804
FXUS63 KAPX 141919
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
319 PM EDT Wed Aug 14 2024

.KEY MESSAGES...

- Shower and thunderstorm chances Thursday night and Friday.
  Locally heavy rainfall possible, with non-zero chance at
  severe storms Friday afternoon.

- Another showery weekend

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 320 PM EDT Wed Aug 14 2024

Pattern/synopsis: High pressure over lower MI will move
eastward, to the eastern lakes and then approaching the mid-
Atlantic coast. Return flow will gradually increase behind the
high, ahead of a mature low and occluded front crossing the
upper MS Valley.

Forecast: Keeping an eye on some well-developed cu in eastern
upper MI, along the lake breeze convergence zone. Not expecting
to cook off up there, though. Quiet for tonight, though cloud
cover will start to increase from the sw. That increase continue
thru Thursday, with gradual moistening in increasing return
flow. Initially dry air will take some work to overcome, and
the main push of precip occurs Thu night and beyond. Filtered
sunshine will not result in any SbCape here on Thursday; we`re
too dry ahead of initial precip band. Some showers could work
into nw lower MI beginning toward midday. Pops increase thru the
afternoon and evening, again mainly nw lower MI. Marginal
elevated instability develops ne-ward across central Lake MI
late in the day. A chance for some thunderstorms emerges by
early evening, mainly west of TVC-CAD, with locally heavy rain
possible.

Lows tonight mid 50s to lower 60s. Highs Thursday upper 70s to
low-mid 80s.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Issued at 320 PM EDT Wed Aug 14 2024

Pattern Synopsis / Forecast: Frustratingly complex forecast in the
cards to close out the week. Slow moving 500mb shortwave and
associated surface low pressure / frontal boundaries will slowly
make their way through northern Michigan Thursday night through much
of the weekend. Moisture rich nature of this complex system will
lead to potential for heavy rain at times, particularly Thursday
night. A non-zero risk for severe storms may materialize Friday
afternoon as the cold front passes through near / during peak
heating. With moisture slow to erode on the backside of the system,
showers will continue to be possible Saturday and perhaps Sunday
too. High pressure briefly returns early next week before another
disturbance makes a run at the upper Great Lakes toward the middle
of next week.

WPC Excessive Rainfall Outlook: Day 2 (Thursday morning-Friday
morning) Marginal Risk- Focused across much of the CWA, with the
exception of areas east of an Oscoda to Paradise line. Day 3 (Friday
morning - Saturday morning) Marginal Risk- Focused primarily north /
east of the M-115 corridor.

Storm Prediction Center Severe Thunderstorm Outlook: Day 3 (Friday
morning-Saturday morning) Marginal Risk (Level 1/5) essentially
along and east of I-75 in both northern lower and eastern upper
Michigan.

Primary Forecast Concerns:

Heavy Rain Potential: Moisture advection will be in full swing as
the surface low and associated warm frontal boundary approaches.
Latest guidance is certainly remaining bullish on moisture
concentration, with PWATs as high as 1.5-1.8 (at or slightly above a
2 sigma anomaly for mid August) in the moisture pooling region along
the passing warm frontal boundary. Two distinct elements will be at
play with this rain: convective generation and synoptic generation.
Convective element will certainly be going strong across Wisconsin
through the day Thursday, but is expected to diminish somewhat as
the instability plume becomes stunted by loss of daytime heating
across northern Michigan. Some guidance tries to continue to force
some storms across NW lower, but wouldn`t anticipate this area
gutting much past I-75 and much farther north of M-72 Thursday
evening. Some of these storms could drop a quick 2.00"+ of rain,
which could certainly lead to some localized ponding of water, but
any convection should be transient enough to mitigate more serious
hydrological issues.

As the low continues its movement into the region, there are some
relatively strong signals for a synoptically forced area of steady
efficient rainfall Friday night into Saturday along the warm frontal
boundary, basically between M-72 and the Bridge. Excellent
divergence aloft from associated jet streak and an 850mb jet of 35-
45kts parallel to the front should provide ample lift along the warm
frontal boundary, generating the aforementioned area of enhanced
rainfall. There are some signals for some spots to see amounts in
excess of 2.00" of rainfall where this band of rain sets up...
though the longevity may mitigate a majority of flooding issues,
there will still be potential for low-lying / poor draining areas to
pond up during this outburst of rain Thursday night into Friday.

Friday Afternoon / Evening Severe Potential: As the low pressure
center works overhead and some daytime heating can materialize in
the dry slot, there will be potential for destabilization Friday
afternoon as the attendant surface cold frontal boundary makes its
way into the region. Some guidance is painting rapid destabilization
across northeast lower... in the event clearing can materialize.
Given the dynamics of the dry slot (steeper lapse rates, 0-6km shear
approaching 25-30kts), in the event convective temperatures (likely
anywhere from 76-80 degrees) can be realized, certainly enough there
to force a severe threat with primary hazards of damaging winds and
perhaps some hail too. This is highlighted by the Day 3 SPC outlook
putting NE lower and far eastern upper in a Marginal Risk. With all
that being said... wouldn`t be surprising to see a majority of this
activity hold south of the CWA (where better surface heating is
present) despite the expansive Day 3 outlook. More details to come
in the ensuing forecast cycles.

Rest of the weekend: Following the passage of the cold front,
continued cyclonic flow will allow for the prolonging of shower
activity into Saturday as moisture associated with the system is
slow to exit. Probably not a washout, but certainly a fitting day
for what has been a summer full of wet weekends. It does look like
the back half of the weekend will be drier, or at least have lesser
shower coverage. Given proximity of the system to the east, the best
/ longest lasting shower chances on Sunday would favor NE lower. We
eventually dry out Monday.

Temps: Humid with highs in the 70s Friday and Saturday, humidity
begins to ease Sunday and especially Monday with highs still in the
70s. Lows range from the 60s Thursday and Friday nights, eventually
into the 50s and 60s Saturday night, and low-to-mid 50s Monday night
and beyond.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 126 PM EDT Wed Aug 14 2024

Mostly VFR, though some fog possible MBL late tonight.

High pressure, centered over MI today, will slowly drift
eastward. Mainly clear skies into this evening. Clouds do start
to increase late tonight and Thursday. Still is a chance for
IFR fog at MBL late tonight, but do not have vsbys dropping as
low as they did this morning. Better precip chances arrive at
MBL/TVC just beyond this TAF period.

Light winds into tonight. Southerly breezes increase on
Thursday.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.

&&

$$

SHORT TERM...JZ
LONG TERM...HAD
AVIATION...JZ