Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 141934 CCA

Area Forecast Discussion
National Weather Service Marquette MI
319 PM EDT Mon Aug 14 2017

.SHORT TERM...(This evening through Tuesday)
Issued at 226 PM EDT MON AUG 14 2017

Upper air pattern consists of a 500 mb trough over the upper Great
Lakes today with a shortwave ridge moving in for Tue. Nam shows some
850-500 mb q-vector convergence along with some moisture moving
through the area this afternoon before both move out tonight.
Looking at KMQT radar, a cyclonic spin with a MVC is moving across
the western cwa this afternoon into this evening. This will continue
to produce showers as it slowly moves across and have pops in the
likely to chance category as this moves through. There could also be
some lake breeze convergence showers in the east as well. For
tonight, the showers move south of the area and with light winds,
decent radiational cooling possibilities will set up and went below
guidance for low temperatures. Tue looks quiet and dry. Did not make
too many changes to the going forecast overall.

.LONG TERM...(Tuesday night through Monday)
Issued at 319 PM EDT MON AUG 14 2017

The main forecast concern arrives later this week, late Wednesday
through Friday, as a system develops in the lee of the Rockies and
lifts northeast across the Upper Great Lakes region. This weekend
looks mostly dry with temperatures warming into the 70s, and
possibly lower 80s in some locations.

Tuesday night with high pressure anchored east of Lake Superior,
expect dry conditions to prevail. Mostly clear skies across the
central and east will likely allow temperatures to drop down into
the upper 40s in some spots. The focus then turns on the approaching
storm system. Medium range models have come into much better
agreement with slowing this system down, along with taking a more
northern track, which makes sense as the main upper-level wave lifts
across the Upper Great Lakes. In fact, the 12Z ECMWF shifted the
track of this system about 150 to 200 miles north compared to its
previous run. All that being said, confidence is increasing that the
majority of Wednesday should remain dry, with the exception of far
southwest portions of Upper Michigan as warm air advection begins to
lift into the region. Late Wednesday night through Thursday
afternoon, as the surface low lifts into western parts of Upper
Michigan, moisture transport will ramp up along and across the warm
sector leading to the development of fairly widespread showers and
thunderstorms. With PWATs progged to increase to around 1.5-2.0
inches, a deep warm cloud layer, and moisture transport taking aim
on the area heavy rain will be possible, although right now the
placement of the heaviest rain remains a bit uncertain. Also, as
this system moves into Upper Michigan, the surface pressure gradient
will increase overnight with gusty southwest winds possible. During
the afternoon and evening hours on Thursday, the surface low is
expected to track across Upper Michigan; therefore, some locations
may see an end to precipitation as a slot of dry air wraps around
and into the system. Depending on how cloud cover evolves, we could
see another round of showers/storms as the cold front and triple
point pushes across central portions of Upper Michigan on Thursday

Thursday night into Friday, as the surface low begins to exit Upper
Michigan lingering showers should lift off to the northeast, with
breezy north-northwesterly winds. Through the day on Friday,
onshore, upslope flow will likely result in cloud cover for much of
the day. These clouds combined with cold air advection behind the
exiting system will keep temperatures down on Friday, so have
lowered temperatures a bit, especially along the northern portions
of the area.

This weekend high pressure will take hold on the area bringing back
warmer temperatures, the return of sunshine, and drier weather.
Temperatures will warm throughout the weekend, with some locations
possible reaching the low 80s by the end of the weekend. Early next
week chances for showers and storms will return as a trailing cold
front is progged to push east across the area.

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 107 PM EDT MON AUG 14 2017

Showers will be moving across portions of Upper MI, especially
around KIWD. Certainly possible that conditions could fall to MVFR
at times during periods of shra at KIWD this afternoon. As shra
depart tonight and clouds begin to clear out, radiational fog should
develop. KIWD is most likely to see denser fog with potential of
VLIFR conditions late. While KSAW is likely to fall to MVFR late.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 226 PM EDT MON AUG 14 2017

Winds less than 20 kts into Wed with high pressure overhead, then SE-
E winds increase to 15-30 kts late Wed into Thu as a low pressure
system crosses the Upper Great Lakes. Strongest winds, with gusts to
30 kts, will be over western Lk Superior Wed aftn into Wed evening
then shifting to eastern Lk Superior late Wed night into Thu
morning. NW winds behind the low could then reach 20 kts late Thu
into Fri, strongest over east half of Lk Superior. Winds diminish to
20 kts or less next weekend as high pressure builds back overhead.

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


LONG TERM...Ritzman
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