Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 221347
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
947 AM EDT Sat Jul 22 2017

.UPDATE...
Issued at 947 AM EDT Sat Jul 22 2017

Low pressure is now centered over Iowa late this morning...with a
warm front extending eastward from the low just south of the Great
Lakes region. Several areas of convection continue to fire along
and north of the warm front...impacting mainly Illinois...
Indiana...Ohio and portions of Lower Michigan. Another low is
developing just NW of Minnesota just ahead of an unseasonably
strong closed upper low swinging SE out of South Central Canada.
This feature will be our next big rain maker for tonight and
Sunday. In the meantime...mainly light rain showers will remain
possibly thru the afternoon...along with an outside chance for an
isold thunderstorm. Temps will warm to afternoon highs in the
upper 70s and lower 80s despite mainly cloudy skies.

&&

.NEAR TERM...(Today through Tonight)
Issued at 334 AM EDT Sat Jul 22 2017

...Shower chances increasing again tonight...

High impact weather potential...stray, non-svr t-storms here and
there today and tonight. Locally heavy rain possible eastern upper
MI late tonight.

A skinny surface ridge is moving east of Lake Huron. Upstream, a
surface low is in eastern Neb/western Iowa, with a warm front
extending into central IL/IN, suppressed southward by MCS
activity. Further north, a weak surface low was along the ND/MN
border, with a quasi- warm front of its own extending into upper
MI. Deep convection presently extends from n central Iowa to
Toledo. Sct to nmrs light showers are occurring near/south of
M-72, along the far northern fringe of this activity. An earlier
MCS to our wnw has fallen apart, outside of some showers east of
the Keweenaw. Precip trends are the main concern.

Today...MCS remnants, and forcing associated with MCVs, will help
maintain some spotty showers this morning, primarily in the south.
In general the hi-res models have overstated precip this far north,
as activity to our south devours all the instability. Speaking of
which, any AM thunder threat looks to be fleeting at best, with
substantial instability staying south of I-96, and the ongoing MCS
to our south cutting off any attempt to bring this north. MCS
remnants will thin and/or exit as the morning

Will have plenty of cloud cover to start the day in most of northern
lower. Still, the mid/high debris clouds will thin with time,
allowing the sun to peek thru occasionally. (There will be
somewhat more in the way of sunshine in eastern upper MI this
morning.) Can we destabilize enough to pop some afternoon
convection? Temps will push to around 80f in spots, while dew
points remain in the sticky mid 60s. That helps build MlCape We
still have warmish temps aloft though, with 725mb temps of 9C
providing a cap that will take a bit of work to get past. With a
weak easterly synoptic breeze, lake breezes might provide a
sufficient trigger, but overall this is not an impressive setup
for convection. Hard to justify more than a 20 pop in parts of nw
lower, near Saginaw Bay, and in western portions of eastern upper
MI.

Max temps mainly upper 70s to around 80f, a touch cooler on the Lake
Huron coast.

Tonight...generally better precip chances tonight than today. Closed-
off 500mb wave now near Lake Winnipeg will move se-ward, and be
located near the Keweenaw by Sunday morning. Associated surface low
will advance toward eastern Superior and eastern upper MI. Shower
coverage will increase with time tonight, especially nw of a CAD-APN
line. Cooling temps aloft and associated steepening lapse rates will
keep MuCape values to increase some overnight, reaching 500j/kg in
parts of nw lower/eastern upper MI. So a thunder risk is certainly
in order, though a svr threat is not. However, this looks like a
sneakily-efficient rain producer, especially in eastern upper, as
overall moisture availability is high, and the system is relatively
slow-moving. Rainfall amounts could exceed an inch in portions of
eastern upper from late tonight into Sunday morning. Nowhere near
enough for flooding issues, but a potential good soaking.

Min temps near 60 to the mid 60s.

&&

.SHORT TERM...(Sunday through Monday)
Issued at 334 AM EDT Sat Jul 22 2017

High Impact Weather Potential...the possibility of severe weather
along and south of M-72 with a slight risk along and south of M-55.

Pattern Synopsis/Forecast...A potent 500 mb shortwave trough moves
down across Lake Superior and Lake Huron through the day. On the
southern side of the trough, is a 40 knot speed max on the GFS,
while the ECMWF has the jet max further downstate. The models have
that the best time for convection looks to be in the morning  as the
trough moves through E Upper. During the afternoon, the trough moves
east and drier air begins to squash the convection as well as the
CAA at the sfc and 850 mb. High pressure then begins to build into
the region overnight, so that the showers will be in NE Lower during
the evening, than move off overnight into Lake Huron. This sets up
for dry Monday as high pressure dominates for the next 24 hours
through Monday night.

Primary Forecast concerns...A little concerned with the timing of
the thunderstorm chances as any convection from Saturday night could
affect the amount that gets going Sunday morning. Also, sfc
temperatures begin to fall off, especially in the north, so that
rain will be likely, but chance for severe thunderstorms would
likely remain south of M-55, and probably US-10. Again the
confidence level of where convection and this boundary sets up is
low.

.LONG TERM...(Monday night through Friday)
Issued at 334 AM EDT Sat Jul 22 2017

...High pressure looks to dominate the next week...

High Impact Weather Potential...Elevated fire danger Tuesday and
thunderstorms Tuesday night into Wednesday.

Extended (Tuesday through Friday)...High pressure and dry air look
to dominate the region through the day 4-7 period with the Tuesday
afternoon looking to possibly having low Min RH, before the return
flow moves into the region ahead of the next cold front, which looks
to begin to move through the region Tuesday night. With this
happening along a cold front at night, there will be thunder
chances, but think that severe thunder is unlikely given how we
probably need better destabilization out ahead of the cold front. If
this timing on the models is to be believed, there could be issues
Wednesday south of M-72, but it will depend on how much we can heat
up before the front moves through by 00z. By WEdnesday night, the
next big high pressure moves into the region and remains through
Saturday. Temperatures look to be around normal (around 80F), so am
a little concerned that with the prolonged dryness that the Min RH
in the afternoons, especially for Friday and Saturday could drop to
sub 30%. Winds don`t look to be an issue, but warm temperatures and
low RH could elevate the fire danger going into the weekend. Won`t
put that into the HWO, but it is something to keep an eye on.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 643 AM EDT Sat Jul 22 2017

VFR today with some showers, especially early. MVFR cigs late
tonight.

A couple of areas of low pressure to our west will cross MI on
Sunday. Some sporadic rain chances will be seen today, especially
this morning. Showers will increase again from nw to se tonight,
especially overnight into nw lower MI. Lower cigs will accompany
the rain, and MVFR cigs are expected to develop at all taf sites
overnight.

Light east winds today, becoming variable tonight.

&&

.MARINE...
Issued at 334 AM EDT Sat Jul 22 2017

Light east to se winds will be seen into tonight, ahead of low
pressure systems in the central and northern plains. The northern
low will eventually cross northern MI on Sunday, with a light n to
ne breeze behind it by Sunday night. No advisories will be
necessary during this forecast.

&&

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

$$

UPDATE...MR
NEAR TERM...JZ
SHORT TERM...JL
LONG TERM...JL
AVIATION...JZ
MARINE...JZ



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