NWS Forecast Discussion

FXUS63 KDTX 121946

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
346 PM EDT Wed Aug 12 2020


Persistence forecast in play today with the influence of high
pressure and antecedent dry conditions (PW values between .60 and
.75 inches) producing another round of mostly sunny skies.
Temperatures have warmed up nicely in the mid 80s, and will again
fall back into the upper 50s to lower 60s overnight given the clear
skies and efficient radiational cooling. This theme of mainly sunny
conditions with temperatures in the mid to upper 80s will continue
through at least Friday as a northwest Pacific wave crashes onshore,
which will amplify ridging across the Midwest and will promote
subsidence aloft. Wind speeds will remain light but will turn more
ENE to E Thursday into Friday, which will result in slightly cooler
temperatures along the Lake Huron shoreline.

Some models continue to diverge regarding precipitation chances
Saturday tied to the potential evolution and strengthening of a wave
over KY/TN that could pivot northeast into the Ohio Valley ahead of
an approaching upper-level trough. Deterministic 12Z GFS and Canadian
run favor this scenario and draws the wave north some time between
Saturday afternoon and evening, producing overcast skies and rain
showers. 12Z ECMWF model run (and prior 00Z run) holds the wave south
across TN as it gradually weakens and travels east into the
Carolinas, favoring a dry solution. Diving into the 00Z ensembles,
the GEFS solutions are extremely bullish with the rain scenario where
nearly 85% of members exhibit a similar 500 mb pattern to the
deterministic run, however, the EPS and Canadian ensembles mirror the
dry solution. Overall, will keep the chance PoPs and will favor the
dry solution until additional convergence is exhibited for Saturday.
Will then also hold temperatures in the low to mid-80s for Saturday
high given a hedge towards a drier solution, but it is worth noting
that any rain showers would easily knock daytime highs down ~4-6

Otherwise, higher confidence exists regarding upper-level trough and
associated surface front dropping across the Great Lakes some time
between Sunday and Monday which will bring better chances for
showers and thunderstorms along with cooler temperature trends
following the passage of the front. Ensemble guidance also points
towards a second high pressure system filling in behind the front
which would bring another period of dry conditions through the
middle of next week.



Dry conditions persist across the central Great Lakes as high
pressure continues to build overhead. Light and variable winds will
gradually back to the northeast, with winds increasing to 10 to 15
knots by midday Thursday. Gusts could reach around 20 knots Thursday
afternoon/evening, particularly across Saginaw Bay due to its
northeasterly fetch. Overall boating conditions are expected to
remain favorable through the end of the week before another
potential system approaches the central Great Lakes this weekend.


Issued at 120 PM EDT Wed Aug 12 2020


High pressure firmly over lower Michigan with dry air in the low and
mid-levels will help to suppress diurnal cloud formation this
afternoon/evening. Bands of cirrus originating from the stalled
frontal boundary over the Ohio valley will continue to stream in
over the southern TAFs through the evening. Clearing will occur in
the late evening leading to a clear or mostly clear night. Winds
will remain light and variable to light easterly through the night.


* None


Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.



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NWS DTX Office Area Forecast Discussion