Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service Marquette Michigan
239 PM EDT Sat Sep 23 2017
Short term...(this evening through sunday)
issued at 239 PM EDT Sat Sep 23 2017
Upper air pattern consists of a 500 mb over the ern U.S. With a deep
500 mb trough over the western U.S. And rockies. It is a tale of two
seasons with Summer in the east and fall and winter in the western
U.S. For temperatures. The ridge remains over the upper Great Lakes
this forecast period with the area being in a warm and humid airmass
while the trough remains over The Rockies through 00z Mon. The
moisture and dynamics remain to the west and north of the area this
forecast period. Kept in some slight chance pops for this evening
across the far west and far north as about half the models have some
type of convection forming late this afternoon into this evening and
the other half are dry. Only went slight chance pops though.
Otherwise kept with persistence. Still looks very warm for Sunday
with southwest downslope flow helping to break a few records across
Long term...(sunday through friday)
issued at 458 am EDT Sat Sep 23 2017
Models suggest that a slowly progressive amplified pattern will
prevail with a prominent mid/upper level ridge over the Great Lakes
this weekend giving way to troughing by the middle of next week.
Much above normal temps and dewpoints are expected into Monday with
record highs and record high mins likely for many locations.
Sunday, even with a strong subsidence inversion near the 590 dm
ridge over the cntrl/ern Great Lakes, forecast mixing through 850 mb
temps around 17c will support readings in the mid 80s over much of
the area except downwind of Lake Michigan. Adding to the discomfort
will be dewpoints lingering into the mid and upper 60s. Low temps
should also remain in the upper 60s with some downslope locations
around 70. Subsidence/capping will be strong to suppress
shra/tsra chances, keeping the pcpn to the north and west.
However, the frontal zone over NE Minnesota into wrn Lake Superior may
allow some shra/tsra into the far west near iwd late Sunday night.
Mon-Tue, shra/tsra chances should increase by late Monday into
Monday night over the west half as the mid level trough advances
into the plains and the front approaches. The best chance for rain
is expected Tuesday as a stronger shrtwv and associated low lifts NE
near Lake Superior and drags the front through the area. The European model (ecmwf)
remained slightly faster/stronger with the mid level trough and
front and low compared to the GFS/gefs. Although temps will remain
above normal, greater cloud cover will keep Max readings around 80
Monday and the lower 60s to lower 70s Tuesday.
Wed-Fri, cooler/drier air should finally take over with breezy WNW
winds behind the front. 850 mb temps dropping to around 3c Wed into
Thu along with wrap-around moisture will bring potential for some
sct light showers. Models have trended toward a stronger shortwave
moving in by the end of the week with even colder air (850 mb temps
to around -4c) which would bring increasing rain and lake enhanced
rain chances with brisk northerly winds. Highs during the period
will be mainly in the 50s.
Aviation...(for the 18z tafs through 18z Sunday afternoon)
issued at 1235 PM EDT Sat Sep 23 2017
VFR conditions are expected at all taf sites through most of the
period. There will be some brief periods of MVFR fog at all sites
Marine...(for the 4 PM Lake Superior forecast issuance)
issued at 239 PM EDT Sat Sep 23 2017
Low to mid 60s dewpoints sliding across Lake Superior are expected
to linger into Tue bringing patchy to areas of fog across the lake.
Some of the fog could be locally dense at times. Expect winds to
generally be below 20 knots through the early part of next week
under a weak pressure gradient. As a cold front moves across Lake
Superior Tue night into Wed with colder air coming in, winds will
increase to 20 to 30 knots for gusts and these would be the strongest
winds for this forecast period.