Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 150650
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
250 AM EDT Sat Jul 15 2017

.SHORT TERM...(This evening through Saturday)
Issued at 225 PM EDT FRI JUL 14 2017

As the main upper-level trough axis continued to push south east of
the area, surface high pressure dropped southeast across Minnesota
this afternoon. This allowed skies to finally clear across a good
portion of the area and the return of drier weather across Upper
Michigan. The main forecast concerns through Saturday will be the
arrival of a trailing cold front and the possibility of strong to
severe storms Saturday afternoon and evening along the
Wisconsin/Michigan border and into south central portions of Upper
Michigan.

Tonight clear skies and mostly light winds will allow for a
seasonably cool night. There could be a few areas of patchy ground
fog given the recently moist conditions, but with how dry the low to
mid levels are overall, expect any fog that can develop to be very
shallow with minimal impacts. The attention then turns towards early
Saturday morning as a few elevated thunderstorms look possible ahead
of the advancing cold front across western Lake Superior and
possibly across the Keweenaw Peninsula as 900-700mb moisture
transport and a weak PV anomaly push east across the area. Overall,
models are in fairly good agreement with any lingering convection
waning.

Through the late morning and early afternoon hours, the surface cold
front is progged to push east across the area into central portions
of Upper Michigan. This is still some uncertainty in regards to
where convection will initiate in the afternoon hours, but the
overall consensus is for scattered storms to develop across central
portions of Upper Michigan in the mid-afternoon hours as the nose of
better instability pushes into the area. Right now there is also
quite a spread among the models in regards to the degree of
instability, with the GFS being by far the most bullish, and rather
unrealistic, with 4500+ J/kg of MUCAPE. The NAM and Canadian look a
bit high as well with upwards of 2500-3000 J/kg of MUCAPE, but not
totally unrealistic, especially if some of the better low-level
moisture can rotate around the surface ridge ahead of the advancing
cold front. With around 30 knots of effective bulk shear oriented
quasi-perpendicular to the surface front, storms should be able to
maintain strong and possibly even severe levels as they push
southeast across the south central through the late afternoon and
evening hours. Hail will be a threat from convection that does
develop as steeper mid-level lapse rates will move into the area
along the cold front. Instability profiles look rather fat,
especially through the hail growth region; however, wet-bulb zero
heights may be a bit too high to develop severe hail in any storms
that do not rotate. Strong downburst winds will also be a threat,
especially with stronger updrafts as a moderate amount of DCAPE is
progged to be in placed with strengthening 0-3km shear and
steepening low-level lapse rates.

.LONG TERM...(Saturday night through Friday)
Issued at 239 PM EDT FRI JUL 14 2017

Upper air pattern consists of a 500 mb ridge in the Rockies and
northern plains 00z Sun with a trough across the ern U.S. and in the
Pacific NW. The ridge moves east into the upper Great Lakes on Mon.
Convection will move out Sat evening and then will be quiet into Mon
for weather. Overall, did not make too many changes to the going
forecast.

In the extended, GFS and ECMWF show a 500 mb ridge across the
southern U.S. with a broad trough across central Canada 12z Tue.
There is a shortwave over the upper Great Lakes then and a sfc cold
front that will move through the cwa on Tue. The ridge remains
through 12z Wed with the area having zonal flow. The upper Great
Lakes remains in the ring of fire scenario through this extended
period with the sfc front moving south and stalling out along with
it slowly dissipating. Boundary between warm and humid conditions
and cooler air will be mainly just to the south of the area.
&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 249 AM EDT SAT JUL 15 2017

VFR conditions will prevail at KIWD/KCMX/KSAW thru this aftn though
there may be some shallow ground fog at times at KIWD for the next
few hrs. A cold front dropping se across the area today may spark a
few shra/tstms, but confidence in coverage and location of
development is low. Right now, it appears central Upper MI has a
better potential of seeing sct pcpn development than western Upper
MI. Have thus included a VCSH mention during the mid/late aftn at
KSAW. Passage of cold front and development of cool upslope flow may
result in low MVFR or IFR cigs for a time this evening, especially
at KSAW.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 225 PM EDT FRI JUL 14 2017

Ahead of an advancing cold front, winds will increase to 15 to 20
knots across the western and northern half of Lake Superior tonight
and through Saturday morning. Further to the east during the same
time period, winds will be 10 to 15 knots. As the front pushes south
of the area, winds will become north-northeasterly Saturday evening
into Sunday around 15 to 20 knots. Sunday afternoon winds will
weaken to around 10 to 15 knots. Next week we could see a day or two
with wind speeds up to 15 to 20 knots, otherwise winds will remain
around or less than 15 knots.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...Ritzman
LONG TERM...07
AVIATION...Beachler
MARINE...Ritzman



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