Area Forecast Discussion
Issued by NWS Marquette, MI
FXUS63 KMQT 231940
Area Forecast Discussion
National Weather Service Marquette MI
340 PM EDT TUE AUG 23 2016
.SHORT TERM...(This evening through Wednesday)
Issued at 340 PM EDT TUE AUG 23 2016
12Z raobs/latest WV imagery and RAP analysis show a bldg upr rdg
over the western Great Lks/Ontario downstream of troffing across the
nrn Rockies/Wcentral Canada. Although there were a few showers over
the ern cwa this mrng, strong capping shown on the 12Z INL/MPX/GRB
raobs and a push of relatively dry llvl air into the Upr Lks within
gusty SW winds btwn sfc hi pres in the mid-Atlantic states and a lo
pres in the nrn Plains to the E of the upr trof are resulting in
mosunny wx over Upr MI this aftn. With h85 temps aprchg 20C, sfc
temps away fm moderation off Lk MI have risen well into the 80s.
There is another shrtwv lifting NEwd thru NW Iowa in the SW flow alf
ahead of the Rockies trof causing a cluster of showers/TS moving
toward srn MN.
Main fcst concerns in the short term fcst period focus on pops
associated with shrtwv aprchg fm the SW.
Tngt...This evng wl be dry/just some hi clds ahead of shrtwv to the
SW with a capped environment still in place. But later tngt, shrtwv
to the SW is fcst to move into WI by 12Z. With incrsg mid lvl mstr/
h85 theta-e advctn/some weak dpva and deep lyr qvector cnvgc
arriving near the WI border late ahead of this feature, expect the
return of more clds and at least some sct showers near the border
toward sunrise. The combination of steady SW winds/incrsg clds wl
result in well above normal min temps in the 60s, with readings in
the downslope locations near Lk Sup probably falling not much blo 70.
Wed...Shrtwv in WI is fcst to drift NEwd thru Scentral Upr MI/nrn Lk
MI and to near nrn Lk Huron by late in the day. The track of this
disturbance/sharper deep lyr forcing and h85 theta-e advctn favors
mainly the SE half of the cwa for the hier pops. Modest h7-5 lapse
rates fcst aob 6-6.5C/km and a good deal of cld cover that wl limit
sfc heating/max temps mainly in the 70s favor only a few embedded
TS. Mid lvl drying in the wake of the shrtwv wl then result in
diminished pops over the W, but concerns about at least some sfc
destabilization with thinning clds ahead of slowly aprchg sfc cold
fnt associated with Rockies trof warrants at least some lo chc pops.
But the drying/subsidence left in the wake of the departing
disturbance and ahead of any forcing with the shrtwv tracking E just
N of the Cndn border wl limit the potential for these additional
.LONG TERM...(Wednesday through Monday)
Issued at 459 AM EDT TUE AUG 23 2016
Models suggest that a progressive pattern will prevail with a
mid/upper level low/trough over srn Sask/Manitoba Wednesday that will
move to nrn Ontario Thursday. This will bring increasing shra/tsra
chances Wednesday as the sfc trough/front moves toward the region.
Cooler and drier weather will then build into the nrn Great Lakes from
Thursday into Friday as high pressure builds from the nrn plains into
the Great Lakes. Unsettled weather returns by the weekend as the low
amplitude pattern will allow another mid level trough to move into
Wednesday and Wednesday night, as the sfc trough moves closer to the
area expect shra/tsra chances to increase as moisture advection
bring PWAT values above 1.5 inches. There is still considerable
uncertainty with the timing/position/strength of any convectively
modified shortwaves emerging from the plains that will help support
the pcpn. However, models have trended toward the idea that the
shra/tsra with a shrtwv will move in to mainly the srn cwa in the
morning and over the east in the afternoon. With the thicker clouds
and pcpn moving in during the morning instability (MLCAPE values into
the 500-1000 J/Kg range) and shear(0-6km 25 to 30 knots) will be
marginal for any stronger storms. The pcpn chances will shift to
mainly the ern cwa by late afternoon and evening. There still could
be some lingering isold/sct shrat/tsra over the west as the sfc
trough approaches if instability recovers during the afternoon.
Thursday into Thursday night, a trailing secondary cold front and
shrtwv could bring some isold -shra into wrn cwa Thursday night.
Otherwise, cooler air and drier air will prevail with highs from the
upper 60s west to mid 70s south and east and dewpoints falling into
the mid 50s.
Friday-Monday, surface high pressure and upper ridging will then
bring dry and mostly clear conditions Friday into early Saturday.
With a continued progressive pattern, pcpn chances will increase as
models suggest potential for a shrtwv to bring another round of
shra/tsra toward the area from later Saturday into early Sunday with
clearing/drying Sunday into Monday. However, confidence in any
details is low given models differences and lack of consistency.
.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 143 PM EDT TUE AUG 23 2016
Since gusty SW winds are drawing relatively dry air into Upr MI,
expect VFR conditions to be the rule at the TAF sites until at least
late tngt. The gusty winds, especially at IWD and SAW, will diminish
arnd sunset with the loss of daytime heating/mixing. Later tngt, the
SSW flow wl tape some moister llvl air ahead of an aprchg
disturbance. The combination of this mstr advection as well as
moistening fm -shra that fell ahead of the disturbance wl result in
deteriorating conditions into the MVFR range on Wed mrng, especially
at IWD and SAW where there is a better chc for the -shra. Not out of
the question there could be some IFR cigs at those locations.
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 340 PM EDT TUE AUG 23 2016
S to SW winds up to 20 kts will persist thru Wed ahead of an
approaching cold front. Winds will shift to the W following the
frontal passage on Wed night and then increase up to 25 kts on Thu
as the gradient tightens a bit. As trailing hi pres approaches and
the gradient slackens, winds will veer to the NW and diminish to
under 15 kts on Fri. Expect SE winds up to 20 kts to prevail over
the weekend between the departing hi pres and a lo pres approaching
from the SW.