Area Forecast Discussion

FXUS63 KMQT 192251

Area Forecast Discussion
National Weather Service Marquette MI
651 PM EDT Fri Jul 19 2019

.SHORT TERM...(This evening through Saturday)
Issued at 307 PM EDT FRI JUL 19 2019

...Potentially Severe Thunderstorms Expected Tonight...

Clear skies this morning and afternoon are adding fuel to the fire 
in terms of convection this evening. GOES-E WV imagery  shows an 
area of mid level dry air between two masses of thunderstorms across 
MN and lower MI. The 12Z GRB, and to some extent 12Z INL, support 
this mid-level of dry air which will facilitate any severe wind 
threat this evening. The MCS across MN has diminished for the most 
part, with one stubborn cell continuing on. Cloud contamination has 
begun to find its way into western Upper Michigan in IWD from MCS 
across MN. Daytime highs and heat indices soared across much of 
Upper Michigan, with the temperature still climbing at the WFO. ISQ 
reached the mid 80s prior to the development of a Lake Michigan lake 
breeze. A light cu field as developed along Lake Michigan where the 
two lake breezes have converged. This area of convergence does have 
the potential to pop up a quick shower and thunderstorm or two this 

For tonight, CAMs are in agreement for a complex of thunderstorms 
developing to the west this evening. As a low pressure moves east 
into MN, models depict storm initialization around 19-21Z. These 
storms then appear to track east. Current model analysis shows a 
CAPE gradient running parallel along the WI border and then into 
Menominee and Delta counties. Some uncertainty exists on how far 
north the associated warm front and CAPE gradient extends into Upper 
Michigan which will play a major factor in how far north these 
storms make it into the UP. For now, have kept likely chances across 
the MI-WI border and then chances up into north-central UP tracking 
east towards the SOO. The atmosphere appears primed for convection 
as CAPE values reach up to 3000 J/kg depending on the model with 
bulk shear values 50-60 kts across much of the area. Hodographs show 
some clockwise turning in the lowest levels, but the majority of 
shear remains somewhat parallel to the boundary. If any isolated 
storm forms ahead of the line, all hazards appear likely with SRH 
values well over 300 to near 500m^2/s^2. Overall, storms appear to 
become cold pool dominated with all hazards remaining possible, with 
severe winds becoming most likely.

For tomorrow, as the jet and an area of PVA move through the area, 
light showers and thunderstorms are possible. It appears most will 
remain south into WI along the right-entrance region of the jet and 
surface boundary. Enough lift and moisture will remain in the area 
to leave mostly cloudy skies throughout Upper Michigan, however, 
temperatures and dewpoints will be much lower than today thanks to a 
frontal passage.

.LONG TERM...(Saturday night through Friday)
Issued at 313 PM EDT FRI JUL 19 2019

Models suggest that the quasi-zonal pattern across the northern 
CONUS will amplify from this weekend into next week as a ridge 
builds from the sw CONUS into Alberta/Saskatchewan and a downstream 
trough develops over the eastern half of Canada into the Great Lakes 
and eastern CONUS. The resulting nw flow on the backside of the 
trough axis through the northern Great Lakes will bring seasonably 
cooler and drier air into Upper Michigan this weekend into the 
early part of next week. 

Beginning Saturday night, any convection which may refire along the 
frontal boundary over southern MN and central WI on Saturday with 
the aid of a passing shortwave could clip the south central CWA on 
Sat. However, expect any remaining convection to generally slide 
south of Upper MI by 00Z Sun, with the possible exception of 
southern Menominee County. Will keep slight chance PoPs in fcst for 
the early evening for MNM to cover this remote possibility. Min 
temps should be more comfortable, generally in the 50s with falling 
dew points. Downsloping locations near the bay of Green Bay may only 
lower near 60F in light nw flow. 

Sun-Mon, dry weather will prevail as sfc high pressure builds 
eastward from the northern Plains. Comfortable July weather is 
expected with highs in the 70s and lows in the upper 40s to lower 
50s. Dew points will also drop into the upper 40s on Sunday and mid 
to upper 40s on Monday. 

Tue-Thu, expect increasing temps as the center of the sfc high 
settles more into the mid-MS and Ohio River Valleys and a westerly 
low level flow brings warmer air and slightly more moisture into the 
area. Any weak shortwaves in the nw mid/upper level flow could 
trigger some isold/sct shra/tsra by Wed/Thu. With limited coverage 
or upper level forcing, mainly dry conditions will still prevail 
through much of the week.

The pattern deamplifies for late next week with a transition again 
to quasi-zonal flow across the northern Great Lakes by Friday. Both 
the GFS and ECMWF indicate a shortwave and associated frontal 
boundary approaching from the northern Plains late in the day. This 
system could bring sct shra/tsra into the western half of the cwa by 
late Fri/Fri evening.

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 651 PM EDT FRI JUL 19 2019

Tricky forecast continues as it looks like an MCS will move along 
the WI border and our area will be on the northern periphery of it 
this evening. Looks like it would be showers so far with majority of 
the thunderstorms south. With this in mind, looks like VFR 
conditions will continue through the period at all sites. There 
could be some MVFR conditions briefly at SAW overnight. ALso, there 
could be some LLWS this evening briefly as well at SAW and IWD .

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 307 PM EDT FRI JUL 19 2019

Thunderstorms are possible on Lake Superior tonight, however most 
are expected to remain south. Patchy fog chances remain across Lake 
Superior until a cold front passed on Saturday. Winds will approach 
20 knots through this evening and a few gusts up to 25 knots for the 
higher platforms. Gusts up to 25 knots from the west to southwest 
are possible on Saturday, and then will remain below 20 knots 
through the rest of the forecast.

Upper Michigan...
Lake Superior...
Lake Michigan...