Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 181737

Area Forecast Discussion
National Weather Service Marquette MI
137 PM EDT Fri May 18 2018

.SHORT TERM...(Today and tonight)
Issued at 508 AM EDT FRI MAY 18 2018


High pressure over Quebec still driving the conditions across Upper
Michigan today. Low pressure trough resulting in showers and t-
storms over the central Plains will push a warm front north of Upper
Michigan today, so expect temperatures to warm considerably compared
to the cooler conditions observed on Thu. Highs over far western
Upper Michigan may reach 80 degrees while readings elsewhere will
reach the mid 60s to mid 70s, warmest over west half. The dry
airmass tied to the Canadian high will lead to RH values as low as
17-22 pct inland. If winds were stronger would need a Red Flag
Warning today, but there is some uncertainty on how much mixing will
occur due to persistent mid-high clouds over the area. Latest RAP
and HRRR indicate could see scattered to broken clouds lingering
even into mid aftn over parts of Upper Michigan. Since the pressure
gradient is not all that strong, mixing will dictate how strong
winds/gusts end up. Went with Special Weather Statement for all of
Upper Michigan due to the elevated wildfire potential. Dayshift can
upgrade to Red Flag Warning if needed, but just didn`t have the
confidence in seeing those stronger winds to go with one right from
the jump this morning.

Sensible weather stays quiet tonight as high pressure moves across
New England and front approaches western Lk Superior. Another system
will be lifting northward across the Ohio Valley as well. Rain
chances with both systems should stay out of Upper Michigan tonight
but will see clouds increase from the west and the south. Southerly
winds ahead of the front will keep temps in the 40s with even some
lower 50s possible far west and along Lk Superior from Keweenaw to
Big Bay and Marquette.

.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 18Z TAFS through 18Z Saturday afternoon)
Issued at 136 PM EDT FRI MAY 18 2018

VFR conditions with scattered mid and high level clouds will prevail
at all TAF sites through tonight. Gusty south to southeast winds
this afternoon, strongestt SAW will become lighter tonight, but more
LLWS will return to CMX as a southerly low level jet develops above
the low level inversion out ahead of an approaching front. MVFR cigs
are expected to move into western Upper Michigan at KIWD and to near
KCMX by late Saturday morning as a cold front moves through the area.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 508 AM EDT FRI MAY 18 2018

East to southeast winds of 15 to 25 kts will increase to 20 to 30
kts today over much of Lk Superior. Southeast winds will stay up
over eastern Lk Superior tonight, before diminishing late. Winds
will be less than 20 kts to start day on Sat but will shift north 20
to 30 kts in the aftn behind a front dropping across Lk Superior.
Winds will diminish to less than 20 kts late Sat night through the
rest of the forecast period as high pressure parks itself over the
Upper Great Lakes.

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


LONG TERM...Rolfson
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