Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 220847
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
447 AM EDT FRI JUL 22 2016

.SHORT TERM...(Today and tonight)
Issued at 346 AM EDT FRI JUL 22 2016

Today will continue to be hot with highs in the 80s to low 90s, but
humidity will be lower (bottoming out in the 30-40% range). With a
surface high sitting just southwest of the CWA, overall airmass
moisture will be quite low, so kept a dry forecast in spite of a
couple high-res models showing a spot or two of QPF over the U.P.
this afternoon as a shortwave passes to the northeast of the CWA.

Tonight continues to be quiet with temps dropping into the 60s
(maybe upper 50s interior west).

.LONG TERM...(Saturday through Thursday)
Issued at 446 AM EDT FRI JUL 22 2016

Currently, notable 500mb height anomalies are present for late July
across N America. A subtropical ridge with anomalies as high as 2.5
standard deviations above the long term late July avg dominates a
large part of the CONUS. To the n, an impressively deep mid level
low dominates nw Canada with heights 3.5-4 standard deviations blo
avg centered over nw Nunavut. During the long term, the subtropical
ridge will weaken across the CONUS, and then late next week, there
will be some building of heights near/just off the w coast. Although
heights will remain above normal here, there will be a trend toward
weak troffing into the Great Lakes late next week in response to the
building heights to the w. The mid level low across nw Canada will
also weaken during the long term and will eventually drift n with
time. These 2 main features will help guide a significant shortwave
currently just off the Pacific NW coast eastward to northern Ontario
and the Great Lakes region late Sun. This system will bring the best
potential of shra/tsra during the long term portion of the fcst.
Later next week as shortwaves drop into the developing weak trof,
there will be additional shra/tsra chances. As for temps, above
normal heights thru the period suggest above normal temps will
mostly prevail, especially early on, but there will be gradual
cooling next week toward near near normal for the last half of the
week as weak troffing develops. Looking farther ahead, CPC/NAEFS
outlooks indicate troffing into the Great Lakes may deepen enough to
sustain a cooler period with temps around or even slightly blo
normal in the 8-14day period.

Beginning Sat, the day will begin tranquil with high pres ridge over
the area, then attention turns to the vigorous shortwave trof
currently just off the Pacific NW coast. It will reach the
Dakotas/southern Manitoba Sat evening. In response, strengthening
s/sw flow and resulting waa/ne push of instability ahead of feature
will support shra/tsra across the Dakotas/MN during the day Sat.
While low-level wind max will still be out across MN thru late aftn,
increasing 850mb theta-e advection may bring shra/tsra into far
western Upper MI before 00z Sun. Pres falls spreading into the Upper
Mississippi Valley/western Great Lakes combined with higher pres to
the ne will aid a wind component off Lake Superior during the day,
helping to keep lakeside locations cooler. Will also be a little
cooler near Lake Michigan. Away from these areas, temps should push
well into the 80s on Sat.

As shortwave trof continues eastward and 40kt low-level jet aims
into the Upper Great Lakes, expect shra/tsra to spread across the
area Sat Night/Sun morning. Based on fcst soundings, it appears
convection will be elevated across Upper MI. While axis of greatest
elevated mucape only reaches western Upper MI late in the night,
upwards of 1000j/kg is still avbl. Deep layer shear progs are fairly
noisy, but it appears effective shear may be around 30kt which would
support strong to perhaps isold svr storms though potential should
diminish with eastward extent as storms move farther ahead of the
instability axis. Potential of svr storms may tend to increase late
Sat night over the w as greater instability advects into that area
and then over the e on Sun. If there is any kind of break in
pcpn/cloud cover on Sun before sharp mid level drying arrives and
occluded/cold front passes, mlcape increasing to at least 2000-
3000j/kg combined with 30-40kt of deep layer shear will support a
greater risk of svr storms. If clouds/pcpn dominate up until fropa,
svr risk will be lower. Otherwise, fropa/sharp mid level drying will
result in pcpn ending w to e Sun aftn/evening.

In the wake of the shortwave trof, looks like a couple of dry days
will follow for Mon/Tue. However, confidence in dry weather on Tue
is lower than on Mon as a shortwave swinging thru northern Ontario
could spark some isold convection, particularly as noted with the
ECMWF. Max temps will trend down closer to normal on Mon before
rising a bit for Tue. Dwpts will fall back to the upper 50s/lwr 60s,
still a bit on the uncomfortable side.

Heading into Wed/Thu, uncertainty in timing shortwaves into the
developing weak trof suggests using a consensus of current and
recent medium range guidance to construct pops, resulting in low chc
pops both days.
&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 124 AM EDT FRI JUL 22 2016

Expect VFR conditions to prevail through Friday as drier air moves
into the region. Only issue will be gusty westerly winds early this
evening and again on Friday especially at the more exposed CMX
location where gusts could exceed 25 knots.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 346 AM EDT FRI JUL 22 2016

Expect winds to hold below 20 kts through the forecast period under
a relatively weak pressure gradient and high overwater stability.
Patchy fog is possible late in the weekend as another humid airmass
moves over the Upper Lakes.
&&

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

$$

SHORT TERM...Titus
LONG TERM...Rolfson
AVIATION...Voss
MARINE...Titus



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