Area Forecast Discussion
Issued by NWS Marquette, MI

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173
FXUS63 KMQT 191918
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
318 PM EDT Thu Oct 19 2017

.SHORT TERM...(This evening through Friday)
Issued at 318 PM EDT THU OCT 19 2017

...Dry and breezy conditions will lead to elevated fire weather
conditions into early evening...

Dew points mainly in the lower to mid 20s this afternoon have led to
rh values close to 20 pct with elevated fire weather concerns.
Fortunately, wsw winds haven`t been overly gusty with only a few
inland locations reaching 20 mph or greater. Over the Keweenaw, west
winds have been a bit more gusty in the 25 to 30 mph range. Temps
under partly cloudy skies have been generally in the lower 60s.
Winds will continue to subside later this afternoon with diminished
mixing.

Tonight, return flow will develop across the area as surface high
pressure tracks east and a developing surface low in the lee of the
northern Rockies in Canada becomes established. This moister return
southerly flow will push the drier air out the region overnight, so
dew points should be on the rise. The combination of better mixing
from southerly gradient winds and increasing low-level moisture will
result in fairly mild overnight lows from the lower to mid 40s
inland central and east to the upper 40s to lower 50s west and
near the Great Lakes.

Friday, warm advection southerly wind flow under mostly sunny skies
and mixing of 15-16c 900-925 mb temps to sfc will result in max
temps in the lower to mid 70s west half.  Lake moderation off Lake
Mi in southerly flow will keep temps a bit cooler east half
(generally in the upper 60s).

.LONG TERM...(Friday night through Thursday)
Issued at 318 PM EDT THU OCT 19 2017

Friday night: High pressure will slowly slide off to the east of the
area. As this happens, moisture will steadily return to the area
ahead of an approaching cold front. The main impact this will have,
is an increase in cloud cover from the west. There may be a few rain
showers that slide into the far western U.P.; however, dry air in
the mid levels will limit the chances. Lows will be a bit warmer
with southerly flow as most areas will be in the 50s.

Saturday into Sunday: An upper level trough is expected to slide
from the Plains eastward through the Upper Great Lakes region
through this time period. At the surface, the associated strong
surface low is expected to slide north of the area, and remain
mainly over Canada. This will drag a cold front through the Upper
Peninsula Saturday afternoon and night and then to the east of the
area by Sunday evening. Increased moisture and forcing ahead of the
front will allow for widespread rain showers to spread across the
U.P. Current model trends have roughly a half inch of precip across
the area by the time the precipitation ends late Sunday afternoon.
There may be just enough instability around for Saturday afternoon
and Saturday evening ahead of the front for a few thunderstorms;
however, thunderstorm potential does look to be fairly marginal
overall. Temperatures will be about 10 to 15 degrees above normal
through this time period.

The rest of the extended: There will likely be a brief break in the
precipitation Sunday night as a brief ridge builds into the area;
however, another slow-moving low pressure system is expected to
slide through for Monday through Wednesday. Aloft, a much deeper
trough will dig into the Upper Great Lakes region. This will allow
enough cold air to slide into the region to cause some snow to mix
in with the rain over the higher terrain of the west. The ground is
still warm and overall QPF is not expected to be that impressive, so
not expecting too much in the way of accumulation. 850mb
temperatures are progged to drop into the -5C to -7C range
(according to the GFS with the EC being about 5 degrees warmer),
creating delta-T values in the 17 to 19C range, depending on how
much cold air is drawn into the area. This will be prime for lake
enhancement. The favored areas will have to be pinned down as models
come into better agreement, but it looks like the northwest wind
lake effect prone areas would have the best chance at this point.
Thursday, the EC is hinting at continued troughing aloft with cooler
air, while the GFS is trending more toward a warming/ridging pattern
across the area. Model consensus was used and unaltered for this
time period.
&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 109 PM EDT THU OCT 19 2017

VFR conditions are expected to prevail over the next 24 hours. The
main aviation concerns will be gusty westerly winds at KCMX this
afternoon, and then low-level wind shear developing at all sites
tonight.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 318 PM EDT THU OCT 19 2017

Winds have diminished blo gales this afternoon and will continue to
diminish this evening. Tonight winds will subside to around or less
than 25 knots. Friday through Monday, winds will remain mostly
between 20 and 25 knots.
&&

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

$$

SHORT TERM...Voss
LONG TERM...KEC
AVIATION...Voss
MARINE...Voss



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