Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Duluth Minnesota
1051 am CDT Tuesday Sep 30 2014
issued at 1046 amcdt Tuesday Sep 30 2014
Updated to keep clouds in the area a bit longer. Visible satellite
showing strong clearing in the tip of the Minnesota arrowhead and showing
breaks in the cloud cover elsewhere.. with strong subsidence
believe most areas will at elast go broken-scattered by early afternoon.
Looking upstream...strong warm air advection will bring clouds
back into the area tonight.
Short term...(today through wednesday)
issued at 309 am CDT Tuesday Sep 30 2014
Surface high pressure was building into the forecast area from northwest Ontario at 07z.
With the easterly flow over Lake Superior...this has resulted in
widespread cloud cover over the forecast area. However...latest infrared satellite
imagery reveals the back edge of the clouds heading for the tip of
The Arrowhead after just clearing Isle Royale. If this trend
continues...will have to adjust cloud cover this morning and
introduce a clearing trend. Otherwise...a quiet weather day with
cool maximum temperatures along the North Shore in the upper 40s. 50s to near
A deepening area of low pressure moves northward through the Dakotas
tonight...reaching southern Manitoba by 12z Wednesday. Models are
fairly similar in the mass fields but differences show up in the
quantitative precipitation forecast. The GFS is most generous...while the other models are less so.
Leaned away from the GFS quantitative precipitation forecast and sided with the other models. This
resulted in a new alignment of the probability of precipitation. Added back a mention of
isolated thunder tonight as a narrow corridor of 850 mb lifted indice's to -1c will
be found in the warm air advection zone in concert with the low level jet moving through the
On Wednesday...the low level jet moves over northwest WI as the surface low continues
northward. Upper divergence is maximized over the same are by 18z
Wednesday as right entrance region of h25 jet moves overhead. Left
out the mention of thunder in the morning as instability axis is
well S of the area. Added the isolated thunder mention back in the
afternoon as instability increases. Maximum temperatures will be a bit warmer
thanks to the warm air advection.
Long term...(wednesday night through monday)
issued at 309 am CDT Tuesday Sep 30 2014
An upper trough will extend from the central Canadian provinces
south through the northern plains into the southwest Continental U.S. Early in
the period. The trough will move east with a closed upper low
forming Thursday night over/near Minnesota/the eastern Dakotas. The
low will deepen over the western Great Lakes into the first part of
the weekend...then continue east/northeast into early next week with
a cold northwest flow aloft occurring over the region behind the
front. There will be chances for rain throughout much of the
A shortwave Wednesday night will bring a chance for showers to
mainly eastern areas...with the best chance occurring in the
evening. A stronger wave will develop a surface wave Thursday and
there will be a better chance for rain with these features. We
increased probability of precipitation quite a bit Thursday/Thursday night over much of the
County Warning Area. Chances still look to be highest over the eastern half of the
A cold upper low will be over the Northland Friday and the chance
for showers will continue. The upper low will only move slowly east
Friday night and showers will continue to be possible over mainly
the eastern half of the Northland. Colder temperatures will continue to
move in on northwest flow. It does look cold enough for some snow to
mix in over portions of the Northland Friday night. Little
accumulation is expected.
Most areas will see a break from the showers on Saturday as brief
ridging moves in. However...a chance for more showers returns
Sunday/Monday as a clipper moves through the area.
High temperatures will be in the sixties for most areas
Thursday...then drop into the upper forties to lower fifties for
Friday and Saturday. Highs Sunday/Monday will mainly be in the
Aviation...(for the 12z tafs through 12z Wednesday morning)
issued at 642 am CDT Tuesday Sep 30 2014
IFR/low MVFR ceilings covered the Northland this morning. These
clouds have expanded overnight across the region. Confidence
remains lower than average on how much clearing will occur today.
The inversion is rather strong and we are entering the time of
year where it takes longer for these type of clouds to
lift/dissipate. Most of the model guidance suggests the clouds
will lift and decrease. Bufr soundings show the ceilings lifting
and the moisture becoming very thin. We went with a more
pessimistic approach with the strong inversion either delaying or
keeping the clouds in tact through the period. We did go scattered
this afternoon at khyr/kbrd/kinl but only have a tempo group for
scattered lower clouds at khib/kdlh.
An area of low pressure will track north into Manitoba tonight and
some showers or a thunderstorm will occur over the region. Showers
will be possible at most taf sites later tonight and we have a
mention in most taf sits.
Preliminary point temps/pops...
dlh 51 46 56 51 / 0 50 50 40
inl 59 45 60 49 / 0 30 30 20
brd 59 51 65 50 / 0 40 20 10
hyr 60 47 57 53 / 0 50 70 40
asx 55 44 58 54 / 0 20 70 40
Minnesota...beach hazards statement until 8 PM CDT this evening for mnz037.
WI...beach hazards statement until 8 PM CDT this evening for wiz001.
Ls...Small Craft Advisory until 4 am CDT Wednesday for lsz142>147.