Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 191911
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
311 PM EDT Sat May 19 2018

.SHORT TERM...(Today and tonight)
Issued at 514 AM EDT SAT MAY 19 2018

A lot of moving parts to today`s forecast. Does appear that most
areas will see some showers due to two systems trying to converge
across the area. Could even see some bonus wetting rainfall in parts
of the east half of Upper Michigan, but given latest radar trends
not so sure on that. Given the dry stretch we have been in
essentially since the mid April storm over most of Upper Michigan,
fair to say that any rainfall will be welcome. Other impacts
today will be developing strong/gusty winds on Lk Superior and
eventually northern Lk Michigan

WV loop and mid-level heights show an overall west to east flow
pattern in place across the Conus. Flow is split though, with
southern stream shortwave H7-H5 trough over IL/IN while northern
branch shortwave axis is along Ontario/Manitoba border. Regional
radar shows no rain over Upper Michigan at present but that will
change shortly. Rain showers lifting across northern Lower MI and
northeast WI to the north of the southern stream shortwave are
pegged well by H7 moisture transport. This forcing is forecast to
steadily lift north into cntrl Upper Michigan so have widespread
light showers spreading into Menominee in the next hour or two, to
Escanaba and Manistique by 7 am and into the Marquette, Munising and
Newberry areas by 10 am. Based on radar trends, think the 0.5 inch
or more rainfall shown by RAP and HRRR in swath from Door Peninsula
to eastern Marquette county are likely way too aggressive, but some
light rain should occur. Otherwise, main issue here is how far west
will steady rain expand. Right now, looks like line will be vcnty of
Marquette to Hermansville in northern Menominee county. Expect this
initial batch of rain to exit eastern forecast area early aftn.
Could be some redevelopment of showers over north central late
morning into early aftn as northern branch shortwave trough catches
up with lingering deeper moisture from lead system. Main axis of
showers over northern MN with northern branch shortwave arrives over
Keweenaw by early aftn and then translates across rest of area into
early this evening while diminishing as stronger forcing aloft lifts
across northern Ontario.

Next issue is tied to affect of sfc cold front passage. Expect front
to move into far western Upper Michigan by mid morning and into
central Upper Michigan by mid aftn. Front will surge into scntrl and
eastern Upper Michigan by early evening. Northeast to north winds
will become gusty to 20-30 mph behind the front. Even stronger wind
gusts over 30 mph will be possible this aftn into this evening near
Lk Superior and also over central forecast area from Marquette and
Munising to Sawyer and Escanaba. Temps behind the front will quickly
fall into the 40s/50s. Temps ahead of the front were a real
challenge due to the initial system lifting in from the south.
Overall kept the idea that temps could reach low 70s inland west
(thanks a lot to a very warm start this morning as LNL is still 54F
as of 5 am) before the front comes through. Farther east though, did
lower temps significantly over much of the east half with the
expected clouds and rain this morning and then not much time to
recover before the front blasts through this aftn.

Weather will quiet down tonight with some clouds and gusty winds to
start the evening giving way to some clearing and diminishing winds
overnight as high pressure builds in from the west. Just a small
chance of showers early in the evening but otherwise should be dry
tonight. Lows will tumble into the 30s later tonight, coldest inland
west where temps may drop to freezing.

.LONG TERM...(Sunday night through Saturday)
Issued at 311 PM EDT SAT MAY 19 2018

Next week, high pressure will take hold across the region and favor
the return of above-normal temperatures, dry conditions, and fairly
light winds. Given the light winds expected and ample insolation,
expect lake breezes off of Superior and Michigan to dominate the low-
level wind fields during the day. These conditions will promote RHs
plummeting into the 20s away from the Great Lakes during the
afternoon hours, but thankfully RH recovery during the overnight
hours looks highly favorable. The lower RHs and unseasonably warm
temperatures will lead to the return of fire weather concerns,
especially on Monday when diurnal mixing could promote wind gusts
upwards of 12-15 mph across the interior. Moving towards the middle
of the week, thankfully winds are expected to remain light. A few
shortwaves are progged to track across the Great Lakes region, which
could lead to periodic chances for precipitation. However, there is
far too much uncertainty in the track of the shortwave and moisture
return this far north say if any of this precipitation will get into
Upper Michigan.

Friday through Memorial Day Weekend, a more active pattern will
begin to track across the region as a quick moving shortwave tracks
across the northern Plains and down across the Upper Great Lakes
Friday into Saturday. With moisture return progged to reach well
into the northern Rockies and Plains as the Gulf of Mexico will be
wide open for days prior, there could be enough instability that
gets this far north to promote chances for thunderstorms ahead of
the cold front Friday into Saturday. As to whether or not we will
see any strong to severe storms, we will have to see how the shear
profiles and instability gradients evolve ahead of the cold front
later this week. Behind the cold front, the tail end of the Memorial
Day weekend looks to be quieter and cooler. However, it`s important
to note that if the arrival of the above mentioned shortwave and
cold front are delayed, the chances for showers and thunderstorm
could arrive a bit later than currently forecast.
&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 130 PM EDT SAT MAY 19 2018

A sharp cold front moving through Upper Mi today will bring a
period of MVFR conditions to the TAF sites today. Expect isolated
to scattered rain showers along and behind the front. Greatest
chance for rain this afternoon will be at CMX as the front crosses
the area. North winds will also gust up to 20-25 kts behind the
front this aftn. Conditions should improve to VFR and winds should
begin to die down over the western TAF sites by early evening as
high pressure and drier air pushes in from the west. MVFR
conditions will continue into early evening at KSAW as will the
gusty north winds. By late tonight, expect decreasing clouds and
diminishing winds at KSAW. VFR conditions with lighter winds are
expected on Sun.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 514 AM EDT SAT MAY 19 2018

Southeast winds to 25 knots over mainly east Lk Superior will give
way to strong northeast to north winds through the aftn as strong
cold front crosses Lk Superior west to east. Could see gale gusts
over north central sections late morning into the aftn. As high
pressure quickly builds in late tonight expect winds to diminish blo
20 kts across all of Lk Superior by daybreak Sun. These light winds
of mostly 15 kts or less will continue through much of next week as
high pressure parks itself over the Upper Great Lakes.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...JLA
LONG TERM...Ritzman
AVIATION...Voss
MARINE...JLA



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