Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Duluth Minnesota
634 am CDT Monday Sep 1 2014
Short term...(today through tuesday)
issued at 318 am CDT Monday Sep 1 2014
Short term adjustments for timing exit of cold front and
associated precipitation this morning. Lingering showers/isolated storms
will be confined to the eastern tip of the Minnesota arrowhead...and
areas in northern Wisconsin through the noon hour.
Current radar imagery shows widespread rain with embedded thunder
extending from the tip of the minn arrowhead...south over Lake
Superior...and across northern Wisconsin into east-central Minnesota.
Rainfall amounts vary greatly due to the scattered nature of the
convection. As of 300 am...radar estimated rainfall totals ranged
from generally 1/2 to 1" over much of northern Wisconsin...with some
locals receiving in excess of 2". The greatest rainfall was found
over northern Bayfield County...Washburn County...and southern
Sawyer County. Most of NE minn has received a tenth to a half inch
of rain since Sunday afternoon. The greatest totals in Minnesota were
around an inch...and found in the Aitkin/Mille Lacs area...as well
as over portions of the Minnesota arrowhead. At this time...the Duluth
Airport has been missed by the stronger storms and has reported
less than a tenth of an inch.
A drier airmass...with falling 850 mb temperatures...will settle over the
region today in the wake of the exiting cold front. The increased
lapse rates will promote afternoon mixing to around 800
mb...resulting in gusty west-northwest winds 15-20 knots...and dew
points falling into the 40s. Have lowered minimum relative humidity values to
around 40-45% in most areas today. A few locations...mainly across
the Iron Range/Chippewa National Forest may seeing afternoon relative humidity
values in the upper 30s.
Have kept broadbrush 20 probability of precipitation for a stray shower/thunderstorm overnight as
the forecast area remains under a weak cyclonic flow...with
embedded short waves and increasing moisture.
Long term...(tuesday night through sunday)
issued at 318 am CDT Monday Sep 1 2014
A zonal upper level flow will exist over the Northland early in the
period with a trough over the Pacific northwest. This trough will
then move east toward the Northland middle to late week. An area of
surface low pressure and cold front will also move along with the
trough through the region. Several shortwaves will move through the
mainly zonal flow prior to the stronger troughs arrival. We have
several periods of probability of precipitation then increase them quite a bit middle week.
Warm air advection/moisture advection will strengthen Wednesday/Wednesday night as
the flow backs ahead of the upper trough. Precipitable water values are forecast
to rise to 1 to 1.6 inches across our County Warning Area by 00z Thursday. The
stability is also forecast to drop Wednesday and remain quite
unstable into Thursday ahead of the cold front. Showers and storms
will become likely Wednesday night into Thursday morning as the
surface low and upper wave move into the Northland.
Forcing...stability and shear all support a threat for strong to
severe storms Wednesday night into Thursday. The cold front should
move into our eastern zones by 00z Friday...then clear the area during
the late evening hours.
There will be a chance for showers Friday with colder temperatures aloft
and an upper wave passing through...then we have a dry forecast for
Highs Wednesday/Thursday will be in the seventies to around
80...then drop into 60s for Friday through Sunday.
Aviation...(for the 12z tafs through 12z Tuesday morning)
issued at 632 am CDT Monday Sep 1 2014
A cold front stretched from The Arrowhead of Minnesota into
western Wisconsin this morning...with showers and a few
thunderstorms occurring along it. Winds will be switching to the
west-northwest behind the front.
Ceilings have varied from IFR to VFR across the Northland and that
will continue this morning. Areas of steady rain and far northern
Minnesota will be most likely to see MVFR/IFR ceilings...but they
should rise through the day. We expect cumulus development today and
ceilings from 3500-5000ft will be possible this afternoon. The cumulus
should dissipate late today into early evening. However...another
shortwave will move quickly through the area this evening into
tonight...and bring a period of low VFR ceilings and possible a
few showers to most taf sites.
Preliminary point temps/pops...
dlh 74 53 74 55 / 30 20 30 10
inl 69 47 73 53 / 10 20 30 30
brd 73 52 76 56 / 20 20 20 10
hyr 74 51 75 54 / 80 20 20 10
asx 74 53 76 56 / 80 20 20 10