Area Forecast Discussion
Issued by NWS Marquette, MI
FXUS63 KMQT 201934
Area Forecast Discussion
National Weather Service Marquette MI
334 PM EDT WED JUL 20 2016
.SHORT TERM...(Today and tonight)
Issued at 435 AM EDT WED JUL 20 2016
The upper ridge and convectively induced shortwave moving along the
northern edge of the ridge continue to thwart the forecast process.
Ended up knocking POPs down significantly for today as the shortwave
previously anticipated to be moving out of MN completely dissipated.
Models now have some isolated convection this afternoon/early
evening firing mainly over western Upper Michigan as residual
shortwave energy passes. Models suggest SBCAPE of 2000-3000 J/kg and
effective shear around 30 KTS, so any storms that do develop could
quickly become strong to possibly severe. Partly cloudy skies are
expected, mainly from thin, high clouds leftover from upstream
convective. 850mb temps will increase to 21C west, 19C east, by this
evening, and that warm airmass will allow for temps to climb up to
90F over portions of the west half. Over the east half, south winds
will keep areas downwind of Lake Michigan cooler but mainly still in
Lots of uncertainty tonight as models suggest a couple shortwaves
could move through. The first shortwave looks to provide better
chances for scattered convection, but the second could produce
widespread convection that may be strong to severe, but that would
mainly occur during the first part of the long term forecast (see
long term for more details). Lots of issues to be resolved for the
forecast for tonight, but those will probably not be easily
determined until around 6 hours out due to shortwave energy.
.LONG TERM...(Thursday night through Wednesday)
Issued at 333 PM EDT WED JUL 20 2016
A mean upr rdg wl bring above normal temps to the area thru this
weekend. After lingering showers/TS end on Thu evng, a sfc hi pres
wl bring dry wx to Upr MI late Thu ngt thru most of Sat. A strong
upr disturbance pushing ewd thru the Upr Lks is then likely to bring
more showers/TS Sat ngt into Sun, and some of these storms could be
severe. Cooler and drier air wl follow this disturbance early next
Thu ngt...Expect lingering showers/TS over mainly the SE half of the
CWA to diminish in the evng with passage of weak cold fnt, arrival
of mid lvl drying, dnva, deep lyr qvector dvgc and nocturnal
cooling. PWAT is fcst to dip as lo as 0.5 inch late at ngt, so skies
should turn clr with the aprch of sfc hi pres/acyc llvl flow. Min
temps may bottom out as lo as 60 over the interior W.
Fri/Fri ngt...Warm but relatively dry airmass/sfc hi pres are fcst
to dominate this period just to the E of upr rdg axis over MN. H85
temps are fcst to be 18-20C on Fri aftn, supporting max temps at
least close to 90 away fm lk moderation that wl be favored near Lk
Sup with llvl WNW flow. This downslope flow wl accentuate the wrmg
over the scentral, where max temps may reach close to 95.
Fortunately, dry airmass wl support sfc dewpts mixing out into the
50s where the temps wl be warmest. Although models hint some hi clds
may return over the W on Fri ngt, some interior locations could see
temps fall into the upr 50s with lgt winds.
Sat...A strong shrtwv is fcst to push into the nrn plains on Sat,
supporting deepening lo pres in the nrn plains. In general, models
have tended to slow down the ewd progression of this disturbance, so
most of the guidance hints the day on Sat wl be dominated by sfc hi
pres shifting slowly to the E and thus remain dry despite more
hi/mid clds drifting into the area ahead of the lo pres/warm fnt.
Did retain some chc pops over the W to account for the faster
guidance. Although these clds wl tend to cap max temps a bit, most
places wl see temps rising well into the 80s and a trend toward more
humidity with strengthening SSE flow. Locations downwind of Lk MI
should be a bit cooler with the llvl SSE wind.
Sat ngt/Sun...This period looks like the best chc for some
showers/TS as potent shrtwv moves to the E, accompanied by sfc lo
pres in Ontario/attended occluded fnt/axis of pwat aoa 2 inches.
Considering the strength of the disturbance and ribbon of strong mid
lvl winds/h5 winds fcst up to 60kts/ as well as plentiful mstr and
instability with SSI fcst aob -5C, some of the stronger storms could
be severe even if they are elevated in nature to the N of warm fnt
that may remain to the S of Upr MI. Pops should diminish over the W
beginning in the aftn with arrival of drier air behind the occluded/
cold fropa. Temps wl run above normal during this time.
Extended...After lingering showers/TS end over the E on Sun evng, a
cooler airmass wl dominate on Mon/Tue with h85 temps falling as lo
as 12C. Although some of the medium range guidance hints there could
be at least some bkn clds and even a few showers on Mon under a
sharper cyc NW llvl flow left in the wake of the departing sfc lo
pres, most of this time should be dry. Depending on how quickly
another disturbance aprchs fm the W toward mid week, more showers/TS
could arrive Tue ngt/Wed.
.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 206 PM EDT WED JUL 20 2016
VFR conditions expected through the TAF period. Details for this TAF
issuance are difficult to pin down with exact timing of any showers
and thunderstorms being dependent on timing and track of
disturbances sliding into the area. Overall confidence in any one
solution is fairly low, so have decided to leave out of the TAF at
this point. There could be a couple of isolated showers and
thunderstorms this evening, but chances are minimal. The chance for
showers and thunderstorms will slide in very late tonight, but the
best potential for showers and thunderstorms will be toward the end
of the TAF period as a weak cold front passes through the area.
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 333 PM EDT WED JUL 20 2016
Expect winds to hold below 20 kts through the forecast period under
a relatively weak pressure gradient and high overwater stability.
Warm and humid air will flow across Lake Superior on tonight through
Thu, which will allow fog to form, locally dense at times. More fog
is likely late in the weekend as another humid airmass moves over
the Upper Lakes.