Area Forecast Discussion
Issued by NWS Duluth, MN
FXUS63 KDLH 251756 AAB
Area Forecast Discussion...UPDATED
National Weather Service Duluth MN
1256 PM CDT Tue Oct 25 2016
Issued at 1256 PM CDT Tue Oct 25 2016
Please see the new 18Z Aviation Discussion below.
.SHORT TERM...(Today through Wednesday)
Issued at 322 AM CDT Tue Oct 25 2016
A ridge of high pressure extended south from northern
Ontario/Manitoba through Wisconsin early this morning. Some mid to
upper level clouds have been moving through the region but there
have been plenty of clear periods leading to cold temperatures.
Temperatures at 08Z ranged from the middle twenties to lower
thirties for most areas with some pockets even colder. The surface
ridge will continue to move east today and a shortwave will cause
the upper ridge that extended from the Central Plains north into
Saskatchewan to flatten as it moves east this morning. Low
pressure to the lee of the Rockies will become more organized late
today into tonight with the center of the low moving into central
Iowa by 12Z Wednesday then into central to northern Illinois by
Increasing warm air and moisture advection today into tonight
will cause clouds to thicken with it becoming cloudy late today or
this evening for most areas. PWAT values will rise to 0.80 to 0.90
inches from the Brainerd Lakes into northern Wisconsin tonight
which is in the 90th percentile of climatology for this time of
year. We did delay the chance for rain until later this afternoon
in southern portions of the Northland then increase the chance
from south to north overnight. The best chance will continue to be
over the southern half of the Northland tonight into Wednesday. We
do have rain for the precipitation type for most areas through
Wednesday. However, soundings and max wet bulb temperatures in the
lowest couple thousand feet suggest a rain and snow mix may occur
in spots later tonight into Wednesday morning. This would be most
likely over the Arrowhead and over parts of northwest Wisconsin.
Near surface temperatures will be critical in determining
precipitation type and we expect them to be mainly 37F+ tonight
into Wednesday for most areas. The Arrowhead may not see much
precipitation at all from this system and we did trim back some
there. The coverage of precipitation will diminish Wednesday
afternoon as the low moves into Illinois and surface ridging
develops between the southern low and low pressure further
northwest over the Manitoba Lakes region.
As the surface pressure falls due to the low development further
west today, winds will increase out of the east to southeast and
be strongest around Lake Superior, especially at the head of the
lake. Temperatures today will be cooler and be in the lower
forties to near fifty. It will be cooler Wednesday with highs from
40 to 45.
.LONG TERM...(Wednesday night through Monday)
Issued at 322 AM CDT Tue Oct 25 2016
Progressive pattern continues across North American through the
weekend and into early next week with mild temperatures and
occasional chances for light precipitation, with the best chance
for widespread precip likely focused on our neighbors to the north
late- week. For such an "active" progressive weather pattern on
the synoptic scale, it`s fairly "quiet" locally.
On the synoptic scale one of the defining features for the
forecast period is a weak 850mb high centered across the southeast
U.S. which combined with a fairly persistent mid-level ridge over
the Rockies helps to maintain southerly flow across the Great
Plains and Mississippi River Valley through the period. This flow
brings milder air to the Upper Midwest, with the somewhat
persistent ridge over the Rockies helping to keep the storm track
along or north of the Canada-U.S. border and thus hold back the
colder airmasses which would otherwise typically make it into the
region this time of year.
Wednesday night into Thursday a low chance for light
precipitation across northeast Minnesota due to a weakening low
moving from central Manitoba into northwest Ontario. Late Thursday
a warm front lifts northeast across the northern Plains into the
upper Midwest resulting in increasing clouds, but a mid-level
longwave ridge building in from the west will result in enough
subsidence to preclude a chance for precip.
Friday into Saturday a shortwave trough ejects out of the Rockies
into the northern Plains/southern Canada resulting in a deepening
low centered over the upper Midwest Friday evening. With the warm
front to the north at this point the best chance for widespread
precip will be located to the north where the best combination of
warm air advection and PVA will be located, though cannot rule out
light precip along the international border, especially as a cold
front moves through associated with the low Saturday morning as it
moves to north of Superior and eventually towards southern
Ontario. Cooler air moves in aloft behind the low with a broad
area of high pressure across southern Canada and northern Plains
late Saturday moving over western Lake Superior Sunday morning.
Increasing southerly winds late Sunday into Monday as a series of
mid-level shortwaves eject out of Rockies and into Great Plains.
While guidance differs greatly in timing and track, eventually it
looks like a low pressure will organize around the Upper Midwest
early next week bringing a chance for precipitation on Halloween.
Temperatures mild through the period with highs in the low 40s to
mid 50s most days, lows in the 30s to mid 40s - most nights going
without reaching the freezing mark. While the normal lows for the
end of October are below freezing (by Oct 31st normal low at DLH
is 30, INL 26) these mild temperatures are far from breaking any
records at this point. For the month, assuming our forecast at
Duluth is perfect we would end the month with an avg temp
departure of +4.2F - about the 28th warmest on record in 143 years
of reliable records... mild, but hardly extreme.
.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1256 PM CDT Tue Oct 25 2016
VFR conditions continue into this evening, eventually lowering to
MVFR and possibly IFR late tonight and Wednesday. Developing low
pressure will move toward the Northland tonight bringing clouds
and rain showers into the area. Ceilings are expected to lower to
MVFR at BRD and HIB this evening and lowering at the remaining
terminals overnight. Light rain will spread eastward out of
western Minnesota and the Dakotas as the low pressure moves into
Iowa and the eastern Dakotas late tonight. The onset of the
rainfall is somewhat uncertain, with rain beginning at BRD this
evening and spreading east and north with time. Think INL will be
last to see the showers, if at all. With precipitation arriving
during the overnight, think we`ll see visibilities lower to MVFR
and possibly IFR. Best bet at lower visibilities will be at BRD
where, rain will fall for the longest duration. Ceilings at DLH
may lower into IFR range overnight with upslope flow off Lake
Superior. Confidence is too low to include in a prevailing group
at this time. Overall confidence in the forecast is above average
until 26.01Z, then average until 26.08Z, and below average
.PRELIMINARY POINT TEMPS/POPS...
DLH 47 38 42 38 / 10 50 80 30
INL 48 36 44 38 / 0 20 50 30
BRD 51 40 45 38 / 40 100 80 10
HYR 51 39 44 35 / 10 90 90 20
ASX 50 38 45 37 / 10 40 60 30
LS...Small Craft Advisory from 4 PM this afternoon to 10 PM CDT
Wednesday for LSZ143>145.
Small Craft Advisory from 4 PM this afternoon to 4 AM CDT
Thursday for LSZ141-142.
Small Craft Advisory from 11 PM this evening to 4 AM CDT
Thursday for LSZ140.