NWS Forecast Discussion

FXUS63 KDTX 152247

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
647 PM EDT Sat May 15 2021


A weak disturbance and associated moisture transport into the area
will bring lower cigs and sprinkles/scattered light showers. VFR
conditions will prevail for the most part, but periodic MVFR cigs or
vsbys cannot be ruled out. Ceilings hold into Sunday, but will lift
late in the forecast period. Light S/SW flow will back to SE Sunday.

For DTW...The potential for light showers in the 06z-10z window
still looks reasonable. The coverage will be scattered in nature and
cigs should remain above MVFR, but settle near 5 kft at times.


* Low for ceiling 5000 feet or less tonight and into Sunday morning.


Issued at 356 PM EDT Sat May 15 2021


The center of 1025 mb surface anticyclone is centered off of the
Atlantic seaboard this afternoon with a surface ridge axis extending
northwest through the central and northern Great Lakes. The surface
ridge will persist over Lower Michigan through at least Wednesday of
next week as stable lake aggregate forcing continues under the
anticyclonic shear side of a stationary upper level jet axis. Still
expecting predominately dry and very pleasant weather through the
middle of next week. Daytime temperatures will rise to temperatures top
out around 70 degrees once again, with min RH under 30 around 70 on
Sunday. A warming trend is then expecting Monday through Wednesday
as the warm air invades the state because of amplified ridge and
rising geopotential heights. Daytime highs are expected to make a
run at 80 degrees Tuesday and Wednesday with readings then reaching
the low to middle 80s Thursday and Friday.

A couple of low chance opportunities exist during the Tonight and
Sunday afternoon periods for some light rain activity. Deep upper
level cyclonic circulation over northern portions of Wisconsin will
direct a period of northward moisture transport directly across all
of Lower Michigan tonight and with remnants of deeper midlevel
saturation lagging over the state through the first half of Sunday.
Great structure to the warm advection moisture with some evidence of
at least transient leafing. Regional mosaic continues to show rain
upstream, but echoes dry out and fade as it tracks eastward. The
main limiting factor for precipitation continues to be the dry air
in place because of the surface ridging, surface dewpoints currently
running in the 20s to lower 30s. The dry surface dewpoints have
resulted in very high dry planetary boundary layer depths, in excess
of 8000 ft. Throw in upper level subsidence between 10.0 and 17.0
kft agl and work needs to be done to saturate. The mid/high cloud
will now remain in place this afternoon with what should be a good
amount of virga. Have maintained a low chance for light rain
beginning after 00Z this evening. It is certainly plausible that
nocturnal moisture transport/moistening aloft allows for some
activity overnight. Daytime heating will then allow for some light
shower development during the early afternoon hours Sunday. Model
data is less impressive with the midlevel lapse rates. Latest
forecast soundings suggest just a shallow layer of moist adiabatic
lapse rates between 6.5-10 kft agl. Given the very high LCL heights
it makes sense that models are now backing off on the amount of
moisture. The upper level jet axis is overhead so the potential for
unorganized shortwave advection to contribute to some synoptic lift.

Right entrance region dynamics will remain well south of Southeast
Michigan late Sunday and Monday. Latest trend is overwhelming in
keeping deformation/fgen forcing well south of Southeast Michigan.
That leaves the next chance at precipitation falling in the
Wednesday timeframe as large scale warm advection occurs with
meridional moisture transport within strong amplification to omega


Surface high pressure strung out over the central Appalachians
retains control of the lower atmosphere across the central Great
Lakes. Flow has been weak today with only minor upticks along some
shorelines resulting from lake breezes. Speeds trend even lower
tonight with further reduced pressure gradient. Negligible wind and
wave activity remains the story through most of the upcoming week as
speeds hold AOB 15 knots area-wide and directions oscillate between
southwesterly and southeasterly. Headline-free marine conditions
expected through at least Thursday.


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



You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.

NWS DTX Office Area Forecast Discussion