Area Forecast Discussion
Issued by NWS Gaylord, MI

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631
FXUS63 KAPX 180345
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1145 PM EDT Thu Aug 17 2017

.UPDATE...
Issued at 1000 PM EDT Thu Aug 17 2017

Deep low pressure has reached Upper Michigan late this evening.
Associated warm front is lifting NE out of our CWA attm...with the
cold front now moving toward Lake Michigan. Last vestiges of this
evening`s convection is moving off our Lake Huron shoreline as the
warm front exits. Convection behind this area is significantly
weaker and more spotty with no thunder in sight as the instability
axis exits as well. Rest of the night will feature mainly cloudy
skies with scattered showers and no thunder chances as low level CAA
commences with cold FROPA.

&&

.NEAR TERM...(Tonight through Friday)
Issued at 331 PM EDT Thu Aug 17 2017

...Showers/storms into the evening...

High Impact Weather Potential...A few thunderstorms remain
possible through early evening...marginal to slight risk for
severe storms.

Pattern Synopsis/Forecast...Deep well defined short wave/stacked
low has advanced into northern Wisconsin/western upper Michigan
this afternoon. Occluded/warm front arcs through Green Bay then
down through the SW part of the CWA where dewpoints have nudged
into the lower 70s...impressive for northern Michigan. Main
widespread batch of showers/embedded thunderstorms have pushed
north/east of the area at this juncture...while dry slot rotating
around the southern side of the low has punched into lower
Michigan.

With the juicy airmass and some heating...MLCAPE values have
increased to a modest 500+ J/KG and there are additional showers
that have popped across eastern Wisconsin/western lower Michigan
that will move through the region over the next several hours. But
by far...the better instability is well to our south into Ohio
where more vigorous thunderstorms are underway.

Primary Forecast Concerns...thunderstorm potential. Stacked low
will cross the upper peninsula later tonight and into Ontario on
Friday. Warm/occluding front slides through the region over the
next several hours along with narrow axis of instability
along/ahead of the front. But despite dewpoints pushing
70F...instability is not all that impressive owing to very slow
temp recovery today and a moist atmosphere/anemic lapse rates
aloft. Nonetheless...a few storms remain possible into early
evening. And with stronger winds aloft and backed low level flow/
some shear to work with...any storms could pose a threat.

Wrap around deeper moisture/low clouds/showers return later
tonight as upper low tracks through northern Michigan...and
persists into Friday. Looking like yet another cloudy/cooler
August day on tap for Friday with temps running nearly degrees
below normal.

&&

.SHORT TERM...(Friday night through Sunday)
Issued at 331 PM EDT Thu Aug 17 2017

...Generally pleasant weekend weather...

High Impact Weather Potential: Minimal.

Pattern Forecast: Low pressure plaguing the Great Lakes late this
week will gradually lift into western Quebec by Saturday morning.
Aside from a moisture-starved shortwave moving through the region
Friday night into Saturday morning, gradual mid-level height
rises/weak ridging and attendant surface high pressure will be the
dominant feature driving northern Michigan`s sensible weather
through the upcoming weekend.

Primary Forecast Concerns/Challenges: Any lingering lake induced
showers Friday night and PoPs Saturday as the bulk of shower/storm
activity passes by to our south.

Aside from a small chance for a few lingering northwest flow lake
induced showers Friday evening, precip chances continue to diminish
as deep layer moisture strips away to the northeast. By late Friday
night, a well-defined shortwave and attendant weak surface low over
northern IL continues to race eastward through southern MI/northern
IN and into northern OH by midday Saturday. Latest trends continue
to suggest that the vast majority of the CWA will remain dry as
showers/storm remain well to our south. Wouldn`t be shocked to see a
few sprinkles or a light shower, mainly in the far southeast portion
of the forecast area, but partly sunny skies and temperatures 5-10
degrees warmer than Friday will be the rule. Relatively weak
boundary layer flow should allow for lake breezes to develop...and
despite decreasing synoptic support/moisture Saturday afternoon
behind the departing trough axis, it`s not totally out of the realm
of possibilities that a rogue lake breeze induced shower or two pops
across sections of northeast Lower. Rather low confidence in that
thought precludes much more than slight chance PoPs at this point,
but something to monitor over the next 24-48 hours. High temps
Saturday right around normal... ranging from the mid-upper 70s.

Generally quiet weather is expected during the daylight hours Sunday
under mostly to partly sunny skies with temperatures warming another
5 or so degrees over Saturday. Highs above normal ranging from near
80 north to the low-mid 80s elsewhere.

.LONG TERM...(Sunday night through Thursday)
Issued at 331 PM EDT Thu Aug 17 2017

Height falls working into the region early in the week will bring
the best chance of widespread showers over the extended. Timing
continues to favor Tuesday for the arrival of widespread rain. Can`t
completely rule out some isolated showers Monday with a weak
boundary passing through and good return flow starting to increase
moisture as high pressure slides through the Ohio Valley Sunday.
Blends are still bringing at least partly cloudy skies for Monday,
which seems reasonable. Will have to see how strong and how long the
moisture advection affects the area prior to Monday. Temperatures
expected to run a bit above normal heading into midweek, with a
cooling trend later in the week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 1145 PM EDT Thu Aug 17 2017

Scattered showers will continue to impact all Northern Lower
Michigan TAF sites overnight thru much of Friday as deep low
pressure tracks eastward thru the Northern Great Lakes region.
Winds will shift to the W/NW overnight and strengthen to 15 to 25
kts on Friday.

&&

.MARINE...
Issued at 331 PM EDT Thu Aug 17 2017

Gusty southeasterly winds today will be replaced with gustier
westerly winds for Friday...as low pressure tracks through
northern Michigan into Ontario. Small craft advisories on all the
nearshore areas will likely be extended into Friday.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...BEACH HAZARDS STATEMENT through Friday evening for MIZ020-025-
     031.
     BEACH HAZARDS STATEMENT until 5 AM EDT Friday for MIZ008-015-017-
     018-024-030-036-042.
LH...SMALL CRAFT ADVISORY until 11 PM EDT Friday for LHZ345>349.
LM...SMALL CRAFT ADVISORY until 11 PM EDT Friday for LMZ323-341-342-
     344>346.
LS...SMALL CRAFT ADVISORY until 11 PM EDT Friday for LSZ321-322.
&&

$$

UPDATE...MR
NEAR TERM...BA
SHORT TERM...MG
LONG TERM...MK
AVIATION...MR
MARINE...BA



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