National Weather Service United States Department of Commerce


000
FXUS63 KDTX 050959
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
559 AM EDT Sun Apr 5 2020


.AVIATION...

High pressure building in behind a passing cold front has created an
inversion trapping low level moisture and resulting in widespread
MVFR stratus around 1200ft. As the drier low level air continues to
stream into SE MI, the stratus will scatter out from NW to SE this
morning. MBS has already broken out of the stratus and the dry air
should reach FNT around 12Z. As the low level clouds scour out this
morning, a mid cloud deck around 10kft will pass overhead. Skies
look to clear out this afternoon for all sites after 21Z. Winds will
be at or below 10 knots from the north this morning with a
decreasing trend through the day as it slowly veers more
northeasterly.

For DTW...MVFR stratus will hold for a couple hours before scouring
out around 14Z this morning. VFR skies will then prevail through the
remainder of the forecast with only a few hours of clouds
around 10kft today before going clear after 21Z.

DTW THRESHOLD PROBABILITIES...

* High for cigs at or below 5000 ft through 14Z. Low after 14Z.

&&

.PREV DISCUSSION...
Issued at 349 AM EDT Sun Apr 5 2020

DISCUSSION...

Shallow cold air advection across the lowest 2000 ft ongoing early
this morning, as the governing cold frontal boundary slowly eases
through the area. Boundary layer drying captured via recent
satellite trends by the defined clearing working through central
lower MI will take a good portion of the morning period to
definitively penetrate southeast sections of the state. This will
leave some lingering areas of stratus early, before the combination
of steady drying and diurnal mixing offers greater clearing
potential as high clouds thin with time heading into the afternoon.
Higher prospects for full late day insolation works to offset this
modestly cooler resident thermal profile, supporting highs of lower
to middle 50s for inland locations. A gradually veering low level
flow in response to encroaching high pressure will establish a
prevailing flow off the colder lake Huron waters. This will mute the
response for locations immediately downstream (thumb region, Bay
county), with readings holding in the low to mid 40s. High pressure
anchored over the region then offers favorable radiational cooling
conditions under clear skies and light winds tonight. Lows bottoming
out in the mid to upper 20s in many spots.

A dry and stable profile as high pressure only slowly relinquishes
control ensures quiet conditions with plenty of sunshine Monday.
Simply general airmass modification as warm air advection across the
lowest 925 mb remains limited thanks to prevailing southeast flow.
This will still net a solid warming trend off readings noted today -
highs upper 50s except near the colder waterways.

A weak baroclinic zone will emerge within the existing lower
amplitude westerly flow during the early week period. This boundary
will edge northward with time as a warm front in response to
increasing warm air advection upstream. Shortwave energy working
through the mean flow will subsequently look to engage the
underlying moist isentropic ascent, offering two main windows for
possible precipitation development Monday night through Tuesday
night. Placement of both the better moisture quality and forcing
toward the south maintains greater potential generally south of M-59
for the first window Monday night/early Tuesday. A greater northward
surge of theta-e by Tuesday evening will introduce the possibility
of elevated thunder within a more expansive precip shield. Close
proximity of the near surface warm front also points to a
substantial component of low cloud and the possibility of fog during
this time, particularly should the boundary remain just to the
south/west. This yields a more challenging high temp forecast Tuesday
- the milder resident environment perhaps tempered by restricted
insolation potential and possible precip.

Above average warmth holds for one final day Wednesday, the thermal
profile responding to a brief window of late day warm air advection
in advance of a pending strong cold frontal passage. Assuming a high
degree of insolation, outgoing forecast continues to support
afternoon readings well into the 60s. Solid shot for precipitation
Wed night given strong frontal convergence and inbound height falls,
but with no real signal of meaningful instability to support a
thunder mention at this stage. Cold and windy post-frontal
conditions Thursday, with established high amplitude trough
reinforcing this colder resident environment right into next
weekend.

MARINE...

Marine stratus beneath a strong subsidence inversion will gradually
erode this morning as high pressure strengthens over Lake Michigan
delivering drier northwest flow. Persistent weak surface pressure
gradient will keep prevailing winds in the 10-15 knot range with
only a few more hours of 20 knot gusts along the northern
international border owing to compressed residual 925 mb heights.
Ample dry air aloft will remain as the high slowly shifts east into
Lake Erie on Monday as the anticyclonic circulation breaks down.
Inbound low pressure late Monday will shift winds southeasterly with
increasing humidity. Expect periods of rain and thunder, especially
Tuesday afternoon/evening. Wind and wave response will be limited.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&

$$

AVIATION.....DRK
DISCUSSION...MR
MARINE.......KK


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