Area Forecast Discussion
Issued by NWS Marquette, MI
FXUS63 KMQT 250824
Area Forecast Discussion
National Weather Service Marquette MI
424 AM EDT MON JUL 25 2016
.SHORT TERM...(This evening through Monday)
Issued at 336 PM EDT SUN JUL 24 2016
12Z raobs/latest wv imagery and RAP analysis show strong shrtwv over
far NW Ontario edging slowly to the ENE. Attendant occluded/cold fnt
is over the wrn cwa, roughly fm Baraga into Iron River, and shifting
to the E. Despite the very humid airmass in advance of this fnt
/12z pwat was 2.02 inch at GRB/, aggressive dry slotting on the srn
flank of the Ontario disturbance and associated with the very capped
environment depicted on the 12Z MPX raob, where the 12Z h7 temp was
13C and h7 W winds were 35 kts, have prevented the development of
any deep convection ahead of this fnt thru 19Z. Lo clds, especially
SE of a line from Iron Mountain to Munising, have also held back sfc
destabilization. SPC mesoanalysis shows MLCIN associated with this
cap still at 75 j/kg or hier even where more breaks in the clds have
dvlpd over central Upr MI ahead of the fnt and lifted MLCape up to
1000j/kg. Current radar does show a line of returns fm about Sawyer
Airport to Iron Mountain near the axis of hier MLCape, but
reflectivity returns are weak. Looking upstream, sfc dewpts are
falling into the 50s over MN as much drier air shown on the 12Z
Aberdeen and Bismarck raobs /pwat arnd 0.75 inch/ pushes into the
Late this aftn...Although many of the models generate showers/TS
over the central cwa late this aftn/evng, suspect sgnft mid lvl
drying/capping wl suppress deep convection. But have retained some
lo chc pops ahead of the passing fnt into early this evng over
approximately the E half of the cwa. Best chc for this convection
appears to over ern Marquette into wrn Alger Counties where there
has been more sunshine. Given presence of mid lvl dry air that would
enhance dcape as well as ribbon of strong mid lvl winds within the
dry slot, any storm that does break the cap could turn severe. Given
the persistence of lo clds over the SE cwa, any showers/TS that do
dvlp wl likely weaken as they move into this area/lower MLCape.
Tngt...Strong shrtwv now over NW Ontario is fcst to drift ewd to
near James Bay by 12Z Mon, with cold fnt clrg the ern cwa arnd 00Z.
If there are any showers/TS over the E, these should end by arnd 00Z
under continued surge of mid lvl drying in its wake. Although
guidance hints another weak disturbance dropping thru the incrsgly
NW flow alf may pass late tngt, absence of deep mstr under deep lyr
subsidence/qvector dvgc in the wake of the departing stronger shrtwv
wl limit the impact to some sct clds.
Although cooler/drier air, with h85 temps near 12C fcst by 12Z, wl
arrive during the ngt, steady W winds under tight pres gradient btwn
departing lo and sfc hi pres bldg toward MN wl limit the diurnal
Mon...Sfc hi pres under aprchg shrtwv rdg axis/larger scale DNVA and
subsidence wl bring dry wx. Other than some diurnal cu that dvlp
under weak h85 thermal trof, the day wl feature a good deal of
sunshine. H85 temps are fcst arnd 14C, supporting max temps over the
interior into the 80-85 range, warmest over the scentral with
downslope WNW h925 wind. One concern is that the only slowly
diminishing NW flow wl build Lk Sup waves sufficiently to cause a
moderate to hi swim risk along the beaches E of Marquette.
.LONG TERM...(Tuesday through Sunday)
Issued at 424 AM EDT MON JUL 25 2016
Tuesday through Wednesday night: A cold front is progged to sag
southward from Canada, Tuesday morning, into the Upper Great Lakes
Region Tuesday night as surface high pressure slides to the east.
Southerly flow on the back side of the high will help to increase
moisture into the area. This, along with forcing along and ahead of
the front, will provide chances of showers and thunderstorms for
most of the CWA through that time period. As the weak cold front
slides to the south of the area Wednesday and Wednesday night, the
better chances for showers and thunderstorms will also slide south
and linger over northern WI and possibly along the Upper MI/ WI
border. MUCAPE values are progged to be between 1000-1500 J/kg
Tuesday afternoon/evening and around 500-1000 J/kg Wednesday
afternoon/evening. The severe weather potential looks low at this
point, through this time period, as the system will lack any major
dynamical support, keeping shear values around or below 25-30 knots.
The storm mode would likely be more of a pulse thunderstorm mode
during the afternoon/evening hours on both Wednesday and Thursday.
Some of the the storms Tuesday afternoon/evening may pulse up and
become strong for a brief period of time, but organized severe
weather is not expected. The main threat from any of the stronger
storms would be small hail and gusty winds.
Thursday through Friday night: High pressure and dry air is progged
to slide into the area from Canada by Thursday afternoon and then
linger through this time period. Aloft, the Upper Great Lakes region
will be under a slight troughing pattern to near zonal flow. This
flow along with fairly dry air in place will keep the bulk of the
precipitation to the south of the U.P., while also helping to keep
temperatures closer to slightly below normal for this time of year.
Normal highs are right around 77 while normal lows are around 55.
There is a 500mb shortwave that is progged to slide just south of
the U.P., mainly across WI, Thursday afternoon and evening. At this
point, the main impact for the U.P. would be an increase in cloud
cover along the WI border with perhaps a slight chance of showers
for the south half of the U.P.
Saturday through the extended: The aforementioned high pressure
system will slide to the east of the area through this time period.
As this happens, warmer and more moist, southerly flow will return
to the Upper Great Lakes region. Aloft, it looks as if there may be
a couple shortwaves that slide across the area, bringing small
chances for showers and thunderstorms. Exact details are tough to
pin down this far out, but it does look like the CWA could see
showers and thunderstorms, with the best chances occurring during
the afternoon hours each day through this time period. Confidence is
low enough at this point to stick with only low chance pops.
.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 129 AM EDT MON JUL 25 2016
VFR conditions to prevail through the forecast. Only issue is for
gusty winds to 23 knots over KCMX during the late morning through
the afternoon hours with mixing of the boundary layer and some weak
cold air advection. KSAW will also see some gusty conditions but
should stay below 20 knots. Winds to slacken in the late afternoon
with high pressure building in.
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 304 PM EDT SUN JUL 24 2016
In the wake of a cold front pushing across Lake Superior this aftn,
w winds of up to 20kt with gusts to 25kt are expected into Mon.
These stronger winds will diminish by Mon evening. Winds for the
remainder of the fcst period will mostly 15kt or less. Any fog
patches will diminish later this evening with the arrival of drier