Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 251747 AAC
AFDDLH

Area Forecast Discussion...UPDATED
National Weather Service Duluth MN
1247 PM CDT SAT JUN 25 2016

.UPDATE...
Issued at 1247 PM CDT Sat Jun 25 2016

Very busy morning today with the thunderstorm complex moving
across far northern Minnesota. This was a fairly textbook morning
low level jet/warm-moist advection event, with the elevated activity
riding the area where the LLJ intersected the 925-850 mb
thermal/moisture and CAPE gradient. While the deep updrafts
associated with this MCS have translated well to the east over
central Lk Superior, a low amplitude, but fairly mature meso-high
has developed (likely aided in part by the cold Lk Superior water
temps), and has created a fairly robust northeast surge of surface
winds across the western third of the big lake. Several buoys and
KDYT have been peridoically gusting to above 20-25 knots as a
result. This is still below the threshold for a small craft
advisory, but has vastly increased the risk of RIP currents along
the MN/WI Point beaches this afternoon as 2-3 foot swell continues
to come on shore. We have increased the risk of RIP currents in
the surf zone forecast and also issued a beach hazards statement
as we are right on the cusp between moderate and high risk for RIP
currents.

The other major concern for this afternoon/evening, as has been
well-advertised, is the threat for more severe storms as the
primary upper wave and approaching cold front interact with a very
unstable airmass with sufficient deep layer shear for supercells.
most of the kinematic parameters and dynamic forcing certain
suggest a good probability of at least a few rather high end
storms, with 60-120 meter 12 hour height falls across northern MN
this evening, combined with 40+ knots of deep layer shear and at
least sufficient near surface shear and LCL heights for tornadic
supercells. However, as with the event last Sunday, much of the
evolution and threat levels for the rest of today are conditional
with respect to convective mode. If storms rapidly grow upscale to
a line or MCS, damaging wind gusts and the potential for very
large hail will be the primary threats, but if storm mode can
remain discrete for 2-3 hours, the attendant tornado threat with
the most intense storms/supercells will likely be considerably
higher, in particular in the vicinity of the northward retreating
outflow boundary from the morning MCS that currently lies from
near Duluth to Bigfork as of noon.

&&

.SHORT TERM...(Today through Sunday)
Issued at 300 AM CDT Sat Jun 25 2016

Main concern for short term is severe weather today and this
evening.

Current surface analysis indicates an area of showers and thunderstorms
moving along the international border. This area will continue to
move along the border early this morning. Another area of strong
to severe thunderstorms extends from Warroad to Fosston. This
area of storms should clip the western portion of Koochiching
county in the next hour.

The main focus for the short term is another round of severe
weather this afternoon and this evening across the forecast area.
SPC basically has the entire forecast area in an enhanced area
for severe thunderstorms. The situation today is somewhat similar
to last Sunday`s situation. Forecast CAPE values are a little
lower (3K  vs. 4K ) and the best shear region is
behind the front while it was with the front last Sunday. As
indicated by the day shift...unlike last Sunday...there will not
be as strong as a cap so thunderstorms will develop earlier.
But...like last Sunday...a cold front will move through NE MN this
afternoon and NW WI this evening. Out ahead of of it...dewpoints
will be in the middle 60s to lower 70s. There will be a
possibility of supercells at the beginning of the evening with a
line developing in the late afternoon and evening. Large hail and
damaging winds along with possible tornadoes will be the main
threats with the storms

After the front passes...an area of high pressure will build into
the region late saturday night brining in cooler and drier air for
Sunday. A weak shortwave will move through Northern MN Sunday
afternoon brining a chance for showers.

.LONG TERM...(Sunday night through Friday)
Issued at 300 AM CDT Sat Jun 25 2016

A cut off upper lever low will translate across Ontario through
sunday night. The resulting cyclonic flow, along with much cooler
air, to dive over the western lake superior region Monday. The cold
air aloft will bring tight pressure gradient into the region,
producing gusty northwest winds sunday night through Monday.

Latest guidance suggests temps at 850hPa are on the order of just a
degree or two above zero C with the core of the coldest air that
tracks over the MN arrowhead zones Monday. High Temperatures on
Monday will be well below normal across the region with readings
topping out generally in the 60s. The steep lapse rates and
instability will also result in scattered rain showers during this
time.

Surface high pressure and mid level ridging will build into the
Northland through Mid week, bringing a return to seasonable
temperatures and winds of generally less than 10 kts.

Rain chances return to the forecast late Wednesday through Thursday
as a vort max, with transition to cold air advection, drops out of
canada and tracks over the forecast area. Latest GFS/ECM are in good
agreement that an upper level low deepens over hudson bay through
the end of the week, keeping the western great lakes region in a
cool unstable cyclonic flow as we go into the Holiday weekend.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday morning)
Issued at 1247 PM CDT Sat Jun 25 2016

Mainly MVFR ceilings with some patches of VFR at the start of the
forecast. With the approach of the front, expect thunderstorms to
develop and become numerous late this afternoon. Once the
thunderstorms are underway, mainly VFR ceilings will be found, with
IFR visibilities with the stronger storms. Some hail may occur
with the stronger storms. Gusty surface winds will occur ahead of the
front, in the vicinity of the storms, and diminish behind the front.
Conditions will improve to VFR behind the front by 03Z.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  82  57  78  54 /  80  70  20  10
INL  80  58  69  54 /  80  30  50  10
BRD  85  59  79  56 /  80  20  10   0
HYR  86  59  80  56 /  70  90  10   0
ASX  84  60  80  56 /  70  90  10  10

&&

.DLH Watches/Warnings/Advisories...
WI...Beach Hazards Statement until 8 PM CDT this evening for WIZ001.

MN...Beach Hazards Statement until 8 PM CDT this evening for MNZ037.

LS...None.
&&

$$


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