Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Duluth Minnesota
947 PM CDT Sat Mar 15 2014
issued at 947 PM CDT Sat Mar 15 2014
Arctic high pressure just north of the Canadian border will settle
southeastward across the Northland overnight..bringing a return to
rather frigid temperatures in many areas. With clear skies/light
winds/very cold airmass and lingering deep snow cover..temps have
nose-dived very rapidly this evening with Crane Lake already at
-8f and Grand Marais at -2f as of 930 PM. Many other locations
have fallen close to 20 degrees already since Sundown. Overall
temperature forecast was in decent shape..but we have made a few downward
adjustments..most notably to some of the favored areas such as Crane
Lake and the tower/Embarrass areas..where readings will likely
push at least -25f at some point overnight.
Cold temperatures and recently opened water have also resulted in some
light lake effect snow showers affecting the western side of the Bayfield
peninsula the past hour or so..but with flow continuing to
diminish in the low levels..drainage winds should prevail by
midnight-1 am..which should act to keep snow showers out over the
Return flow on the south side of the ridge will rapidly commence
Sunday morning with a rapid increase in clouds as low-middle level warm
advection intensifies during the day. This should be sufficient
for light snow moving into the northwest County Warning Area by middle-late afternoon Sunday.
Short term...(this evening through Sunday afternoon)
issued at 249 PM CDT Sat Mar 15 2014
Main concerns in the short term remain focused around the low
potential for light lake effect snow showers late this afternoon
and early evening along the South Shore and around the head of the
lake...and also the very cold temperatures expected tonight over
much of the Northland. Otherwise very quiet conditions in the
A large area of high pressure at the surface is building in across the
upper Midwest this afternoon and will be the dominant force tonight
and much of tomorrow with mostly clear skies...light winds and cold
temperatures. Flow aloft will remain active from the northwest through the
rest of the weekend as cold Arctic air spills into the Great Lakes.
This cold air is trying to enhance the temperature profiles over the lake
and develop an area of lake effect clouds and snow showers over
sections of western ls this afternoon. The advection of dry air from
the northwest and the exiting cold air mass to the east...along with weak
bl wind shear are all contributing negatively to the formation of
lake effect clouds/snow. So...have downplayed the mention of snow
along the South Shore and around the western tip of the lake late this
afternoon and early evening. Although cannot rule out an outside
chance of a few flakes falling out of a bank of low clouds along
the shore. The air mass moving in will also be very dry and allow
skies to remain clear through tonight and much of Sunday. The
presence of the surface high will produce light/calm winds over much
of the region tonight...and when combined with clear skies and a
fleeting cold air mass will produce surface temperatures into the
single digits and teens below zero. A few locations reaching -20
is not out of the question especially for inland low lying areas
of The Arrowhead and northwest WI.
The high pressure will move to the east quickly tomorrow with a
return southerly flow developing over the Dakotas and Minnesota in the afternoon.
Modest warm air advection in the middle-levels will develop Sun afternoon ahead of the
next short wave coming in from the northwest. These two features will allow cloud
cover to increase during the day...but with conditions remaining
dry. Temperatures will warm quickly Sun morning into the teens and
lower 20s...with locations to the west reaching into the middle 20s by
Long term...(sunday night through saturday)
issued at 249 PM CDT Sat Mar 15 2014
Focus on snowfall amounts Sunday night/Monday...as well as potential
for well organized low pressure system to affect the region
As the surface/850 mb ridge exits to the east Sunday night...winds will
increase out of the south as a warm front pushes across the
forecast area. The strong warm air advection will trigger widespread light snow
Sunday night into Monday morning. There is a small threat for the
snow to mixed with sleet or light freezing rain in the SW zones/Brainerd
region. Most locations can expect light snow accums around an inch.
The exception will be along the North Shore of Lake Superior where
onshore winds will promote lake enhanced moisture and higher
snowfall amounts. At this time...generally 2-4 inches is anticipated
along the North Shore late Sunday night through Monday afternoon.
A negative tilted trough will make landfall in the Pacific northwest Sunday
night...deepening into a closed 850 mb low as it translates east across
The Rockies and into the northern plains Monday/Tuesday. The low will
lift the warm front/inverted trough into the Iron
Range/Borderland region Monday night. Models are continuing to
struggle with the placement of this boundary...which will become the
focus for a corridor of heavy snow Tuesday.
Although the track differs and will have a significant influence on
ptype/snow amounts...latest model runs are in reasonable agreement
that the surface low pushes out of South Dakota Tuesday morning. The low then
tracks east across southern Minnesota/northern Iowa through Tuesday
afternoon...reaching Lake Michigan Wednesday. This storm track will favor
easterly boundary layer winds over Lake Superior...and may help to
enhance snowfall amounts for locations along the shores of the Great
Lake. The main period of moderate to heavy snow accumulations for
portions of the Northland will arrive Tuesday...ending from west to
east through the day Wednesday. Lake effect snow showers will likely
linger along the South Shore/northern wisc zones into Thursday morning.
Will hold off on issuing a watch at the moment. However...have ramped up
probability of precipitation/snow amounts for Tuesday/Wednesday into the categorical range.
Have also included stronger wording with higher confidence in the
afternoon severe weather potential statement update.
Aviation...(for the 00z tafs through 00z Sunday evening)
issued at 655 PM CDT Sat Mar 15 2014
Fairly straightforward aviation forecast for this taf period.
Arctic ridge axis will settle southward over NE Minnesota/northwest WI
overnight..resulting in winds becoming light/variable by 02z.
Lingering boundary layer clouds should also rapidly dissipate
during the first couple hours of the taf period. We may see a
redevelopment of lake effect clouds tonight with rapid/significant
boundary layer cooling..but with light low level flow..drainage
flow from land to lake should act to keep any clouds that reform
mostly over the water..and would likely only affect kdlh.
S/SW surface winds should rapidly develop in the 8-16 knots range by
14-17z Sunday as pressure gradient rapidly tightens in
strengthening warm advection pattern. Clouds will also rapidly
thicken during the last 6 hours of the period..with light snow
beginning to affect kinl toward 00z Monday. Light snow also
expected to affect khib/kdlh just after the end of this valid taf
Preliminary point temps/pops...
dlh -6 20 15 30 / 10 10 50 50
inl -13 23 15 32 / 0 30 60 40
brd -4 24 18 35 / 0 10 40 30
hyr -12 20 11 29 / 0 10 20 40
asx -7 21 11 31 / 10 10 20 50