Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 252233

Area Forecast Discussion
National Weather Service Marquette MI
633 PM EDT Sun Jun 25 2017

.SHORT TERM...(This evening through Monday)
Issued at 348 PM EDT SUN JUN 25 2017

Soggy weather pattern continues through much of the short-term
forecast with heavy rainfall potential expected through late
tonight. There may also be some pea size hail late this afternoon
into early this evening thanks to lower freezing levels.

Tonight: The main focus for heavier rain showers and possibly an
evening thunderstorm will be a strengthening surface trough
continuing to linger across the area along with another strong
shortwave sliding through the area. The stronger shortwave moving
through will help to develop a closed low just southeast of the U.P.
late tonight into Monday morning. The combination of these features
along with ample deep layer moisture/forcing will lead to the
potential for some heavier rain to occur across inland portions of
the U.P. Continued wrap-around moisture and forcing will keep the
rain in the forecast through the overnight hours. This is something
that will need to be watched as many of the basins received an inch
or more of QPF over the past 18 hours; therefore, any heavier rain
that does occur will quickly turn to surface runoff into area
streams and rivers. The greatest threat for this occuring would be
along the WI border into portions of the inland west half of the
U.P. PWAT values are around an inch or more across most of the area
through much of tonight, which again points to heavier rainfall

Monday: The aforementioned shortwave is expected to move very slowly
across the area tonight, in fact, the models still have the
shortwave just south of the U.P. around 12Z Monday. The added upper
level support and surface trough lingering nearby will keep the
chances for rain showers in the forecast through most of the day
Monday.  Again, there may be some heavier rain that occurs with this
system as deep moisture and forcing lingers across the area.
Rainfall potential will be greatest over the east half throughout
the day; however, the west half will see the greatest chance in the
morning and then a very slow decrease in rainfall potential through
the afternoon hours. The additional cloud cover across the area will
help to keep temperatures in the 60s across the U.P. with the
warmest temperatures expected west, where the precip gradually
decreases throughout the day.

.LONG TERM...(Monday night through Sunday)
Issued at 416 PM EDT SUN JUN 25 2017

Ensemble prediction of the pattern this week has changed very little
over the last few days. Mid-level positive height anomalies that
have been over western N America, supporting downstream troffing
over eastern N America, will weaken while expanding ne into n
central Canada this week. This will result in relaxation and
realignment of the eastern N America trof from eastern Canada into
the Northern Plains before the trof shifts across the Upper Great
Lakes over the upcoming weekend. This large scale pattern will
support cool conditions/blo normal temps for Upper MI on most days
this week. Coolest conditions are over the area now and will linger
into Mon as negative 500mb height anomalies max out in the 150-200m
range over the Great Lakes region. Warming will occur into the mid
week period as a rather strong shortwave which is beginning to cut
into the ridge over western Canada goes on to set up troffing from
eastern Canada toward the northern Rockies, backing the flow
downstream. Temps will trend to around normal for a time. Modestly
cooler conditions will then occur into the upcoming weekend as the
upstream trof reaches the Upper Lakes. Model trends over the last
few days are for this late week cooling to be weaker. As for pcpn,
after the current wet period that extends into Mon with the mid-
level trof over the Great Lakes, dry weather returns for Tue as trof
exits well to the e and high pres ridge passes. Shra/tstms will
return midweek as a shortwave passes across the area in the westerly
flow ahead of the approaching trof extending from eastern Canada
toward the northern Rockies. Potential of additional shra/tstms will
continue into the weekend with the possibility of another organized
pcpn event late week/early weekend as the upstream trof arrives. So,
overall, expect a wet week with above normal, potentially excessive,
pcpn amounts. Looking farther ahead, CMC/GFS ensembles indicate weak
troffing developing in the Gulf of Alaska/Pacific NW/western Canada
region next week. Gradually rising heights downstream will lead to
weak positive height anomalies developing across much of the
northern CONUS with pattern more zonally oriented. As a result,
temps during the 1st week of July will trend to at least slightly
above normal.

