National Weather Service - Area Forecast Discussion

FXUS63 KAPX 091052

Area Forecast Discussion
National Weather Service Gaylord MI
652 AM EDT Thu Jul 9 2020

Issued at 535 AM EDT Thu Jul 9 2020

For obvious reasons, pops have been drastically boosted and
expanded in eastern upper/nw and n central lower MI over the next
few hours. Line appears to be getting more raggedy very recently,
and still anticipate a considerable weakening trend at any time. But
this MCS has faked me out at least twice so far this morning.


.NEAR TERM...(Today through Tonight)
Issued at 402 AM EDT Thu Jul 9 2020

...Still hot with better chances for showers/storms...

High impact weather potential: Heat indices mid to upper 90s in
many areas. Thunderstorms at times, mainly non-severe.

Low pressure will move eastward across southern Canada, entering far
northern Ontario late tonight. An associated cold front will be
approaching the area by tomorrow morning. Southerly flow will be
developing ahead of the front, seemingly the first time in a while
that we`ve had a legit synoptic wind other than light/variable. That
southerly wind also brings in weak warm/moist advection at low
levels, as if we weren`t warm enough already. At 500mb, flat
shortwave ridging is overhead, but that is moving east. Sw mid-level
flow develops today and increases tonight, ahead of an upper trof
that reaches the mid/upper MS Valley. The above all adds up to
precip chances that, while still hit-or-miss, are higher than we`ve
seen in a while.

First off of course, we have a large mature MCS trying to move in
right now. An initial, smaller MCS has largely fallen apart as
tried to cross central upper MI. The 2nd, much larger and more
organized MCS is currently blasting across ne WI. This MCS has
been becoming outflow-dominant, with the leading bow echo setting
off less intense convective towers with time. But that weakening
process is still slower than expected. This MCS is coming to
northern MI to die, as most of them do. But clouds and precip
chances could well reach more of eastern upper and nw lower MI
than I originally planned. Expect some remnant convection to
reach at least western and central Mack/Chip Cos in eastern upper
MI this morning, and the Lake MI coastal counties of nw lower MI
as well. Anything more than that, well, we`ll see. This thing will
be running out of gas with time, moving in at exactly the wrong
time of day.

We will have enough cloud cover moving into eastern upper and nw
lower MI to at least slow our warm-up this morning. But that
cloud cover should also wipe out fairly quickly, and partly to
mostly sunny skies are expected by late morning. That will be
relatively brief; we have a somewhat more moist BL, and somewhat
cooler temps aloft behind the departing shortwave ridge. So cu
development will be faster and more vigorous than we have seen
over the last several days. Interior portions of northern lower MI
will transition to partly to even mostly cloudy. And deep moist
convection should follow, with uncapped MlCape values of 1000-
1250j/kg over northern lower MI this afternoon. We won`t have the
plethora of lake breeze boundaries to trigger things; low-level
winds are too strong for that. But an outflow boundary laid down
by the presently upstream MCS is inbound, and that should still be
around to help get things started.

Sct to numerous showers/storms are expected in northern lower MI
this afternoon, with the Lake MI coastal counties seeing less
coverage. Eastern upper MI appears less likely to get precip to fire
off there, but convection should initiate to the west, and work into
western Chip/Mack Cos as the afternoon proceeds. In northern lower
MI, instability is reasonable, but shear remains anemic (0-6km bulk
shear 15kt or less). Pulse strong storms are likely, and a stray
svr storm (hail/wind threat) is not impossible.

Max temps today will be 0f to 2f warmer that yesterday, ranging from
near 90f (eastern upper and far n central lower MI) to the mid 90s
(a good swath of ne lower MI). Dew points also tick upward by a
degree or so. Heat indices are in the mid to upper 90s across most
of northern MI, but don`t quite touch 100f. These are the hottest
heat indices of the warm spell thus far, and continue to warrant a
strong mention in the Haz Wx Outlook and social media outlets. It
doesn`t quite warrant a heat advisory, but we`re close. Came
closest to issuing for Arenac and Iosco Cos, in part to line up
with DTX, but ultimately our lack of urban areas compared to our
downstate neighbors was the decisive factor.

