Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 150146
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
946 PM EDT Tue Aug 14 2018

.UPDATE...
Issued at 932 PM EDT Tue Aug 14 2018

Most of the radar returns have dissipated along frontal boundary
over upper Michigan this evening with loss of daytime heating.
Front will continue to sag slowly south overnight, reaching the
Tip of the Mitt by Wednesday morning. Likely just enough low level
moisture pooling and instability along the front to produce some
isolated shower activity overnight from parts of eastern upper
into the Tip of the Mitt - but most locations will be dry. A few
additional showers (thunderstorm?) may develop Wednesday morning
as the front moves south, although the most numerous activity
will come during the afternoon as the front encounters better
instability with daytime heating.

Very mild temperatures tonight, with many areas remaining in the
60s. Expect areas of fog to develop over parts of eastern upper
and interior northern lower after midnight.

UPDATE Issued at 724 PM EDT Tue Aug 14 2018

Pre-frontal convective showers/isold storms dissipating over
eastern upper with lowering sun angle and diminishing instability
early this evening. That trend should continue over the next
several hours. Upstream showers/storms over Wisconsin/western U.P.
may still impact the northern 1/2 of the area overnight - although
much of this activity will likely fall apart as it encounters
less favorable dynamics as it pushes east into our area. Because
of this, will lower POPs for many areas tonight. Will certainly
watch the upstream precipitation and will make adjustments this
evening if things hold together.

&&

.NEAR TERM...(Through Tonight)
Issued at 316 PM EDT Tue Aug 14 2018

...Warm and Muggy with some Convection Tonight...

High Impact Weather Potential: Minor, though a chance for
thunderstorms continues through Wednesday.

Primary Forecast Concerns/Challenges: Thunderstorm development and
any developing threats.

Pattern Synopsis/Forecast...Strong dynamics remain limited across
the forecast area this evening, as the storm system that was moving
over Ontario earlier today exits into Quebec. The cold front
associated with this system will slowly drop south into northern
Michigan this evening before stalling around Saginaw Bay through
Wednesday. 850/700mb qvectors show the best convergence this evening
focused right along the boundary over the Straits of Mackinac,
before slowly dropping south into Lower Michigan overnight.
Additional forcing overnight will be supplied at upper lvls, as the
right entrance region of a 70kt 300mb jet influences the northern
Great Lakes. Model soundings continue to show plenty of instabilty
for thunderstorm development over ern Upper this evening and
northern Lower overnight; with 0-3km MUcape diminishing to under
1200j/kg and 850/500mb lapse rates near 7c/km. Expect the main
threat with any thunderstorms tonight to be locally heavy rainfall
with freezing levels over 15k ft, pwats over 1 inch, sfc dew points
in the low 60s and 850mb dew pts around 14c. Expect the chance of
training thunderstorms (and heavy rainfall) tonight across Lower
Michigan as mid lvl winds remain light and frontal boundary stalls.
Also, some downdraft winds around 35kts can be expected with dcape
around 1000 j/kg.

Overall will continue with current forecast trends with convection
focused from the Straits north this evening, before becoming mainly
centered on Lower Michigan overnight.

&&

.SHORT TERM...(Wednesday through Friday)
Issued at 316 PM EDT Tue Aug 14 2018

High Impact Weather Potential: Chance for showers and isolated
storms Wednesday and Thursday.

A weak frontal boundary will be stalled out just north of Saginaw
Bay Wednesday. This keeps scattered shower and storm potential in
the forecast as moisture ahead of the next system interacts with the
front. The next system will be moving out of the mid-Mississippi
Valley toward southern Michigan through the day, and rain/storm
chances increase as this system approaches. PWATS in the Ohio Valley
increase to near 2.0" throughout the day with values of 1.0" to 1.5"
in nrn michigan. Cloud cover creeping north may limit daytime
instability a little, but there`s still a good chance of much of nrn
lower seeing scattered thunderstorms. CAPE values reach 1000 J/Kg,
and shear is weak (< 20 kts) so storms will be brief pulse-type.
Some stronger storms may form on lake breezes given the weak low
level winds. Shower and storm intensity drops off overnight, but
rain chances persist through to Thursday with moisture continuing to
increase over the area through the night. On Thursday the surface
low moving into southern Michigan may briefly try to draw the front
back northward as a warm front over our southern areas before the
surface low pulls off east. Overall rain and storm chances look good
again on Thursday especially in our south and and areas near Saginaw
Bay, given daytime instability and plenty of moisture around.
Temperatures Wednesday and Thursday will be a touch cooler than they
have been with highs in the upper 70s to low 80s.

.LONG TERM...(Friday night through Tuesday)
Issued at 316 PM EDT Tue Aug 14 2018

Friday into the weekend will dry out with weak subsidence and
shortwave ridging pushing into Michigan behind the departing system.
Surface high pressure may stick around for much of the weekend
before the next system approaches the area early next week. This
system has the potential to finally bring a good soaking rain to
much of the region, and will be worth watching. Temperatures through
the weekend into the beginning of next week stay mainly in the low
80s.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 724 PM EDT Tue Aug 14 2018

Weak frontal boundary working slowly into northern Michigan
overnight into the day on Wednesday. Clouds will increase from
north to south as the front approaches, although most areas will
remain VFR. A few showers possible tonight, with best chance of at
PLN. Areas of fog likely developing overnight and more fog may
need to added to the TAFs as things develop. This could create
areas of MVFR vsbys (something to watch).

Front sags through the area on Wednesday with scattered
showers and possibly a rumble of thunder. Not a widespread
precipitation event and will not include much precipitation in the
terminal forecasts.

Winds remaining light, shifting to the north/northwest after
fropa on Wednesday.


&&

.MARINE...
Issued at 316 PM EDT Tue Aug 14 2018

Winds and waves are expected to remain below small craft advisory
criteria through the forecast period, with mainly light southwest
winds this evening trending northwest Wednesday as a weakly
organized system passes through the northern Great Lakes. Some
thunderstorms are possible tonight over east Upper Michigan and
Straits of Mackinac, before thunderstorms drop south into Lower
Michigan Wednesday. Locally heavy rains and some wind gusts
are possible with these storms.


&&

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

$$

UPDATE...JK
NEAR TERM...SR
SHORT TERM...STJ
LONG TERM...STJ
AVIATION...JK
MARINE...SR


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