Area Forecast Discussion
Issued by NWS Duluth, MN
FXUS63 KDLH 220820
Area Forecast Discussion
National Weather Service Duluth MN
320 AM CDT Sat Apr 22 2017
.SHORT TERM...(Today through Sunday)
Issued at 320 AM CDT Sat Apr 22 2017
The main forecast challenges for the short term include shower
and isolated thunderstorm chances north today and very dry
conditions south, with minimum relative humidity values from the
low 30s to the teens. A wintry mix is possible overnight and
Sunday morning, switching back to all rain by late morning.
High pressure remained in place over the southern forecast area
early this morning while a cool front stretched from a surface low
over northern Ontario, southwest through southern Manitoba.
Cirrus was drifting into far northern Minnesota, while central and
northeast Minnesota and northwest Wisconsin saw clear skies. The
surface ridge will gradually drift southeastward out of the area
today and tonight as the cool front and trough of low pressure
advance into the Northland. Cloud cover over north-central
Minnesota will thicken and spread southeast today yielding partly
to mostly cloudy skies and slightly cooler temperatures for the
Borderland, Iron Range, and the northern portions of the
Arrowhead. Farther south, mostly sunny skies are expected.
Efficient boundary layer mixing is forecast south of the cloud
shield with NAM and GFS BUFR forecast soundings indicating a mixed
layer from around 775 mb in the NAM and nearly 750 mb from the
GFS. With temperatures climbing into the middle 60s, relative
humidity values will become quite dry with some areas recording
minimum RH in the low 20% to teens. The only thing working against
the very dry conditions would be thicker cloud cover extending
farther south than currently forecast. Any reduction in solar
heating would result in higher RH values. Winds are not expected
to be particularly strong, generally from 5 to 10 knots with a few
gusts between 15 and 20 knots possible during the afternoon. Even
with the recent rains, the lack of botanical activity will leave
much of the moisture in the ground. Dormant grasses and plants
will support easy fire starts this afternoon into early evening.
As the front sags south into the Borderland this afternoon,
scattered showers will be possible. Many deterministic models
feature very weak instability, 100-200 J/kg MUCAPE, and have
included isolated thunder generally north of the Iron Range east
into the Boundary Waters this afternoon. With the very dry
boundary layer, there is a chance the precipitation will evaporate
before reaching the surface. Have limited POPs to the low end of
the "chance" category until evening.
A broad upper-level trough will sag into Minnesota tonight.
Northwesterly winds along the front will tighten the thermal
gradient along the boundary tonight. The combination of increasing
frontogenesis and falling heights will allow precipitation to
expand in coverage across most of the Northland overnight.
Temperatures will be cool enough for a wintry mix of rain and
snow. Snow accumulation of up to an inch is possible in the higher
elevation areas of far northeast Minnesota. Temperatures
overnight will dip to near 30 degrees in the north, but will hover
in the upper 30s south.
The front is expected to stall over Minnesota and northwest
Wisconsin on Sunday. Nearly steady heights and a weakening thermal
gradient aloft will ease forcing for ascent. The area of
precipitation is expected to become narrower north of the
boundary, or possibly taper off entirely during the day. Precip
type will change back to rain as temperatures warm and rates
decrease. With mostly cloudy skies, and a cooler airmass in place
for the northern two-thirds of the forecast area, temperatures
will trend much cooler for the second half of the weekend.
Easterly winds off Lake Superior will keep temperatures very cool
along the shore and inland. Areas from Brainerd to Hinckley to
Phillips and south could see partial clearing during the
afternoon, allowing temperatures to rebound into the middle to
upper 50s, while the remainder of the Northland finds temperatures
in the upper 30s to middle 40s.
.LONG TERM...(Sunday night through Friday)
Issued at 320 AM CDT Sat Apr 22 2017
The long term period will be wet and increasingly colder.
The upper air pattern through the period will feature a broad
trough across the much of the nation. A series of embedded short
waves will contribute to a march of surface lows that will be
passing through the region. These low pressure areas will bring
clouds, precipitation and east winds off of Lake Superior- all
ingredients to keep the Northland cool
Specifically for Sunday night and Monday low pressure area will
develop and push into the High Plains Sunday night while the cold
front that came through Sunday stalls over central MN and WI. The
front then retreats north as a warm front as the low pushed warm
air into the region. Expect a mixed bag of precipitation along and
north of the front. Snow is mostly likely in far northern MN
while the precipitation types are more problematic farther south.
A few inches of snow could accumulate through Tuesday night by the
time the low pulls off to the east. In addition to the rain and
snow and other types of precipitation, there will be east winds
off of Lake Superior. So the winds and precipitation will make for
a very cool day Monday north of the front in mainly northeast MN.
Most of northwest WI will be south of the front and will be dry
and much warmer, in the 60s. There will be brief high pressure
Tuesday before another in a series of lows makes a beeline for the
Northland. The warmth will come to an end for all areas by
Wednesday as much colder air is pulled into the region behind the
retreating low. The next low has a few different scenarios played
out by the models with the GFS much farther north than the GFS. In
any case, colder and wetter weather will be coming in with this
low. And another high pressure builds in for Thursday and Friday,
possibly followed another low on Saturday.
.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1220 PM CDT Fri Apr 21 2017
High pressure will build over the region tonight and slowly drift
southward on Saturday. Late Saturday afternoon and Saturday
evening a cold front will slide into northern Minnesota. This will
result in VFR conditions at all terminals through much of the
forecast. Due to the approaching cold front, the pressure gradient
will tighten. This will result in gusty winds late in the morning
through the afternoon at KDLH/KHIB/KINL per the NAM/DLHWRF and
GFS. Rain will gradually spread into KINL and potentially KHIB
late Saturday afternoon and evening. Cannot rule out a
thunderstorm or two as there will be some instability in place,
however held off from including at KINL/KHIB as the potential is
low. As the lower levels moisten, expect MVFR ceilings to develop
at KINL around 00Z until the end of the forecast.
.PRELIMINARY POINT TEMPS/POPS...
DLH 63 35 41 31 / 0 50 30 30
INL 60 30 45 30 / 20 40 20 50
BRD 65 39 54 38 / 0 20 20 10
HYR 64 37 52 37 / 0 10 20 10
ASX 67 35 43 33 / 0 40 30 30