Area Forecast Discussion
Issued by NWS Marquette, MI
FXUS63 KMQT 171134
Area Forecast Discussion
National Weather Service Marquette MI
734 AM EDT Mon Oct 17 2016
Issued at 432 AM EDT MON OCT 17 2016
00Z raobs/latest wv imagery and RAP analysis show a potent shrtwv
lifting newd thru the nrn plains toward Lk Winnipeg, accompanied by
12hr h5 hgt falls aprchg 100m. Strong llj with h85 s winds up to
50kts over MN and vigorous theta-e advctn/isentropic ascent/steep
mid lvl lapse rates shown on the 00Z MPX raob in advance of this
feature and warm fnt moving thru the Upr Midwest is causing an area
of showers/TS over the wrn Great Lks into wrn Upr MI. A few of the
storms turned strong, producing marginally svr hail at Rockland in
Ontonagon County. There is a break in the pcpn over the nrn Plains
under the influence of drier mid lvl air depicted at h7, but another
shrtwv lifting into the nrn Rockies is causing an area of colder cld
tops/pcpn to aprch the nw Plains.
Main fcst concerns in the short term focus on pop/convective trends
tday associated with vigorous waa ahead of shrtwv lifting into
scentral Canada. As the shrtwv now aprchg the nrn Rockies aprchs
tngt, focus wl shift to pops/convection associated with that feature.
Today...Band of showers/TS under llj/axis of deep lyr qvector cnvgc/
mucapes up to about 1000-1200 j/kg wl move e acrs the area this mrng
with this dynamic forcing before arrival of mid lvl drying/
stabilization in the wake of the sharper forcing results in
diminishing pops w-e thru the day. Considering the instability and
effective lyr shear within the elevated convection, not out of the
question some of the storms this mrng could cause some svr hail. The
best chc for some lingering showers/TS thru the day wl be over the
scentral, where the aprchg warm fnt is fcst to stall out. H85 temps
are fcst to peak arnd 15C over the far scentral, but plenty of
lingering lo clds wl hold down max temps. Still, max temps arnd 70
with dewpts over 60 wl make the day feel warm and humid.
.LONG TERM...(Tonight through Sunday) Issued at 451 AM EDT MON OCT
Busy morning watching convection and shuffling of duties, so will be
brief and hit the highlights. Nam shows a broad 500 mb trough over
the western U.S. 12z Tue with a shortwave over the upper Great
Lakes. The broad trough in the western U.S. heads east and carves
out a deep trough in the upper Great Lakes by 12z Thu. GFS and ECMWF
show about the same thing as well. Overall, did not make too many
changes to the going forecast for temperatures. As for pops, have
categorical in for tonight in the evening with second wave moving
through and then clear it out pretty rapidly with drying Tue
morning. Dry weather continues then into Wed night.
In the extended, GFS and ECMWF show a deep 500 mb trough over the
central U.S. 12z Thu with 850 mb temperatures over Lake Superior
around -3C. This upper trough continues to dig into the ern U.S. 12z
Fri with 850 mb temperatures across Lake Superior remaining around
-3C. A 500 mb ridge then starts to build into the desert sw 12z Sat
with a shortwave that moves to the north of the upper Great Lakes.
Broad troughing then continues over the upper Great Lakes into Sun.
Temperatures look to stay near normal for this forecast period.
.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 733 AM EDT MON OCT 17 2016
Although the larger area of showers and TS have moved off to the e
of the TAF sites, lingering llvl mstr to the n of an aprchg warm fnt
wl allow plenty of lo clds to linger. The best chc for persistent
IFR cigs wl be at SAW, where the llvl sse wind wl upslope. Enuf dry
air may reach the w to allow for at least marginal VFR conditions at
IWD and CMX this aftn. As another disturbance aprchs late today/
tngt, another area of showers wl overspread the area. A TS wl be
psbl, mainly at SAW and IWD closer to a stnry fnt over srn Upr MI.
Conditions wl deteriorate into the LIFR range at all the TAF sites.
A wshft to the wnw in the wake of this disturbance wl draw some dry
air into the area and allow for an improvement to MVFR by late tngt.
The one exception wl be at CMX, where the llvl flow wl present a
sharper upslope wind component and allow IFR cigs to linger thru 12Z.
.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 451 AM EDT MON OCT 17 2016
Two gale events for this forecast period. First one is happening now
early this morning with easterly gales out ahead of a warm front and
winds rapidly came up early this morning across the west. These
winds come down fairly quickly. A low pressure system will move
northeast near into Upper MI tonight. This will allow strong
northwest winds to gust up to 30 kts to develop in its wake, mainly
over eastern Lake Superior, before weakening to about 20 kts or less
Tuesday night thru Thursday as high pressure approaches. This will
have to be watched though as there could be a very brief period of
some gale force gusts behind this low as a tight pressure gradient
occurs and would not be surprised to have a second event gale for a
short period of time across the eastern lake tonight.
Gale Warning until 11 AM EDT this morning for LSZ264-266-267.
Gale Warning until 8 AM EDT this morning for LSZ263.