Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Marquette Michigan
348 am EDT Sat may 23 2015
Short term...(today and tonight)
issued at 347 am EDT Sat may 23 2015
Surface and upper ridging will become increasingly dominant through
tonight as a weak surface trough currently over the area moves east. A few
light rain showers have been observed along the trough mainly north of
Lake Superior early this morning. Showing potential will continue
along the front...with some isolated showers not out of the question
for Eastern Lake Superior and far northestern Upper Michigan mainly this morning.
Southwesterly flow and 850mb temperatures 7-10c warmer than yesterday will make
today warmer for sure. Looking at high temperatures in the 70s away from
Lake Michigan...with a couple 80 degree readings possible in the
warmer spots. Skies will be mostly sunny today until some upper
clouds move in from the SW late. Deep mixing and dry airmass
overhead will lead to min relative humidity values as low as 20 percent over the
interior west. West-SW winds will be strongest over the Keweenaw and near
Lake Michigan with winds gusting to 20-25mph...but cooler temperatures in
these areas will keep relative humidity values higher. Elsewhere...winds will
generally gust 15-20mph.
Clouds will continue to slowly expand in from the SW
tonight...keeping min temperatures warmer in the 40s to middle 50s...warmest
in downsloping areas from the SW winds.
Long term...(sunday through friday)
issued at 316 am EDT Sat may 23 2015
NAM shows the upper air pattern consists of a 500 mb shortwave ridge
over the upper Great Lakes 12z sun with a trough moving into the
northern plains Sun night. This trough then moves into the upper
Great Lakes Monday night. NAM brings in some 850-500 mb q-vector
convergence and deeper moisture Sun night into Monday before a dry slot
moves in Monday evening and wraparound moisture moves in Monday night
with some more q-vector convergence.
Did not make too many changes to the going forecast overall. Kept
Sunday morning dry and bring in some probability of precipitation late into the west and
south Sun afternoon and then bring likely probability of precipitation in for Monday. Did
not make too many changes to the temperatures either.
In the extended...GFS and European model (ecmwf) show a 500 mb over the upper Great
Lakes 12z Tuesday with a ridge on the East Coast. More troughing moves
into the upper Great Lakes 12z Wednesday. A surface front then remains over
the area through Friday...so unsettled weather will continue for this
forecast period with some probability of precipitation in there. Temperatures look to stay
above normal for this forecast period.
Aviation...(for the 06z tafs through 06z Saturday night)
issued at 137 am EDT Sat may 23 2015
With dry air mass lingering over the area through tonight...VFR
conditions will continue at kiwd/kcmx/ksaw through this forecast period. As
a disturbance passes across northern Ontario overnight/this morning...scattered
to perhaps broken middle clouds may brush the area. In addition...
nocturnal inversion and tightening pressure gradient will result in low level wind shear
at kcmx/ksaw overnight...and then a few hours after sunrise...winds
will become gusty at kcmx/ksaw. Gusts may exceed 25kt at kcmx for a
period this morning/early afternoon.
Marine...(for the 4 am Lake Superior forecast issuance)
issued at 347 am EDT Sat may 23 2015
Winds will continue to gusts to 25 kts over portions of Lake
Superior through today. Marine layer will restrict strongest winds
from reaching the surface as warm air slides over much colder waters
of Lake Superior. Winds diminish to less than 20 kts this evening
and should remain at or less than 20 kts through the middle of next
week as a weak pressure gradient persists.