Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 210707

Area Forecast Discussion
National Weather Service Gaylord MI
307 AM EDT THU JUL 21 2016

.SHORT TERM...(Today and tonight)
Issued at 307 AM EDT Thu Jul 21 2016

High pressure center has reached the Mid Atlantic states early this
morning...while low pressure remains over the Northern Plains.
Southerly flow between these two systems continues to pull very warm
and increasingly humid air into the Western Great Lakes region.
Mainly clear skies and dry weather continue across all of Michigan
attm. All focus for upstream convection remains along and just ahead
of the cold front currently over Northern Minnesota and Eastern
North Dakota where strong instability (MUCAPES of around 5000
J/kg)...pronounced 850 mb theta e ridging and 0-3 km bulk shear of
35 to 40 kts all reside.

Cold front will lean into Northern Michigan by this
will the instability axis and the 850 mb theta e ridge. MUCAPES will
increase to near 4000 J/kg this afternoon and evening as high temps
soar into the mid 80s to lower 90s and dwpts push into the lower
70s. In addition...0-3 km bulk shear values will rise to around 40
kts across our entire CWA during peak heating/instability...with
descent directional shear as well. Thus...still expect chances of
showers and thunderstorms will steadily increase from NW to SE
across our entire CWA today...with the best chance developing during
the afternoon and evening. There certainly remains a chance for
severe storms given the all of above parameters coming together
during max diurnal instability...matching well with SPC slight risk
over much of Michigan. Strong/damaging winds and large hail are
possible with any severe storms...along with torrential rain. Given
the expectation of strong shear values (both speed and direction)...
isolated tornadoes are also not out of the question.

Still expect an overall diminish in both areal coverage and
intensity of ongoing convection overnight with loss of diurnal
component and as the cold front itself begins to wash out.

.LONG TERM...(Friday through Wednesday)
Issued at 307 AM EDT Thu Jul 21 2016

...More thunderstorms Saturday night into Sunday...

Ridging at the surface and aloft for Friday looks like it will hold
on into Saturday as well. This will bring a stretch of hot but
slightly less humid condtions. A northern stream trough and
associated surface cold front will then lead to increasing humidity
along with chances for showers and thunderstorms late Saturday night
and especially on Sunday. High pressure then builds back in early
next week leading to seasonable temperatures and lower humidity.
The main forecast concerns revolve around temperatures and pops
through the period.

Friday...Any showers and storms should be well east of the region
with decreasing clouds and slightly less humidity. Another hot day
with highs ranging from the middle 80s north to the middle 90s

Friday night into Saturday...Not a lot expected to go on with high
pressure remaining in control. Humidity will once again be on the
increase Saturday afternoon as we get into a more moist return flow
around departing high pressure. Lows in the middle to upper 60s.
Highs in the middle 80s to lower 90s.

Saturday night into Sunday...Low pressure tracks across southern
Canada and drags a surface cold front across the region. Humidity
increases once again with some instability developing out ahead of
this system. This will lead to increasing chances for showers and
thunderstorms. Lows in the muggy middle to upper 60s and highs
ranging from the upper 70s to middle 80s.

Monday through Wednesday...Upper troughing dips down into the region
bringing small chances for a few showers across northern zones
Monday. High pressure then rebuilds back in bringing a break in the
action for Tuesday which likely holds into Wednesday. Temperatures
should be near seasonable levels with humidity levels in the
moderate range.


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1147 PM EDT Wed Jul 20 2016

Evolution of showers/storms over the next one to two days is the
main forecast problem.

High pressure over the mid Atlantic coast will remain in control
of northern Michigans weather through the rest of tonight, with
solid VFR conditions persisting. Upstream, lots of warm/unstable
stretches up through the plains to subtle surface low pressure in
the Dakotas. Line of thunderstorms are now developing in that
region and up into Canada. Some of that activity may spread into
northern Michigan tomorrow morning through midday. Additional
thunderstorm development is possible Thursday afternoon and into
the evening, but will depend on how things evolve. Right now, best
chances at the terminal sites for shra/tsra appear to be through
the afternoon hours. Otherwise, conditions will remain VFR.


Issued at 307 AM EDT Thu Jul 21 2016

SW low level flow will strengthen today ahead of a cold front
leaning into Michigan. Winds and waves will reach SCA criteria today
across most of our nearshore areas...and will remain within criteria
tonight for most of our Northern Lake Michigan nearshore areas as
winds shift to the west behind the cold front. Chances of showers
and thunderstorms will also increase today and tonight...with the
best chance for convection during the afternoon and evening during
peak instability. There is also a chance for severe storms during
this time thanks to strong instability...high dwpt air and the
development of both speed and directional wind shear.


.APX Watches/Warnings/Advisories...
LH...SMALL CRAFT ADVISORY from 8 AM this morning to 8 PM EDT this
     evening for LHZ345>347.

LM...SMALL CRAFT ADVISORY from 8 AM this morning to 8 PM EDT this
     evening for LMZ341.

     SMALL CRAFT ADVISORY from 8 AM this morning to 8 AM EDT Friday
     for LMZ323-342-344>346.

LS...SMALL CRAFT ADVISORY from 8 AM this morning to 8 PM EDT this
     evening for LSZ321-322.



LONG TERM...Sullivan
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