Area Forecast Discussion
Issued by NWS Marquette, MI

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247
FXUS63 KMQT 250911
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
511 AM EDT Fri May 25 2018

.SHORT TERM...(Today and tonight)
Issued at 441 AM EDT FRI MAY 25 2018

Early this morning, as a subtle shortwave lifted across the region a
35 to 45 knot low-level jet ushered in additional low-level
moisture, providing additional lift and elevated instability for
convection tracking across Upper Michigan to work with. Upstream of
the region an elongated upper-level trough continued to slowly track
across the Northern Plains and into the Upper Mississippi Valley
with multiple shortwaves notable on water vapor imagery, including
the main shortwave moving across North Dakota. The main forecast
concern today is the chance for strong to severe thunderstorms this
afternoon and evening. Anyone with outdoor activities planned for
today through early tonight should keep a close eye on the weather.

We`re looking at another very warm and muggy day across much of
Upper Michigan today, with temperatures expected to climb into the
80s across the west half and 70s across the east half. Depending on
how cloud cover evolves through the late morning hours, we could see
a few locations approach the 90 degree mark this afternoon where
southwest flow would aid in downslope warming. Closer to Lake
Michigan, southwest flow off Lake Michigan should keep temperatures
in the upper 60s. With dewpoints this morning already in the low to
mid 60s, don`t expect moisture to be a concern for convection later
today. The combination of a humid airmass, diurnal heating, and
remnants of an elevated mixed layer steepening mid-level lapse rates
later today should allow for ample instability to setup across the
region. Shear on the other hand looks on the marginal side, with
deep layer shear approaching 25-30 knots at best. With a modest
cape, low shear setup today, expect storms to be pulsey. A few
storms may remain somewhat organized initially, but as cold pools
interact and the main shortwave moves across the area, expect
convection to congeal into a line as cells moves west to east across
the area. While wet-bulb freezing heights are around 10kft, thinking
the lack of shear should will limit the potential for large hail.
However, if we do see temperatures reach the mid to upper 80s across
the west half, the presence of inverted-v soundings and the
potential for collapsing updrafts should lead to the potential for
microbursts, and thus damaging winds. Along with damaging winds,
heavy rain will be a potential threat as storms will not be moving
fast and cell mergers may promote training of showers and
thunderstorms.

Right now, confidence is highest that convection will initiation
during the early-mid afternoon across the central portions of Upper
Michigan and across far western Upper Michigan. As we progress into
the late afternoon-evening hours expect convection to slowly move
eastward as the moisture transport veers west-southwest. Stronger
showers and thunderstorms will gradually diminish as we loose
insolation tonight, but with a couple trailing shortwaves progged to
dig south across the area, can`t rule out additional chances for
lingering showers and thunderstorms overnight.

.LONG TERM...(Saturday through Thursday)
Issued at 511 AM EDT FRI MAY 25 2018

Models suggest that a slowly progressive pattern will prevail
through the middle of next week as a mid/upper level trough over the
wrn CONUS advances toward the plains and the downstream ridge over
the plains shifts through the Great Lakes. Above normal temperatures
will persist through the period although the humidity will be less
oppressive with dewpoints moderating into the upper 40s to lower
50s.

Saturday, a shortwave trough sliding ese from nrn MN combined with
daytime heating boosting inland temps into the mid and upper 80s
with MLCAPE values into the 1000-2000 J/Kg range will support
scattered to numerous shra/tsra. However, confidence in the
locations of greatest coverage is still low given the uncertainty of
low level boundary locations in the light wind regime. 0-6km shear
in the 30-35 knot range will support enough storm organization for a
risk of a few strong storms. Expect sct shra/tsra during the evening
to diminish overnight and slide off to the east as the last of any
trailing weak shrtwvs moves out of the area.

Sunday, weak high pressure is expected to build into the northern
Great Lakes bringing dry but warm weather. Inland high temps will
again climb into the mid to upper 80s. Ling winds will allow
prominent lake breezes to bring cooling along the Great Lakes.

Monday, although another shortwave is expected to brush the region
in the wnw flow pattern, confidence is low with any details. MLCAPE
values to near 1k J/Kg should provide enough instability for at
least isold/sct shra/tsra development in some areas, especially
along lake breeze boundaries.

Tuesday, mainly dry weather is expected but shra/tsra may again
develop over the west near the mid level ridge axis, closest to the
strengthening 1000-850mb theta-e ridge and stronger moisture
advection.

Wednesday-Thursday, a stronger shortwave  and associated sfc low
lifting from the nrn plains into nrn Ontario will drag a cold front
into the northern Great Lakes with an increase in low level moisture
and shra/tsra chances ahead of the front.
&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 141 AM EDT FRI MAY 25 2018

Scattered showers and isolated thunderstorms will move through the
area off and on, although VFR conditions should prevail. LLWS will
continue at all sites overnight. Timing the onset of showers
and thunderstorms will be difficult.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 441 AM EDT FRI MAY 25 2018

Winds less than 20 kts are expected through the middle of next week.
Expect areas of fog to develop and linger at times into the weekend
as multiple rounds of rain are expected over the lake and the humid
airmass lingers. Fog may be dense at times, especially this morning
across the far west half. Thunderstorms are possible today through
Saturday night, and then again early next week.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Dense Fog Advisory until 11 AM EDT /10 AM CDT/ this morning for
     LSZ162.

Lake Michigan...
None.
&&

$$

SHORT TERM...Ritzman
LONG TERM...JLB
AVIATION...07
MARINE...Ritzman



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