Scientific Forecaster Discussion
fxus63 kmqt 261127
Area forecast discussion
National Weather Service Marquette Michigan
727 am EDT Mon Jun 26 2017
Short term...(today and tonight)
issued at 454 am EDT Monday Jun 26 2017
A shortwave over the upper Great Lakes and associated mid-level
q-vector convergence and deep moisture is supporting an area of
moderate to heavy showers over Schoolcraft and eastern Alger
counties early this morning. Some lighter showers are noted on
radar over the rest of the cwa, except far south central upper mi.
Moisture wrapping around this shortwave will continue to support
light to moderate showers which will pivot across mainly the
northern tier of the cwa early this morning before shifting across
the se half of upper mi late this morning into early afternoon with
the movement of the shortwave. Showers will taper off over the west
half of the cwa late this morning into early afternoon but could
linger into mid to late afternoon over the east before tapering off.
High temps will range from the upper 50s east under more persistent
showers and clouds to the lower to mid 60s west where clearing skies
are expected this afternoon.
As the mid-level trough/shortwave continues to push E of the region
this evening expect clearing skies to finally reach into the eastern
counties tonight, leading to cooler min temps. Look for min temps
from the lower to mid 40s over the interior to the upper 40s to
lower 50s near the Great Lakes shorelines.
Long term...(tuesday through sunday)
issued at 405 am EDT Monday Jun 26 2017
The main forecast highlights will be the brief arrival of near-
normal temperatures with a mostly dry day on Tuesday, but then
towards the middle of the week through the weekend, chance for rain
return as multiple systems are expected to track across the area.
The heaviest rain is expected to fall on Wednesday through Thursday
morning. With much of Upper Michigan seeing above normal rainfall
over the last week or two, heavy rain may bring flooding concerns.
Tuesday, expect much of the area to remain dry as high pressure
drops south from the northern plains into the Ohio River valley.
With ample diurnal heating expected through the day, expect lake
breezes to develop off of Lake Superior and the northern end of Lake
Michigan. Converging lake breezes across eastern portions of the
Upper Michigan may provide enough lift for a few isolated afternoon
showers, and perhaps a thunderstorm or two. Otherwise, expect much
of Upper Michigan to remain dry, with diurnal cumulus developing
downwind of lake breezes.
Tuesday night into Wednesday, surface low pressure will eject out of
the northern rockies and track across the northern plains as
shortwave energy traverses north central portions of the Continental U.S.. the
combination of low pressure to our west and the above mentioned area
of high pressure slowly tracking towards the mid-Atlantic states
should allow moisture-rich air from the Gulf of Mexico to funnel
northeast towards the upper Great Lakes region. This increase in
moisture will allow pwats to climb to around 1.5+ inches and
increasing warm air advection across the area will allow the warm
cloud depth to increase, setting the stage for efficient, heavy
rain. The medium range models have diverged a bit on the track and
speed of the system across the area, but they remain consistent with
Upper Michigan riding along the nose of the best moisture transport,
which should allow fairly widespread precipitation to start from
west to east through the day on Wednesday. Instability looks very
limited, but cannot rule out a few rumbles of thunder especially
closer to the Wisconsin/Michigan border. Wednesday night into
Thursday, as anomalously strong 850mb flow becomes enhanced, with a
50 knot low-level jet ramping up across Wisconsin, expect the focus
for heavy rain to shift east into Thursday. It is difficult to
pinpoint what areas will see the highest rainfall totals Wednesday
through Thursday, but given the antecedent wet conditions across
much of Upper Michigan, areas that see heavy rains may see Hydro
concerns increase. Even though the system will be exiting the area
on Thursday, lingering upper-level vorticity and wrap-around
moisture may still allow for lingering rain showers through the day.
Friday through the weekend, the upper-level pattern across the
medium range models begins to diverge, but with multiple shortwaves
expected to track across the area periods of showers will be
Aviation...(for the 12z tafs through 12z Tuesday morning)
issued at 720 am EDT Monday Jun 26 2017
IFR/MVFR conditions in showers/stratus at the taf sites this
morning will improve to VFR this afternoon as the low pressure
trough shifts east and drier high pressure builds in from the
west. High pressure will maintain VFR conditions under mostly
clear skies tonight.
Marine...(for the 4 am Lake Superior forecast issuance)
issued at 454 am EDT Monday Jun 26 2017
Winds of 10 to 15 knots are expected to continue through the first
half of next week as the pressure gradient decreases and high
pressure builds in for the first part of the work week. Towards the
middle of the week, winds will start to increase to around 20 to 25
knots as a system lifts across the upper Great Lakes. Winds will
then decrease to around or less than 15 knots towards the end of the
week and next weekend as the pressure gradient relaxes again.