Area Forecast Discussion
Issued by NWS Duluth, MN

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806
FXUS63 KDLH 281508 AAB
AFDDLH

Area Forecast Discussion...UPDATED
National Weather Service Duluth MN
1008 AM CDT SUN AUG 28 2016

.UPDATE...
Issued at 1008 AM CDT Sun Aug 28 2016

Things have evolved pretty much according to plan in the wake of
the departing wave from last night. The primary push in the low
levels has been to the east, leaving a nearly saturated low level
airmass in place across the DLH CWA, and the surface-850 frontal
zone nearly stationary from southeast ND into southern MN this
morning. A modest southwesterly low level jet and associated
mesoscale frontogenesis forcing for ascent has continued to
support additional thunderstorm development overnight and this
morning within the frontal zone from the eastern Dakotas into
southern MN. Meanwhile, north of the front, most of the DLH CWA is
in light flow beneath a very shallow/saturated inversion (per the
12z INL sounding), with persistent areas of fog.

Low level flow is already responding to the next approaching
system on the northern high plains, and low level warm/moist
advection should do nothing but continue to slowly increase as
today progresses. Abundant sunshine in the warm sector should
allow for large CAPE values to the south of the warm front by this
evening. Hi-Res and CAM guidance is all over the place on timing
and placement for TStorm development, not only from model to model
but from run to run - to the point that it is almost worthless.
Looking at the large scale mass fields and evolution of the large
scale forcing depicted by the synoptic models, the warm frontal
zone should lift slowly northward this afternoon, with advective
processes and mass influx becoming maximized late this
afternoon/evening over northwest MN, where we expect convective
initiation to occur sometime in the 22-02z time frame. These
storms should then translate east/southeastward along the warm
front overnight across much of the DLH CWA. Updates to reflect
current trends, including low pops for convective debris across
the south, and a slower clearing trend are already available.

&&

.SHORT TERM...(Today through Monday)
Issued at 317 AM CDT Sun Aug 28 2016

The vigorous upper level trof was moving through the Arrowhead at
07Z/2am. Meanwhile, at the surface, high pressure covered the
forecast area with plenty of stratus and patchy fog. A thunderstorm
complex has developed in northeast South Dakota which is on the nose
of a low level jet moving through eastern South Dakota and into west
central Minnesota. This complex is also on the leading edge of an
area of positive vorticity advection as the next short wave is
moving through the central Dakotas. At this time, the track of the
storms takes it into the Brainerd lakes area by 10Z/5am. Have
adjusted pops accordingly to account for this complex. The latest
short term hires model guidance, particularly the HRRR, has this
complex lingering/expanding around the Brainerd lakes until early
afternoon, expanding toward the I35 corridor. The NAM does not pick
up on this at all, while the GFS and ECMWF do. These models have the
complex staying in west central Minnesota through the morning before
decaying. Leaned more toward the HRRR, but will mention to the next
shift about the GFS/ECMWF solution. Elsewhere, with upper ridging
building across the region, no rain is expected.

Model solutions vary widely with the evolution of the next round of
storms to affect the area tonight. The NAM has an MCS plowing
through northern Minnesota, the GFS has storms over the northern
third of the area, the GEM hints at something developing in central
Minnesota, the ECMWF has a complex of storms from eastern North
Dakota to the Twin Ports before 06Z/1am. Leaned away from the NAM
and GEM and used a blend of the GFS/ECMWF for pops. These storms
will form on the nose of the level jet moving into Minnesota as a
potent vorticity max moves quickly into Minnesota on the fast
westerly flow aloft. There is a potential for some of the storms to
be strong to severe overnight as shear increases, as does lapse
rates, and MUCAPE ranges from 1500 to 3000 J/kg. This is in response
to the low level jet/vorticity max moving eastward over the area,
and an approaching cold front.

Thunderstorms will continue on Monday as the cold front moves into
the region by Monday afternoon. Will have the highest pops along and
on either side of the cold front. Severe is possible again on
Monday, but due to ongoing storms from Sunday night, this may limit
the amount of instability available for severe to form.

.LONG TERM...(Monday night through Saturday)
Issued at 317 AM CDT Sun Aug 28 2016

A stormy and warm start to the work week Monday will be followed by
sunny and seasonable days through the rest of the work week. Chances
for storms return late Friday into Saturday. Highs in the low to mid
70s each day, except for across the tip of the MN Arrowhead where
highs will be a bit cooler in the upper 60s. Overnight lows likely
coolest Tuesday night with lows in the 40s to low 50s, otherwise in
the 50s most nights.

On the synoptic scale the extended period will be dominated by a mid-
level longwave ridge across the Plains/Canadian Prairie mid-week
resulting in broad area of high pressure building mid to late week.
This area of high pressure builds to the east towards the lower
Great Lakes by Friday with a zonal to west-southwest flow developing
aloft, setting the stage for a number of embedded mid-level
disturbances to move across the northern Plains into the upper
Midwest for the weekend.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 656 AM CDT Sun Aug 28 2016

LIFR ceilings and visibilities will rapidly improve to VFR this
morning. Light rain possible at BRD but otherwise dry with a light
south to south-southeast wind at less than 10 knots today.
Tonight, especially around and after midnight, scattered strong
storms are expected to develop and spread across the region. At
this point it seems like storms would develop in north-central
Minnesota and spread east-southeastward towards Monday morning,
possibly impacting all terminals. MVFR ceilings and visibilities
will be possible along with the storms, with fog possible towards
Monday morning.


&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  77  62  83  57 /  20  60  60  40
INL  79  63  81  51 /  30  60  40  10
BRD  80  66  82  57 /  40  50  40  20
HYR  78  63  81  59 /  40  60  40  60
ASX  79  62  84  61 /  20  60  40  60

&&

.DLH Watches/Warnings/Advisories...
WI...None.
MN...None.
LS...None.
&&

$$



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