Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Marquette Michigan
754 PM EDT Wednesday Apr 1 2015
Short term...(this evening through thursday)
issued at 402 PM EDT Wednesday Apr 1 2015
Middle to high warm air advection clouds and light showers linger from North Lake Superior
through the east third of the County Warning Area at 20z this afternoon. The main focus
is turning to the west where we have ongoing convection being helped
out by the Lake Superior lake breeze. Expect this area that has been
producing pea sized hail to diminish in intensity as it exits the
lake breeze area and moves closer to Upper Michigan.
Kept the potential for isolated thunderstorms along the WI border
through the overnight hours...closer to the ribbon of instability
over WI. With strong warm air advection and a 40-50kt low level jet tonight...expect temperatures to
stay in the 40s for most locations. The favorable downslope areas
over the west half
the Keweenaw peninsula/ along Lake Superior may stay in the middle 40s.
Over the east a few pockets of upper 30s will not be out of the
question...farther away from the nearing surface low over east ND and far west
Minnesota...with a few more pockets of clearing possible.
Expect low relative humidity/strong gusty winds to develop Thursday
afternoon...with relative humidity values bottoming out 20-25 percent west of a line
from around Baraga to Iron Mountain. After coordinating with fire
user groups and due to The Pockets of snow still in the Woods...and
recent precipitation...a wildfire potential statement or Fire Weather Watch
is not needed at this time. Expect temperatures to rise near 60f over the west
half of the County Warning Area...while linger in the 50s west-west-southwest under increasing surface
winds. Expect middle to late afternoon gusts nearing 30mph over the far
west near iwd.
Long term...(thursday night through wednesday)
issued at 417 PM EDT Wednesday Apr 1 2015
Thursday night into Friday...shortwave and associated cold front push through
Upper Michigan Thursday evening. Cold air advection in the wake of the front will drop 850 mb
temperatures to -10c to -12c by 12z/Fri. With inversion heights dropping to
around 5k feet...and marginal instability for les...only lower end
chance probability of precipitation were included from late Thursday night through Friday morning
for northwest flow favored areas. Also with fairly extensive ice cover
lingering over much of Eastern Lake Superior this may further limit
any les over eastern counties. With much colder air moving in expect
fridays high temperatures in the lower to middle 30s...about 25 degrees lower
Friday night into Sat...precipitation chances will increase again late Friday night
into Saturday as models show another weak clipper shortwave moving
through the northern lakes. However...with only limited moisture
available in a northwest flow and fairly weak forcing indicated...any
snowfall amounts should amount from a dusting to half an inch. If
precipitation occurs south central it could briefly mix with rain due to
expected warmer temperatures there...but dryness of airmass and associated
evaporative cooling should tend to keep predominant precipitation type snow.
Sun...still plenty of model differences and thus lower forecast
confidence as the pattern transitions from northern branch dominant
to more zonal Pacific flow. The 00z/12z European model (ecmwf) runs allow another
stronger shortwave to bring a batch of snow into the area sun while the
GFS keeps dry conditions with middle-level and surface ridging over the
area. 12z Canadian run offers more of a compromise bringing precipitation
into mainly the far scntrl County Warning Area. For now will maintain going low slight
chance probability of precipitation until models come into better agreement.
Mon-Wed...as a trough digs into the western Continental U.S. The resulting SW flow
through the plains toward the Great Lakes and warm air advection pattern could
bring additional precipitation to the northern lakes. The 12z European model (ecmwf) still shows
confluent flow and drier conditions into the northern lakes on Monday
similar to 00z run...but begins to trend farther north with plains
system for Monday night into Tuesday night bringing precipitation into the area.
Meanwhile...the 12z GFS and Gem-New Hampshire bring plains surface low and associated
warm front farther north already on Monday spreading precipitation into SW and
scntrl portion of the County Warning Area. Given model uncertainty for now will
continue to utilize a model blend for probability of precipitation Monday into Tuesday night
keeping chance probability of precipitation across the area...highest to the south closer to
warm front. Wednesday looks drier as both European model (ecmwf) and GFS have high pressure
ridge building in from north of Lake Superior.
Aviation...(for the 00z tafs through 00z Thursday evening)
issued at 754 PM EDT Wednesday Apr 1 2015
Cold front will move across Upper Michigan late tonight/Thursday morning. Ahead
of the front...low-level jet will translate across the area...
leading to low level wind shear tonight at kcmx/ksaw where surface winds will be more
decoupled than at kiwd. Latest kmqt VAD wind profile (2338z) shows a
S wind of 40kt at 500ft above ground level. Scattered -shra are expected tonight...mainly
during the evening. Will watch thunderstorms and rain currently in northwest WI as they may
reach kiwd this evening if they hold together. While VFR conditions
should prevail tonight at all terminals...there is some potential of
MVFR ceilings just ahead of the cold front late tonight/early Thursday
morning at ksaw. Conditions will be VFR on Thursday as very dry air mass
sweeps into the area behind cold frontal passage. Winds will also become gusty
to 30kt or more Thursday afternoon at kcmx and especially at kiwd under very
Marine...(for the 4 PM Lake Superior forecast issuance)
issued at 402 PM EDT Wednesday Apr 1 2015
As a ridge of high pressure moves off the middle Atlantic coast
tonight...low pressure just west of International Falls will move east.
An associated trough/cold front will Cross Lake Superior late
tonight and Thursday morning while the low moves over North Ontario. South-southeast-
S gale force gusts of 35kts will be possible over mainly Central
Lake Superior into the early overnight hours. A secondary cold front
will then Cross Lake Superior Thursday evening as the low moves
across James Bay. High pressure will then move into the north Central
Plains on Friday...and the middle MS and Ohio River valleys on Saturday.
Look for a weak trough to cross the upper Great Lakes on Saturday.
For Sunday and Monday...a high will settle across Manitoba and
Ontario...as broad low pressure forms across the Central Plains.
Gale Warning until 10 PM EDT this evening for lsz244-245.
Gale Warning until 11 PM EDT this evening for lsz265.
Gale Warning until midnight EDT tonight for lsz264-266.