Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 172339

Area Forecast Discussion
National Weather Service Marquette MI
739 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 night through Thursday)
Issued at 337 PM EDT THU MAY 17 2018

The main forecast concern in the extended will be the elevated fire
weather potential for much of next week as little to no rain
is expected.

Beginning Fri night, gradient between high pressure centered near
New England and the low pressure trough/front incoming from the
northern Plains will induce S-SE boundary layer winds of 15-25
knots, especially across the northern tier of the fcst area. The
winds will keep low-levels well mixed and min temps somewhat higher
than normal. Expect lows mainly in the 40s with some lower 50s near
the Lake Superior shore far west. Due to the mixing, RH recovery
will also be somewhat poor, generally less than 75 pct across the
northern tier of the cwa.

Attention then turns to trough/cold front expected to move through
the fcst area Sat afternoon and evening. With models indicating the
better forcing staying north and south of the front as it moves into
the area and NAM fcst soundings indicating shallow moisture to only
around 4 kft, coverage of any showers that form in a narrow line
along behind the front would be isolated at best. Will maintain no
more than low chc (20-30%) pops Sat afternoon into evening.

Next week will be fairly dry as models maintain split flow pattern
across the western half of the CONUS and a confluent nw flow into
the Upper Great Lakes region. Although winds will remain fairly
light across the area under persistent sfc high pressure, daytime
minimum RHs will continue to be fairly low (20-30% range) through
much of the week, heightening fire weather concerns in this
persistent dry pattern. Unfortunately, the next best chance of
precipitation looks like it won`t be until late next week (at the
earliest) as a shortwave trough moves in from the Northern Plains.

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 738 PM EDT THU MAY 17 2018

VFR conditions will prevail at all TAF sites through the forecast
period. A period of LLWS is expected at KIWD as a southerly low
level jet develops above the low level inversion.

.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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