Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 191916

Area Forecast Discussion
National Weather Service Marquette MI
316 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 through Monday)
Issued at 256 AM EDT TUE JUL 19 2016

Not much has changed in the last couple of days. Upper ridge
building overhead will promote hot and humid conditions and a few
shortwaves moving through or near the CWA Wed into Fri with a more
significant shortwave possible late in the work week or early
weekend. Sun and Mon is a toss-up on the pattern with the ECMWF
showing a deepening upper trough while the GFS has zonal flow or
slight ridging aloft. With a significant amount of uncertainty due
to convectively induced/altered shortwaves through Fri and vast
model disagreement/discontinuity later in the forecast period, stuck
with or close to the consensus guidance. Forecast confidence with
such shortwaves typically only increases within 12 hours of
occurrence. With ample instability, if convection can break the cap
it very easily could become strong to severe Wed through Fri.

Some details, where available/useful, are as follows.

A decaying convective cluster may move through on Wed, as shown by
the GFS, NAM, and to a similar degree the ECMWF. Will keep POPs
below likely given limited confidence. Of course, confidence in
temps is limited since the timing/extent of convection is uncertain.

Thu may see a convective complex dive through, as noted in the GFS
and NAM. If that does occur, temperatures would likely need to be
cut significantly.

After that the predictability is just too low to meaningfully
comment on.

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 206 PM EDT TUE JUL 19 2016

High pressure dominates into this evening, then a complex of
thunderstorms upstream with stronger upper level disturbance could
move over western Upper Michigan near daybreak on Wed. Only carrying
mention of vicinity showers at IWD and CMX until certainty increases
enough to include mention for thunderstorms. Overall VFR conditions
will prevail through the period.

.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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