Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 161747

Area Forecast Discussion
National Weather Service Marquette MI
147 PM EDT Fri Jun 16 2017

.SHORT TERM...(Today and tonight)
Issued at 509 AM EDT FRI JUN 16 2017

WV imagery and RAP analysis indicated a mid/upper level low over
nw Ontario with a mainly zonal pattern across the nrn CONUS. a
weak shrtwv supported isold light showers near Marquette and MNM.
Other weak shrtwvs were located upstream over ND and MN. At the
surface, a weak trouigh extended into nw MN from low pressure over
nw Ontario. Otherwise, mainly clear skies prevailed but abundant
low level moisture over the ern cwa has brought some patchy dense
fog to ESC/ISQ/ERY.

Today, Similar to yesterday, the combination of a weak shrtwv,
daytime heating and lake breeze boundaries will support sct
shra/tsra this afternoon. The greatest coverage is expected again
from near MQT to P53/Grand Marais and southward toward ESC. Since
dewpoints are mainly in the upper 50s to around 60 today,
compared to the mid and upper 60s yesterday over interior cntrl
locations, instability will not be as strong. Nevertheless, MLCAPE
values of 1000-1500 J/Kg are possible cntrl this afternoon
(compared to 2000-3000 J/Kg Thursday) which along with 0-6km shear
values in the 30-40 knot range could support some stronger storms
with gusty winds and small hail.

Tonight, a more signficant shortwave trough along with a broad 850-
700 mb WAA and 305k-310k isentropic lift will support increasing
rain chances over mainly the east half of Upper Michigan. There will
also be enough elevated instability for isold tsra.

.LONG TERM...(Saturday through Thursday)
Issued at 347 AM EDT FRI JUN 16 2017

Upper level troughing over Mantioba and northern Ontario into the
weekend will keep persistent chances for showers and possible
thunderstorms through the weekend. Greatest chances of showers and
thunderstorms occur Sat aftn into Sun morning as stronger
shortwave slides along in the base of the mean troughing from
northern Plains to the Upper Great Lakes. Small risk of severe
storms on Sat aftn and evening as shortwave arrives over western
Upper Michigan along with weaker sfc wave of low pressure. MLCape
up to 1500j/kg and deep layer shear over 40 kts seems sufficient
enough for organized storms especially over central and east
forecast area. Weakish mid level lapse rates less than 6C/km point
to pulsy type setup for the stronger thunderstorms. Light gradient
winds likely will lead to some lake breezes and that may provide
a focus for thunderstorms. Highs well into the 70s and lower 80s
away from lake moderation. Dwpts into the upr 50s to lower 60s
will result in a humid day.

As the shortwave moves through the area Sat night, sfc low and
associated cold front sharpen up while heading to eastern Upper
Michigan Sun morning. Steeper mid level lapse rates tied to the
shortwave trough and effective shear over 30 kts may lead to
stronger storms even in the overnight hours Sat night into Sun
morning as the sfc low moves through. Still could be some showers
around Sun aftn but limited sfc based Cape of mainly less than
500j/kg should keep potential for thunder low. Sfc low possibly
enhanced some by convection passing to the northeast of forecast
area on Sun will drag cooler air over Upper Michigan. Expect highs
in the 60s west and north behind the sfc low/cold front and maybe
reaching 70s scntrl before falling off in the aftn after the front
moves through. As the cold air arrives, expect breezy conditions
with gusts up to 25 mph to develop in the aftn. The gusty winds and
building waves on Lk Superior could result in elevated swim risk for
Alger county beaches of Lk Superior late Sun aftn into Sun evening.

Upper low over Manitoba and northern Ontario remains in place early
next week. Main sfc low will lift toward Hudson Bay. Result will be
some showers at times in weakly cyclonic low level flow. Stronger
shortwaves rotating around the upper low will lead to better chances
of rain especially if timing coincides with peak heating in the aftn.
Daytime highs will be blo normal both Mon and Tue with upper low in
the vcnty. Weak ridging aloft and sfc ridge should lead to dry day
on Wed with temps near seasonal norms, then another system moving in
to end the week should bring warmer temperatures along with chances
for showers and thunderstorms.

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 147 PM EDT FRI JUN 16 2017

Showers and thunderstorms have developed this afternoon as a weak
surface trough moved into the area. These showers and thunderstorms
are expected to mainly impact KSAW this afternoon, with only
mentions of VCTS as KIWD to hing towards the potential. Further
north at KCMX confidence is not as high in thunderstorm activity
this afternoon as the line of storms have developed to the east of
the terminal. Tonight, better chances for widespread showers and
perhaps a few rumbles of thunder will increase mainly after dark at
all terminals. So have included mentions of rain showers with some
VCTS at most terminals.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 509 AM EDT FRI JUN 16 2017

The pressure gradient will remain weak today with winds remaining 20
knots or less. Winds will increase again this weekend as a low
pressure system develops over the Upper Peninsula and Lake Superior.
This will give wind gusts into the 20 to 25 knot range by Sunday.
The wind direction will depend on the final track and placement of
the low.

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


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