Beginning Mon night/Tue, as mid-level trof over the Great Lakes
relaxes/shifts e, expect clearing skies Mon night, leading to a
pleasant day on Tue as sfc high pres ridge passes across Upper MI.
Under mostly sunny skies, temps will rise into the 70s across the
area, locally cooler along the Great Lakes. It is noted, however,
that the GFS and to a lesser extent the CMC generate some convection
over the eastern fcst area along lake breeze convergence zone. While
not totally out of the question that there could be isold -shra
given subtle shortwave passing, will retain a dry fcst for now given
the dry look of the NAM/ECMWF.

In developing westerly flow, medium range models remain in good
agreement showing a shortwave approaching the Upper Lakes on Wed.
Although strengthening low-level jet ahead of this wave across the
Plains Tue night will largely remain focused w of Upper MI thru the
night, not out of the question that some shra could reach the far w
before 12z Wed. Shra/tstms will then increase from w to e Wed/Wed
evening as shortwave reaches the Upper Great Lakes. Notable model
trend over the last 24hrs is for the associated sfc low pres to take
a more southerly track. While it now appears that the low will track
w to e across southern Upper MI, it`s possible it may stay just to
the s of the U.P. With precipitable water increasing to 1.5+ inches,
around 200pct of normal, this farther s track significantly raises
the prospect for widespread mdt/heavy rainfall across the area as
warm front will likely not lift to the n of Upper MI. Will be
something to monitor in the coming days given the very wet
conditions over the last 2-3 weeks. Much of the fcst area has seen
pcpn amounts of 150 to 250pct of normal this month, not including
what fell over the last 24hrs. So, hydro concerns could certainly
become an issue if the warm front stays just to the s. As was the
case yesterday, it appears instability will likely be lacking for a
severe risk, especially since model guidance generally points to
considerable coverage of convection thru the warm conveyor into
Upper MI. Severe risk will also be diminished if the warm front
stays s of the area. 12z GFS is now much slower to push the sfc low
pres eastward on Thu due to shortwave deepening and slowing its
eastward progression across the Upper Mississippi Valley. While the
CMC shows this to some degree, see no reason for the wave to slow
down/deepen as much as the GFS shows given the next upstream wave
moving across the northern Rockies. The more consistent ECMWF is
fastest, exiting the sfc low e of the area Thu morning, further
suggesting leaning away from the GFS. Shra will probably linger into
Thu morning with diminishing/ending trend thru the aftn.

Fcst for Fri thru the weekend is quite uncertain. Aforementioned
upstream wave over the northern Rockies will support another sfc low
pres which will track along the boundary lingering back from the
previous wave. Amplitude of the supporting mid-level shortwave will
determine whether that sfc low will track far enough n to bring
another round of widespread, potentially significant, pcpn into
Upper MI. While there have been some model runs suggesting such in
recent days, there is no consistency yet. At this point, based on
yesterday/today`s model runs, it appears the late Fri/Sat time frame
has the best potential of pcpn in the Fri thru Sun period.

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 632 PM EDT SUN JUN 25 2017

IWD will continue to be in the LIFR/VLIFR range overnight with rain
and fog and then improve during the day on Mon as drier air moves
in.  CMX and SAW will see batch of rain showers move in and ceilings
will drop with an approaching disturbance. Fog may also develop over
the TAF sites at times, which may reduce visibility below 4 to 5
miles at times tonight. This disturbance will shift eastward Monday
allowing for a gradual improvement from west to east throughout the
day at both sites.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 348 PM EDT SUN JUN 25 2017

Winds of 10 to 15 knots are expected to continue through the first
half of next week as the pressure gradient decreases and high
pressure builds in for the first part of the work week. Towards the
middle of the week, winds will start to increase to around 20 to 25
knots as a system lifts across the Upper Great Lakes. Winds will
then decrease to around or less than 15 knots towards the end of the
week and next weekend as the pressure gradient relaxes again.

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


LONG TERM...Rolfson
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