The forecast for tonight is mushy and not of terribly high
confidence. Clusters deep convection will develop in WI and western
upper MI this afternoon, with and ahead of the surface cold front,
and associated with falling heights aloft. These will start to work
across Lake MI and into eastern upper MI as soon as very late this
afternoon, but mainly this evening into overnight. CAMs are all over
the map as to how much success incoming convection will have in
getting here, though the RAP is trending in a direction that would
bring more convection across Lake MI. Bulk shear remains pretty
anemic, so we`ll have to see how potent of a cold pool upstream
convection can generate. But we could catch storms a smidgen earlier
in their life cycle tonight, as opposed to early this morning. A
marginal risk of SVR storms just scrapes Manistee/Benzie Cos again,
which seems reasonable. In addition, diurnal activity over northern
lower/eastern upper MI should be percolating deep into the evening
(at least). All told, a rather generic 40-50 pop is going to have to
suffice for now for tonight, until we get a better clue as to where
convective clusters initiate upstream.

Sticky min temps tonight in the mid 60s to lower 70s.


.SHORT TERM...(Friday through Saturday)
Issued at 402 AM EDT Thu Jul 9 2020

...Showers and Possible Storms with Abating Heat...

High Impact Weather Potential...Low.

Forecast Concerns...Pops Friday.

The upper level trough takes it`s time moving across the region
Friday so there is a decent chance for showers and possibly
thunderstorms through at least the morning and likely into the
afternoon as well (especially across eastern zones). Higher pressure
and associated drier air arrives Friday night and should hold into
Saturday. This is expected to lead to rain free and slightly cooler
but definitely less humid conditions. Temperatures are tricky Friday
as abundant clouds and showers would hold them down a bit while less
activity would push them higher. For now went with highs for both
days in the upper 70s to mid 80s. Lows Friday night in the upper 50s
to low 60s.

.LONG TERM...(Saturday night through Wednesday)
Issued at 402 AM EDT Thu Jul 9 2020

...More Comfortable Followed by Re-building Heat...

High Impact Weather Potential...Low.

A slow moving upper level trough will bring shower chances (and a
slight chance of thunderstorms) to the region Sunday. Extended
models then vary on the timing of when this system exits to the east
so chances for showers could linger into Monday as well (just slight
to low chance pops across northeast zones for now). Definitely
cooler than what we have seen here recently during this time with
highs in the mid 70s to low 80s. Upper level ridging and warmer
temperatures then return Tuesday with an approaching trough leading
to more precipitation chances Wednesday. Highs Tuesday in the mid to
upper 80s and Wednesday highs warming into the mid 80s to low 90s.


.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 652 AM EDT Thu Jul 9 2020

Shower and thunderstorm threats return this afternoon and tonight.

Line of TSRA inbound across Lake MI has rapidly fallen apart as it
moved into nw lower MI this morning. This line should completely
fall apart over the next couple of hours. However, it will get
plenty hot and humid this afternoon, and additional thunderstorm
development is expected. Most of these will be east of
MBL/TVC/PLN, with having the best chance of being impacted. Then
we wait and see if activity can take a run at us from WI this
evening and tonight. Mainly VFR, but brief restrictions are
possible in showers and TSRA.

Light southerly winds today.


Issued at 402 AM EDT Thu Jul 9 2020

Winds/waves expected to remain below headline criteria through the
balance of the week. However, southerly winds will be touch on
the breezy side in spots today. There will be periodic
thunderstorm chances on the lakes from now all the way through
Friday, that will bring special marine warning potential. Be sure
to monitor later forecasts/warnings.





NWS APX Office Area Forecast Discussion