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Area forecast discussion
National Weather Service Duluth Minnesota
335 PM CDT Mon Aug 19 2019

Short term...(this evening through Tuesday night)
issued at 336 PM CDT Mon Aug 19 2019

A cold front will approach from the north tonight with scattered
showers and storms developing along and ahead of the front,
lingering through the day Tuesday. The cold front then exits from
north to south on Tuesday afternoon leading to clear skies and below
normal temperatures for Tuesday night. Total precipitation amounts
will vary, and not all locations are expected to experience
precipitation. There is a very low chance for a few strong to severe
storms being possible in north-central Minnesota this evening, but
generally storms are not anticipated to be severe.

On the synoptic scale a fairly zonal flow pattern exists across the
Canadian prairie, the northern Great Plains, and the upper Midwest.
At low levels a weak cold front is moving south across southern
Manitoba, tracking southeast towards the Northland tonight into
Tuesday. While the area of high pressure behind the front will bring
cool and dry air to the region, along and ahead of the front showers
and storms are expected. Specifically, across the central and
northern Great Plains rich low level moisture is surging northward,
evident even in the visible satellite imagery as stratus advects
across the Missouri River valley in South Dakota. While the
mid/upper level is generally zonal, a weak mid-level impulse will
move across southern Saskatchewan towards North Dakota this evening.
The strong warm air advection combined with the weak approaching
impulse will result in relatively strong broad-scale lift across the
eastern Dakotas, with an elevated mixed layer with steep mid level
lapse rates also advecting into this area. While capping should
prevent any surface-based storms from developing this afternoon,
this evening an increasing low level jet is expected to kick off
scattered to widespread thunderstorms across the eastern Dakotas.
These storms will then track eastward late tonight into early
Tuesday morning, possibly in two clusters - one along the actual
cold front near the international border and another cluster moving
across central Minnesota. These storms could be capable of producing
severe weather given around 2000 j/kg MUCAPE and 40-50 knots of deep-
layer shear, mainly in the form of speed shear. The main threat from
the strongest storms will be large hail given the elevated nature of
the storms, with the best chance for severe storms across north-
central Minnesota.

As storms evolve east-southeastward and the cold front moves from
north to south, showers and storms will linger into Tuesday morning.
It is uncertain if storms will maintain their momentum after moving
out of a better low level wind field on Tuesday morning, but there
will remain both rich low level moisture and probably a decent eml
to support convection if any is ongoing. The most likely scenario is
that storms will fizzle out as they move into northeast Minnesota
Tuesday morning and transition to more showers with embedded thunder
as they get into northwest Wisconsin Tuesday afternoon, but there is
a chance storms can sustain and remain strong, producing lightning
and heavy rain across much of the Northland. This probability is
low, but given the trends observed in both model guidance and
current surface observations, the environment may support storms
lasting well through the morning hours.

On Tuesday afternoon, assuming the morning storms eventually fizzle
out, there may be a second round of showers and storms that develop
ahead of the cold front as it moves from north to south through
northeast Minnesota and into northwest Wisconsin, resulting in
isolated showers/storms through Tuesday afternoon in northwest
Wisconsin. These storms would likely not be severe. Otherwise skies
will already begin clearing out of north-central Minnesota by mid
afternoon, clearing out across the rest of the Northland by the late
evening hours. Highs Tuesday will range from the low 70s in north-
central Minnesota to the upper 70s to near 80 in northwest
Wisconsin. Lows Tuesday night in the 40s to low 50s.

Long term...(wednesday through monday)
issued at 336 PM CDT Mon Aug 19 2019

Quiet conditions will be in place for the first part of the extended
before turning more active for the weekend. High pressure will build
in across the upper Midwest for Wednesday and Thursday bringing
clear skies and highs in the upper 60s and lower 70s. The high will
then shift to the east on Friday setting up southerly flow across
the Northland. This will bring in some warmer air along with an
increase in moisture ahead of a shortwave trough moving into the
northern plains. The European model (ecmwf) is much more organized with this trough
with an upper low moving into eastern Saskatchewan and western
Manitoba. Rainfall from this trough is expected to hold off until
Friday night or early Saturday morning, mainly for western areas.
This wave doesn't look to move across the Northland as the upper
level support weakens and leaves a boundary draped across the
region. This will keep chances for showers and storms in place for
Saturday and Sunday. Models diverge for the weekend with the GFS
keeping zonal flow in place while the European model (ecmwf) transitions from
northwest flow to southwest flow. With southwest flow persisting at
the surface, this will keep the flow of moisture in place. Questions
remain this far out as to the mesoscale and thermodynamic features
that will be be in place for the weekend, but there are hints that
some strong or severe storms may be possible at some point,
especially if timing of energy aloft lines up favorably with daytime
heating. Highs for the weekend will be in the 70s.


Aviation...(for the 18z tafs through 18z Tuesday afternoon)
issued at 1247 PM CDT Mon Aug 19 2019

VFR conditions will continue into tonight with mainly clear skies.
Gusty southwest winds will persist through the afternoon before
diminishing around sunset. A cold front will begin to approach
from the west late tonight/early tomorrow morning, bringing MVFR
ceilings along with showers and thunderstorms that will spread
from west to east starting just before sunrise and continuing
through the morning. There may also be a brief period of MVFR or
worse fog at khib prior to the rain, but that will be highly
dependent on the timing of the rainfall. There is a small threat
of a brief period of low level wind shear at kinl around sunrise as well.
Conditions may deteriorate to IFR or worse within any storms and
timing of this threat will be further refined in future issuances.


issued at 336 PM CDT Mon Aug 19 2019

Winds will quickly diminish this evening after sunset becoming 5 to
10 knots from the southwest overnight and into Tuesday morning. A
front will then push through around midday that will bring showers
and storms along with a wind shift to the northwest at 6 to 12
knots. A few of the storms may be strong with gusty winds and small
hail. Northwest winds will then continue on Wednesday at 6 to 12
knots with a few gusts to around 15 knots. Waves will be 2 feet or
less through the period outside of any thunderstorms.


Preliminary point temps/pops...
dlh 60 77 51 72 / 10 60 0 0
inl 56 72 44 68 / 80 90 0 0
brd 62 78 50 74 / 10 60 0 0
hyr 56 79 50 74 / 0 50 30 0
asx 58 80 54 74 / 0 40 30 0


Dlh watches/warnings/advisories...
Ls...Small Craft Advisory until 7 PM CDT this evening for lsz140>143.



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