NWS Forecast Discussion

FXUS63 KDTX 052303

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
703 PM EDT Wed Aug 5 2020


High pressure building over southern Lower Michigan tonight will
lead to mostly clear skies and calm to very light winds over the
next 24 hours. Another round of sct-bkn dirunal CU expected tomorrow
afternoon around 6000 feet.




Issued at 325 PM EDT Wed Aug 5 2020


Quiet weather continues today with large scale subsidence in the mid-
levels as high pressure remains firmly overhead. This broad surface
high slowly slides across the northern Ohio valley tonight
maintaining westerly winds over SE MI through this evening before
going light and variable overnight. Afternoon cloud cover will wane
with the loss of daytime heating after sunset giving way to a clear
or mostly clear night. This clearing will allow for significant
radiative cooling to occur allowing temps to drop back into the
lower 50`s, aside from the Metro area or along the lakeshores which
will see lows in the mid to upper 50`s.

Slight warming trend will continue the rest of this week as the
airmass undergoes modification. 850mb temps Thursday afternoon warm
to around 10-12C, compared to the 8-10C this afternoon, supporting
highs in the upper 70`s with the potential for a few spots to see
80. Similarly Friday 850mb temps reach 12-14C supporting low 80`s,
which are right around normal highs for this time of year.
Relatively clear skies at night will lead to a high amount of
radiational cooling keeping lows in the mid to upper 50`s Thursday
and Friday nights. A weak upper level shortwave moves across WI over
southern MI Thursday merging with another slightly stronger upper
level wave diving south out of Ontario across Lake Huron Friday.
There are slight discrepancies in the model suites with the
amplitude of said waves. The GFS/NAM suites show much more
amplification on both upper waves and try to generate a few isolated
light showers over SE MI Thursday into Friday. The
ECMWF/Canadian/UKMET suites are less amplified, especially on the
initial Thursday shortwave, keeping the region dry. Given the
stability of this airmass in the low to mid levels, it will be
difficult to generate rain with a lack of forcing so will keep dry
weather through the rest of the work week.

A hotter, more humid airmass begins to get fed into southern MI
Sunday and Monday. As mentioned in prior discussion, the divergences
in long range models still exist with the afternoon runs. Some
solutions point to a slower west-east progression of the surface low
and associated cold front with them not reaching SE MI until daytime
Monday. Others are a bit quicker reaching the area by daytime
Sunday. Plenty of moving parts at play with the how amplified the
upper trough will be as it moves across the Canadian Plains plus how
quickly it and the upper ridge over Quebec slide eastward. These
details will get ironed out as we get closer to the weekend. For
now, am keeping the chance PoPs and thunder in the forecast for the
beginning of next week.


High pressure centered near the Tri-State border will maintain mid-
level stability and dry conditions over the next several days.
Gradient winds look rather unimpressive through the near and short
term periods allowing for favorable boating conditions. An elevated
system will drop southeast into the central Great Lakes late
Saturday into Sunday brining the next chance for showers and
thunderstorms with a more cohesive southwest flow regime.


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



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NWS DTX Office Area Forecast Discussion