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029
FXUS63 KAPX 221923
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
323 PM EDT Sat Jul 22 2017

.NEAR TERM...(Tonight through Sunday)
Issued at 323 PM EDT Sat Jul 22 2017

...Increasing chances of thunder Sunday...possibly severe...

High Impact Weather Potential...Marginal chance of severe storms
with a slight risk along and south of M-55.

Pattern Synopsis/Forecast...Low pressure continues to gradually make
it`s way eastward thru Northern Illinois toward Ohio late this
afternoon. Convection ahead of this system has consolidated into one
general area now impacting the Eastern Great Lakes and the Northern
Appalachian Mountains. Closer to home...scattered light showers
continue to develop across mainly northern and eastern portions of
our CWA along the backside of lingering low level moisture
associated with this departing system. A look upstream shows our
next area of vertically-stacked low pressure poised just north of
Minnesota attm...generating an area of convection just ahead of it
driven by strong upper level divergence and fueled by a modest
instability axis and 850 mb theta E ridge.

As we head into tonight and Sunday...this northern stream system
will drop SE into Lake Superior by 12Z Sunday...reaching the Straits
area by 00Z Monday. Upstream instability axis and 850 mb theta E
ridge just ahead of the stacked low will begin to slide into western
sections of our CWA by around 12Z Sunday...slowly making its way
eastward thru our area during the rest of the day and into the
evening hours. This timing coincides nicely with peak heating...and
the combined effort may produce a few strong/severe storms on
Sunday...especially during the afternoon/early evening hours. SPC
still shows almost all of our CWA within the marginal risk for
severe storms...with locations along and south of M-55 within the
slight risk for Sunday. Will increase thunder chances later tonight
across NW sections of our CWA as the instability axis approaches...
with thunder chances everywhere by Sunday afternoon.

Overnight lows will cool back into the low to mid 60s. Afternoon
highs on Sunday will range from the mid 60s in Eastern Upper
Michigan to the mid 70s across our southern CWA.

&&

.SHORT TERM...(Sunday night through Tuesday)
Issued at 323 PM EDT Sat Jul 22 2017

Showers are expected to diminish from west to east overnight Sunday
as the upper level wave clearly evident on water vapor imagery over
southern Manitoba slides southeastward across northern Michigan. Low
clouds will likely hang tough Monday morning but surface high
pressure then builds in leading to slowly clearing skies in the
afternoon from northwest to southeast (have slowed down the clearing
by a bit). In addition, a northwest flow aloft Monday will lead to
cooler temperatures. Rising heights in combination with a return
flow around departing high pressure will bring warmer temperatures
Tuesday. Lows Sunday night in the middle 50s to around 60. Highs
Monday in the lower and middle 70s. Undercut the blend a little
Monday night and went with lows ranging from the middle 40s to lower
50s due to radiational cooling. Warmer with highs in the upper 70s
to lower 80s Tuesday.

&&

.LONG TERM...(Tuesday night through Saturday)
Issued at 323 PM EDT Sat Jul 22 2017

Long range guidance continues to be in good agreement with the
extended period beginning with surface high pressure over the Great
Lakes region Tuesday. This high pressure will depart to the east as
a cold front associated with a low pressure system over James Bay
approaches from the west. Warm air advection showers will begin late
Tuesday night/early Wednesday morning with chances remaining through
Wednesday night/early Thursday morning with cold frontal passage and
lingering showers behind the departing front. High pressure then
builds back into the area behind the departing system, returning
partly cloudy skies and rain free weather for the weekend. Daytime
highs will be in the upper 70s to low 80s, while lows will drop down
into the mid to upper 50s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 103 PM EDT Sat Jul 22 2017

Cigs will gradually lower to MVFR over the next 24 hours as a
nearly vertically stacked area of low pressure slides into the
Northern Great Lakes region. Precip chances will increase... with
just a slight chance for a thunderstorm. Will leave any mention of
thunder out of the TAFs for now. East winds under 10 kts will
become light/variable tonight. Winds will begin to shift around to
the west around MBL and TVC by around midday Sunday as the low
moves thru the region.

&&

.MARINE...
Issued at 323 PM EDT Sat Jul 22 2017

Winds and waves will remain below SCA criteria through tonight...but
will possibly reach criteria by Sunday afternoon as easterly winds
strengthen ahead of the approaching low pressure system. Chances of
showers and storms will increase from NW to SE tonight and Sunday
ahead of low...with some stronger/severe storms possible Sunday
afternoon into early evening.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...NONE.
LS...NONE.
&&

$$

NEAR TERM...MR
SHORT TERM...AS
LONG TERM...TL
AVIATION...MR
MARINE...MR