NWS Forecast Discussion

FXUS63 KDTX 170330

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1130 PM EDT Mon Jul 16 2018


Strong synoptic scale cold front set to push through all of southeast
Michigan during the next couple of hours. Total air mass changeover
is set with 50 degree dewpoints now in FNT. System relative progs
show that subsidence is expected throughout almost the entire column
by early to mid morning Tuesday. Very high static stability will
limit boundary layer cloud growth. Expecting some patches of cumulus
to develop tied to recent rainfall, however, coverage is expected to
be very sparse. Northwest winds of 10 to 20 knots expected by
afternoon Tuesday.


* None


Issued at 253 PM EDT Mon Jul 16 2018


Big airmass change to take place tonight as strong upper level PV
anomaly/low over northern Ontario this afternoon drives a strong
cold front through southeast Michigan.

Hot and humid conditions around this afternoon as high temperatures
topped out around 90 degrees, with heat indices residing in the low
to mid 90s. 18Z SPC analysis shows MLCapes around 2000 J/Kg, but 0-6
KM bulk shear still under 30 knots. Good/numerous coverage of
activity developed and will taper off this evening as cold front
drives southeast. Bulk of activity across south half of the CWA tied
to 850-700 MB Theta-e moisture axis/pre-frontal trough, which is
already in the process of pulling east. Farther north, more of a
solid line of showers/thunderstorms with the actual cold front,
where a continued isolated marginal severe storm threat exists, as
the instability is embedded within the 30 knots of effective wind
shear. Enough updraft strength/cape values to support some hail as
well, despite high freezing levels (~15 kft)/wet bulb zero heights.
Activity will slide southeast and come to an end this evening as the
front clears the state by midnight.

Much drier and cooler air to follow for Tuesday-Wednesday, as PW
Values lower to around half an inch for the mid week period.
Favorable radiating conditions to allow mins to drop into the 50s
both Tuesday Night and Wednesday night, with even upper 40s likely
in the normally colder locations, which could set the stage for
patchy fog, mainly around the warm inland lakes.

Abundant sunshine tomorrow and 850 MB temps climbing back into 12-14
C range favors highs in the upper 70s to lower 80s, with
similar/perhaps slightly cooler temps for Wednesday with the cooler
start to the day.

Thursday will be the final day of dry, pleasant weather as surface
high pressure moves east of the region while shortwave ridging
traverses the region ahead of an approaching upper low. The upper
low is then progged to move into the region on Friday before
stalling over the region through the upcoming weekend. Increasing
moisture accompanying the upper low with PWATs in excess of 1.5
inches will support persistent shower and thunderstorm chances
Friday through Sunday. Temperatures will remain near average through
the extended period with highs in the upper 70s to lower 80s and
lows in the 60s.


Scattered to numerous thunderstorms through this evening as a cold
front tracks through the central Great Lakes. Modest southerly winds
through the daylight period, then turning northwesterly tonight
behind the front. Some increase in wind speeds will occur overnight
through Tuesday, but with gusts at 20 knots or less. Winds ease
Wednesday under building high pressure. This high will sustain
tranquil marine conditions through Thursdsay.


Numerous showers and thunderstorms will result in pockets of heavy
downpours through this evening. Due to the slow-moving nature of the
storms, localized amounts up to one inch will be possible. However,
basin average totals are forecast to remain near or below one half
of an inch.


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



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at www.weather.gov/detroit.

NWS DTX Office Area Forecast Discussion