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Area forecast discussion...updated 
National Weather Service Duluth Minnesota
1230 PM CDT sun Jul 5 2015

issued at 1230 PM CDT sun Jul 5 2015

Updated 18z aviation discussion below...


Short term...(today through monday)
issued at 324 am CDT sun Jul 5 2015

A decaying mesoscale convective system was affecting the northwest corner of the forecast area at
0730z. Thunderstorms were trying to form ahead of the mesoscale convective system in an axis
of MUCAPE of 500 j/kg. the storms attempted to move
eastward...they are encountering drier air that has been locked in
place for the last few days and decaying. The high pressure that had
been in charge was drifting off to the eastern Great Lakes while a
surface trough was following behind the mesoscale convective system into northwest Minnesota. This trough will
move little today and be the foci for additional storm development
through the day. There will be a brief break in the action this
morning after the mesoscale convective system has run its course. But by afternoon...a
parade of short wave energy will begin to eject out ahead of a
closed upper low moving through central Canada. Moisture will
increase ahead of the trough due to a low level jet moving through the area
with warm 850 mb temperatures which will reach to near 18c by 00z Monday.
The storms that do form will have periods of heavy rain with some
hail near the stronger storms near the Canadian border. The warm
temperatures will reduce the hail size farther away from the border.

Tonight finds a long wave trough moving into Minnesota as a deepening surface low
moves up the trough into central Minnesota by 12z Monday. Precipitable waters will approach
2 inches across much of the area by 12z Monday. Ingredients are
coming together for a prolonged heavy rain event after 06z. Have a
mention of heavy rain coinciding with the upper level divergence maximum
that separates Minnesota from WI by 12z. Several spots could see 1 to 1.5
inches of rain. Because it has been dry lately...not expecting any
flooding as rivers are running a bit below normal and flash flood
guidance values are around 2 inches in one hour. Will likely see
ponding of water on roadways and culverts filling up.

On Monday...the surface low lifts into northwest Ontario by 00z Tuesday. The
best instability will occur ahead of the surface low in northwest WI and areas
adjacent to Lake Superior in the morning for a thunder mention.
Further to the west...have removed the thunder mention but kept in
the moderate rain. By afternoon...the instability has weakened
considerably as the surface low pulls farther away. Have a mention of
thunder in the far eastern edge of the WI forecast area with just
rain elsewhere. High pressure begins to build across the rest of the
region in the afternoon.

Long term...(monday night through saturday)
issued at 324 am CDT sun Jul 5 2015

A warming trend through the work week with precipitation chances middle-
week into the weekend. Following a strong cold frontal passage on
Sunday night into Monday an area of high pressure will descend out
of southern Canada leading to cooler weather. At the upper levels a
weak middle-level ridge will give way to a more zonal pattern Tuesday.
A weak upper level trough axis swings through Wednesday into
Thursday...which along with a baroclinic zone across western Ontario
into northern Minnesota could lead to showers/storms. A better
chance for precipitation will occur late in the week into the
weekend when a weak front dips south into the region. Instability
looks to be best on Saturday...though it looks like very weak winds
aloft which would prevent widespread organized convection.


Aviation...(for the 18z tafs through 18z Monday afternoon)
issued at 1230 PM CDT sun Jul 5 2015

Continuing to monitor thunderstorm development over northwest Minnesota
early this afternoon. Mesoscale convective system is expected to move eastward through NC
and into NE Minnesota this afternoon/early evening. Additional
thunderstorm development is likely south of the thunderstorm
complex. Maintained general trends from previous forecast and
refined storm impacts at inl/hib. Confidence decreases at
brd/dlh/hyr as additional development will be required for storms
to affect those terminals. Generally VFR/MVFR ceilings and visibilities
expected...except when thunderstorms pass through. Have seen visibilities
as low as 1/4 sm in eastern North Dakota this morning...and
believe low visibilities are likely at inl as storms pass through. Have
reflected timing in tempo group there. Also carrying a period of
IFR visibilities at brd with rain and storms...transitioning to fog/mist
after precipitation ends. Much less confident in very low visibilities at
remaining terminals and will update through the afternoon as
necessary. Rain and thunderstorms will end overnight for all but
hyr...where showers may linger through Monday morning. Expect a
period of MVFR/IFR ceilings and visibilities overnight for sites which
receive rainfall.


Preliminary point temps/pops...
dlh 82 65 71 50 / 40 90 100 10
inl 79 58 68 46 / 70 70 30 10
brd 86 65 73 50 / 70 90 80 10
hyr 83 68 73 51 / 10 90 100 20
asx 84 67 72 53 / 10 80 100 20


Dlh watches/warnings/advisories...


Short term...gsf
long term...jjm

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