Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 192332

Area Forecast Discussion
National Weather Service Marquette MI
732 PM EDT TUE JUL 19 2016

.SHORT TERM...(This evening through Wednesday)
Issued at 314 PM EDT TUE JUL 19 2016

Upper ridge centered from southern Plains to south central Canada
shifts slightly east into Wed. At the sfc, high pressure over the
Great Lakes bringing quiet weather to the cwa late this aftn into
this evening will slide east while trough over the northern plains
slowly eases east. Warm front tied into trough over the plains will
stay southwest of Upper Michigan, keeping the extreme heat/humidity
over the northern Plains to the Mississippi River valley. Attn in
short term is on stronger shortwave currently in at least a couple
pieces moving into southern Manitoba and over central ND. May also be
an additional wave forming wnw of these two, though that really has
not taken shape yet.

Expect as this area of shortwave energy tops the ridge it will slide
across northern MN to northern WI and western Upper Michigan late
tonight toward daybreak on Wed. MUCAPE over 3000j/kg stays anchored
over northern plains beneath sharp ridge but gradient of MUCAPE will
be located from MN into Upper Michigan. h85-h3 thickness indicate
that if organzied shra/tsra top the ridge or redevelop later this
aftn/evening they would track over at least parts of Upper Michigan
into Wed morning. 0-1km shear over 20 kts indicates that complex
could maintain strength as it moves through. Overall there is a
least a small chance of severe storms - damaging winds would
probably be the primary hazard with a forward propagating MCS-moving
over parts of Upper Michigan late tonight into Wednesday morning.
Given there is already a well developed shortwave that will be
tracking across and persistent tsra, along with h85 convergence/warm
air advection that should be maintained thanks to that wave aloft,
does appear that chances of showers/storms moving through is
favorable. Not sure on the extent of severe weather though.

Additional shra/tsra on Wed a bit more uncertain. Does appear that
there is stronger subsidence/drying in the wake of the cluster of
shortwave energy currently topping the ridge aloft. This shows up as
large area of darkening on WV loop fm southern Saskatchewan sw
across MT so it is conceivable that after activity moves through in
the morning, the rest of the day may be more quiet. Could also see
outflow boundaries from the morning shra/tsra help to focus more
shra/tsra during peak heating in the aftn/evening hours. MLCAPEs
rise up over 1000j/kg in the aftn so if the focus for lift is there,
certainly could see stronger storms. At least now though it appears
larger scale lift from additional storms looks on the smallish side
and it may become overall more capped h8-h7 as the day progresses.
For pops/wx will ride with higher chances in the morning dropping
off to slight chances in the aftn. SPC has all the area in Margainal
risk on Wed. That seems reasonable with uncertainty on strength of
storms in the morning and questions about redevelopent in the aftn.

With the idea that shra/tsra will be less in the aftn, looks like it
could get hot mid-late aftn into early Wed evening. H85 temps top
out at least if 20c if not 21-22c. Soundings suggest mixing height
may be 50-75mb lower, but still should see max temps push toward the
90 degree mark or even low 90s over much of western cwa. Mid-upr 80s
elsewhere. Dwpnts rising well into the 60s seems reasonable based on
upsream readings today. Could see max apparent temps into the mid
90s over west cwa, as long as skies stay mostly sunny in the aftn.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 420 PM EDT TUE JUL 19 2016

The main issues for the extended forecast will be the well above
normal temperatures and humidity through the end of the work week.
Convection and cloud cover will likely end up keeping Thursday a bit
cooler than orignally expected; however, it will still be very warm
and muggy.

Wednesday night through Friday: The 500mb ridge axis is progged to
remain over the central part of the U.S., including the Great Lakes
region through this time period, with a short wave progged to ride
around the periphery of the ridge Wednesday night into Thursday
morning. The exact timing will largely depend on where the wave
develops and how quickly it progresses eastward and southeastward
into the area. The GFS has been consistent, over the past couple
days, with bringing the wave into the area by 12Z/21 and before
18Z/21 and now the NAM and EC have similar trends. The thunderstorms
associated with this complex would have the potential to be strong
to severe through early afternoon as MUCAPE values are progged to be
around 3000-4000 J/KG as the wave slides overhead. Additionally,
bulk shear values anywhere from 35 to 45 knots around the same time
frame. This would help to increase the potential for severe weather
across the area, provided the complex holds together. At this point,
SPC has the U.P. outlooked for a marginal risk of severe weather.
Temperatures will still be warm and humid for Thursday, but
temperatures are not expected to get as warm as initially thought if
convection lingers for a big portion of the day as it currently
appears. The GFS/EC/NAM have a cold front progged to slide southward
toward the CWA late Thursday afternoon and evening and to the south
of the U.P. by Friday morning as an associated stronger shortwave
slides across or just north of the area. Along and ahead of the cold
front, conditions may again become favorable for strong to severe
thunderstorms Thursday afternoon and evening as lift along the front
would help to overcome any capping that may be in place across the
area. Shear along the front is progged to be around 40 to 50 knots,
which would be more than enough to allow for strong to severe
thunderstorms. The shear also looks to be perpendicular to the
forcing which also supports more organized strong to severe
thunderstorm activity. The biggest limiting factor will be how long
cloud cover lingers after the initial wave slides through earlier in
the day Thursday. If cloud cover linger through the afternoon,
instability will likely be reduced. Behind the front, drier air will
filter in late Thursday night into Friday allowing skies to clear
and humidity values to pull back a bit. 850mb temps drop back to
around 18C, which would also keep high temps a little cooler for

Friday night through Sunday: The cold front that slid through the
area Thursday night is progged to slide back northward through the
CWA as a warm front late Friday night into Saturday morning. This
will be in response to a surface low progged to develop over the
Northern Plain into South-Central Canada. This will allow for
increased chances for showers and thunderstorms Saturday with warm
moist advection into the area. Saturday night through Sunday
morning, the low is progged to slide across Ontario while dragging a
cold front across the CWA. There continue to be timing issues with
the GFS being a little faster with the surface and upper level
features, while the EC slows the cold front down, allowing for a
Sunday afternoon passage. If the EC solution is correct the chances
for strong to severe thunderstorms would increase with peak heating,
but the GFS solution would bring the front through Sunday morning
with less instability.

Monday through the Extended: Models diverge during this time
period, as is typical at this range, with the GFS placing a ridge
across the area, while the EC lingers a trough across the Upper
Great Lakes. With the significant divergence between the models will
stick with a consensus for this time period.

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 732 PM EDT TUE JUL 19 2016

Although high pres is departing, vfr conditions will prevail at
KIWD/KCMX/KSAW thru this fcst period. As heat and moisture push back
into the area on s to sw winds behind the high, some shra/tsra could
arrive around or shortly after sunrise on Wed. Confidence is low as
is typically the case with convection. So, for now, have retained a
vcsh mention at KIWD/KCMX.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 314 PM EDT TUE JUL 19 2016

Winds will stay below 20 knots through the forecast period under
relatively a weak pressure gradient and high overwater stability.
Warm and humid air will flow across Lake Superior Wednesday through
Friday, which will allow fog to form, locally dense at times.

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


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