Area Forecast Discussion
Issued by NWS Marquette, MI
FXUS63 KMQT 242334
Area Forecast Discussion
National Weather Service Marquette MI
734 PM EDT SUN JUL 24 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...(Monday night through Sunday)
Issued at 304 PM EDT SUN JUL 24 2016
Decent agreement continues in overall look of upper level pattern
into next weekend. However, there still are model differences for
late this week into next weekend regarding position of shortwave
trough/sfc low and associated rain chances. Troughing that develops
early this week more or less persists at various amplitude through
the period. After a cool day on Mon could sneak in a warmer day Tue
ahead of a cold front that drops across Upper Great Lakes Tue night
into Wed. Temps should end up at or blo normal for the rest of the
week into next weekend, especially near Lake Superior with rather
persistent north-northeast winds.
Mon Night sfc high pressure slides across large area from northern
plains to Upper Mississippi river valley to the Great Lakes. PWAT
low enough for interior cool spots to drop into the low 50s while
shoreline locations stay in the 60s.
On Tue wnw flow aloft could brings in slightly falling heights but
at least now there is not any real shortwave to latch onto. Moisture
advection h7-h5 is main driver for rain showers moving into western
U.P. in the aftn. If there ends up being minimal shortwave energy
moving through, most day could end up dry with increasing mid-high
clouds from west to east. Cold front works through on Tue night.
Hints that stronger shortwave may move across as well. Should see
increase in shower chances on Tue night and with Upper Great Lakes
on edge of steeper mid level lapse rates there will be conditional
thunderstorm potential especially if stronger shortwave is crossing
the area. Front continues its passage across Upper Michigan on Wed.
Wind field is light so there may be lake breezes as front works
through. If fropa timing is slower as shown by GFS and ECMWF the
additional convergence and mlcapes up to 1000j/kg support increased
chances of showers and some thunderstorms as well. Effective shear
maybe up to 30 kts so likely not looking at severe storms.
Front settles across mid Mississippi river valley into the Lower
Great Lakes and northern Ohio Valley by Thu morning taking the
chances of rain with it. GFS shows stronger shortwave working
through Wed night into Thu morning so it is slower to clear out the
frontal zone and keeps pops lingering through at least Thu morning.
Cannot completely rule that out so will keep slight chances at that
time. High pressure then builds in for Friday while a sfc low
pressure wave slides across the lower Great Lakes and Ohio Valley
along slowing frontal boundary. Intstability will stay tied into the
low pressure wave and south of the increasingly stationary front
while airmass over Upper Great Lakes will be cooler and drier. Dry
weather should hold through Sat before the high moving east of the
region results in return flow bringing start of a warming trend
along with chances of showers and thunderstorms.
Caveat in this thinking is that 12z ECMWF now looks a bit more like
previous runs of GFS by showing deeper and farther north shortwave
trough and sfc low late Thu into Fri and maybe even into Sat. Result
would be rain could impact at least east half of cwa Fri into Sat.
For now, the forecast will stay dry for these time frames as that 12z
ECMWF run is quite inconsistent with its previous run.
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 734 PM EDT SUN JUL 24 2016
VFR conditions to prevail through the forecast as the cold front
continues to move through central and eastern Upper Michigan. Winds
will diminish with the gusts ending by 3Z but gusts will return
with daytime mixing on Monday. Strongest gusts...up to 23 knots...
forecast at KCMX tomorrow with lower gusts at KIWD and KSAW.
.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