Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Duluth Minnesota
643 PM CDT Thursday may 28 2015
Short term...(this evening through friday)
issued at 333 PM CDT Thursday may 28 2015
A slow moving cold front will gradually track across north central
this evening...reaching northeast Minnesota late tonight...and
finally passing over northwest Wisconsin through the day Friday.
The timing of the frontal passage continues to slow with
a strengthening SW low level jet. Have adjusted probability of precipitation
tonight/Friday to convey the slower frontal passage timing.
Latest short term guidance suggests the surface front and associated
convection remains confined to north central Minnesota through
midnight...reaching the twin ports/arrowhead around day break
Friday. Meanwhile...a secondary area of showers and storms is
expected to develop out ahead of the front...and lift into
northern Wisconsin late tonight.
NAM/GFS bufr soundings show favorable conditions for periods of
heavy rain overnight/Friday as profiles become deeply saturated
with a few hundred joules of cape and precipitable water values around an inch
and a half. Have increased quantitative precipitation forecast amounts along the cold front...with
the highest amounts expected over northern Wisconsin. Much of the
forecast area will receive rainfall amounts through Friday of a
half inch to one inch with locally higher amounts up to an inch
and a half.
Skies will clear across northeast Minnesota through Friday
afternoon...with gusty northwest winds to 20 miles per hour. The showers and
thunderstorms will persist for locations in Wisconsin through much
of the day Friday.
Long term...(friday night through thursday)
issued at 333 PM CDT Thursday may 28 2015
By Friday evening the cold front will still be moving across
northwestern WI...and be out of the area by midnight. There will
still be enough lift and instability with the frontal passage that showers
and thunderstorms will remain in the forecast.
Looks to be a dry and cool weekend with surface high pressure
building into the region behind the front. Upper levels will feature
a broad ridge of high pressure which will stay in place for most of
the weekend. This is a very cool weather pattern. By Sunday night
the cold air advection will have left some very cold air over the
region...with the forecast models predicting 800 mb temperatures down into the
negative numbers. However...return flow late in the weekend behind
the high will help temperatures rebound to near normal for early in the
week. With the return flow and warm air advection comes a chance of
showers and thunderstorms early in the week when upper level short
waves rotate through the flattening ridge. By midweek the ridge will
have built farther east...while a trough digs into the southwest.
This trough will set the stage for a warmer and wet period at the
end of the week.
Aviation...(for the 00z tafs through 00z Friday evening)
issued at 643 PM CDT Thursday may 28 2015
Low pressure in the eastern Dakotas and a warm front across far
northern Minnesota were combining to produce showers and storms
over eastern North Dakota into northwest Minnesota. The
showers/storms will progress east tonight with other showers
developing in Iowa moving north into portions of northern
Wisconsin later tonight. The low will continue to move east
tonight into Friday dragging a cold front through as well. Showers
and storms should become widespread later tonight into
Friday...then diminish from the north.
Areas of fog and IFR ceilings were occurring around Lake Superior
and a look outside showed the lower clouds not too far off to the
east of kdlh. The east/northeast winds are expected to diminish a
bit more overnight with stronger southwest flow not too far above
the surface. Confidence in whether the stratus and fog will roll
in and remain at kdlh is lower than average tonight. The surface
wind is forecast to go more southerly late tonight which would
support keeping the lower clouds out of kdlh. At this time...we went
with tempo in the taf at kdlh until late then went prevailing IFR.
Most areas will see at least MVFR and possibly IFR ceilings
develop overnight into Friday morning.
Some of the storms this evening at kinl could be quite strong and
produce a period of strong winds and some hail.
Preliminary point temps/pops...
dlh 49 67 41 58 / 50 80 0 0
inl 48 61 35 58 / 80 20 0 0
brd 58 65 41 62 / 70 80 0 0
hyr 59 72 42 61 / 70 90 20 0
asx 54 69 41 57 / 50 90 10 0
Ls...Small Craft Advisory until 7 PM CDT this evening for lsz143>147.