Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 171932

Area Forecast Discussion
National Weather Service Marquette MI
332 PM EDT Thu May 17 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...(Friday through Wednesday)
Issued at 302 AM EDT THU MAY 17 2018

Nam shows 500 mb closed low over the mid Mississippi River valley
with a ridge over the upper Great Lakes 12z Fri. This low moves
north and becomes a shortwave over the lower Great Lakes 00z Sun
with more troughing moving through the area on Sun. Still looks like
we will be between systems and widespread rainfall for Sat and Sat
night does not look likely. Having low chance and slight chance pops
in the forecast still looks good. Overall, did not make too many
changes to the going forecast.

In the extended, GFS and ECMWF show a 500 mb trough over the upper
Great Lakes 12z Sun. This upper trough broadens with time and
remains over the area into Thu. Sfc high pressure remains over the
area for most of the period. There is also a weak backdoor cold
front that hangs around the area this forecast period as well that
slowly moves through the area. Looks like there could be some slight
chance pops on Mon and again Tue night into Wed. Temperatures look
to be above normal for this forecast period.

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 129 PM EDT THU MAY 17 2018

VFR conditions will prevail at all TAF sites through the forecast
period. Winds will gradually veer southeasterly this afternoon
and evening. There is a slight chance of wind shear early Friday
morning at KIWD and KCMX but confidence is too low at this point
to include in the TAF package.

.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
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