaging winds, and frequent lightning.
.PRELIMINARY POINT TEMPS/POPS...
DLH 62 87 60 75 / 40 60 60 10
INL 58 84 56 71 / 60 70 20 10
BRD 66 91 61 77 / 40 50 50 10
HYR 66 86 62 79 / 50 50 60 10
ASX 62 83 61 76 / 50 50 60 0