Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 180836

Area Forecast Discussion
National Weather Service Marquette MI
436 AM EDT Fri May 18 2018

.SHORT TERM...(This evening through Friday)
Issued at 331 PM EDT THU MAY 17 2018

Light cloud cover continues to stream over Upper Michigan thanks for
convection across the northern Mississippi River Valley.  Dew points
have fallen quite a bit over the past 24 hours keeping RH
percentages down to the 20-30% range. In fact, dew points are
several degrees lower than expected this afternoon but so are high
temperatures owing to the aforementioned cloud cover.

Tomorrow is looking like a different story... This evening, winds
will start to veer easterly reaching southeasterly by Friday
morning. As dry air continues to filter into the region from Ontario
overnight, RH recovery will be be significantly limited with RH
percentages returning to only 50-60% by sunrise Friday. As the day
progresses, south/southeasterly winds will increase with gusts to 15-
20 kts (potentially 20-25 kts across the east) owing to a
strengthening pressure gradient from a high in eastern Canada and
low in the Southern Plains. Even with southerly winds transporting
higher-moisture air into the region, mechanical mixing will keep
dew points from significantly increasing across the area leading
to RHs staying in the 20-30% range Friday afternoon. I have some
concern that the dew points (and associated RH percentages) in the
current forecast are a bit too high given just how fast dew
points have fallen today... With that said it is not out of
question that RHs fall into the teens tomorrow afternoon.
Regardless, Friday is shaping up to be a dangerous fire weather
day with burning strongly discouraged.

.LONG TERM...(Saturday through Thursday)
Issued at 436 AM EDT FRI MAY 18 2018

Over the next 7-10 days, pattern will feature mean troffing over
eastern Canada downstream of mean ridging over western Canada. To
the s, shortwaves will occasionally progress across the CONUS in a
weak southern stream. Since the big late season snowstorm in mid
Apr, it`s been dry for the last 30 days, especially so over the w
half of Upper MI. W of roughly a Munising to Manistique line, pcpn
over the last 30 days has been less than 50pct of normal with fairly
large coverage of less than 25 pct of normal. The upcoming pattern
will favor continuation of the dry weather as the ridge/trof pattern
over Canada will work to force the more important pcpn producing
southern stream shortwaves mostly s of Upper MI while the more
dynamic northern stream shortwaves pass well to the ne. There will
be some opportunities for rainfall, but none look important to put a
notable dent in growing pcpn deficits. So, fire wx will be a
frequent concern over the next 7-10 days. As for temps, temps over
the next 7 days will fluctuate around normal as shortwaves dropping
into and reinforcing the mean eastern Canada trof will send cold
fronts occasionally s thru the Upper Lakes, bringing periods of
cooler weather, especially so close to Lake Superior where cooling
will be significantly amplified by the chilly lake waters. Overall
though, for most locations, more days will likely be above normal
than blo normal.

Beginning Sat, a northern stream shortwave will be swinging into
northern Ontario while a weak southern stream wave moves across the
Ohio Valley/southern Great Lakes. None of the models show
pcpn/moisture associated with the southern shortwave linking up with
the cold front associated with the northern wave. As a result, pcpn
will be lacking for Upper MI. Some shra may skirt the se fcst area
during the morning, but that looks doubtful. Meanwhile, cold front
associated with northern shortwave will move across the fcst area
during the day Sat. Weak forcing and lack of deep moisture suggests
nothing more than schc/low chc pops in the aftn/evening. Shra, if
they occur, will likely follow fropa. Little or no instability
precludes mention of any thunder. Winds will become light ahead of
the front, and with higher RH, fire wx concerns will ease on Sat.
However, will need to watch post frontal winds which will increase
and become gusty. While this will coincide with more clouds/slowly
falling temps/rising RH, it could be a concern if any fires start.

Another very dry air mass will settle over the area on Sun. Lowered
dwpts to the low side of avbl guidance given the potential of mixing
down drier air during the aftn. In the interior, expect highs up
around 70F with RH falling to around 20 pct. Fortunately, winds will
be light on Sun to prevent enhancement of fire wx concerns.

Mon into Tue...the CMC and especially GFS bring a southern stream
shortwave farther n than the ECMWF, resulting in shra for much of
the fcst area. Given the recent prevalence of eastern Canada
troffing which would force southern stream energy to the s, will
lean fcst toward the dry ECMWF scenario. That said, the 00Z ECMWF
trended farther n and is faster progressing the wave, resulting in
shra late Sun night/Mon. Until better agreement/run-to-run
consistency sets in, will continue to favor a drier fcst.

Dry weather will prevail Wed thru Fri. Looks like a northern stream
shortwave dropping into the eastern Canada trof will send a dry cold
front across the area on Wed. Max temps Wed could be quite a bit
lower than reflected in this fcst, especially closer to Lake
Superior, depending on timing of front and strength of the sfc high
following front.

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 141 AM EDT FRI MAY 18 2018

VFR conditions with scattered mid and high level clouds will prevail
at all TAF sites through the forecast period. LLWS will prevail at
all TAF sites through daybreak this morning. Southeast to east winds
will then gust over 15 kts at all the TAF sites later this morning
into the aftn. Strongest winds are expected at SAW. Winds become
lighter tonight, but more LLWS could return to CMX as a southerly
low level jet develops above the low level inversion.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 331 PM EDT THU MAY 17 2018

Northeasterly winds of 20-30 knots across the west will abate this
evening.  Winds will then veer south/southeasterly Friday and
increase to 20 to 30 knots across the east, especially Friday
evening. Winds will then decrease below 20 knots for the remainder
of the forecast period as a high pressure system parks itself over
the Upper Great Lakes.

Upper Michigan...
Lake Superior...
Lake Michigan...


SHORT TERM...Borchardt
LONG TERM...Rolfson
MARINE...Borchardt is the U.S. government's official web portal to all federal, state and local government web resources and services.