784
FXUS63 KDTX 010804
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
404 AM EDT Sat Jun 1 2024

.KEY MESSAGES...

- Dry weather for most of the day with rain moving in late this
  evening through Sunday morning. Rainfall totals generally range
  between 0.25" to 0.5".

- Warming trend through the weekend with drier conditions developing
  Sunday afternoon through Monday.

- Unsettled weather returns Tuesday and lasts through mid-week with
  periods of showers and thunderstorms possible.

&&

.DISCUSSION...

Pattern shift is underway this morning with GOES-16 infrared imagery
showing bands of cirrus spilling overhead in advance of a prominent
stream of Gulf moisture. Most of the daytime hours remain dry with
just thickening cloud cover, supporting a transition from filtered
sunshine to overcast skies by this afternoon. Daytime highs in the
mid to upper 70s settle right around normal for the first day of
June.

Radar mosaic shows a broad precipitation shield extending from a cut
off low in northern Missouri to the Gulf of Mexico, which will
slowly migrate and pivot north throughout the day as the low opens
and attempts to merge with longer wavelength troughing across
northern CONUS. The northward surge of this system draws a plume of
Gulf moisture into lower Michigan this evening, characterized by
forecast PWAT near 1.5" (90th percentile for this time of year) and
surface dewpoints above 60 degrees. Models still struggle to resolve
the northern and eastern extent of this moisture advection, however,
given the pervasive dry air that is currently in place (for
reference, current dewpoints are in the 40s). Other predictability
concerns arise with the amount of convection that is ongoing
upstream over the Mississippi Valley, which may further interrupt
northward moisture transport in addition to altering system
dynamics.

As the rain shield lifts toward southern Michigan, there will be a
degree of low level entrainment that may delay precipitation onset
until well after 00z (8 pm local) and/or evaporate portions of the
band itself. With this in mind, most areas will see between 0.25" to
0.5" of rain by Sunday morning with highest amounts west of I-75.
One area to monitor for overachievement potential is the Tri Cities,
where a decaying frontal zone/convergence axis and more reliable
moisture transport could lead to a locally enhanced rain band
although the bulk of model guidance keeps this feature northwest of
the cwa. Further south, deformation prospects will be tied to
low/mid-level closed circulations (925-700mb) that trail behind the
deep layer moisture, which will be cut off by a sharp mid-level dry
intrusion that follows immediately behind the wave. So while showers
may linger in these southern convergence zones, do not expect heavy
rainfall after 12z in these areas given the shrinking moisture
depths.

By Sunday afternoon, moisture will be confined to just a shallow
layer of diurnal cloud with clearing anticipated overnight. High
pressure briefly builds in for Monday alongside a warming trend.
Unsettled weather then develops for mid-week as we transition into
another closed upper low pattern, with energetic flow in both the
low and upper levels and thunderstorm chances as this transition
occurs.

&&

.MARINE...

Influence of high pressure wanes this morning as it drifts further
over the mid-Atlantic. Low pressure lifting into northern Ontario
drags a cold front into the Great Lakes with a secondary area of low
pressure developing along this boundary over the western Ohio Valley
today. Secondary low is set to track northeast into southern Great
Lakes this evening into the first half of Sunday bringing widespread
shower chances with a thunderstorm or two will be possible south of
Port Huron. Diffuse pressure gradient however results in generally
lighter winds (below 20kts) with this system. Weak high pressure
then briefly builds in late Sunday and Monday. Additional active
weather arrives midweek as a series of systems traverse the northern
CONUS.

&&

.HYDROLOGY...

Showers and possibly a stray thunderstorm move into SE Michigan this
evening as a deep supply of Gulf moisture converges with a weakening
cold front late this evening through Sunday morning. Rainfall
amounts expected to range between 0.25" to 0.5", although localized
higher amounts in excess of an inch are not out of the question
around the Tri Cities region. Minor flooding of urban and low-lying
areas, ponding of water on roadways, and rises in area rivers will be
the main impacts should an axis of heavy rainfall develop.

&&

.PREV DISCUSSION...
Issued at 1215 AM EDT Sat Jun 1 2024

AVIATION...

Expecting VFR conditions to prevail through this evening. High
clouds will be increasing throughout today in advance of a low
pressure system as winds hold out of the south to southeast at
around 10 knots or less. Rainfall expands across southeast Michigan
after 00Z this evening. It looks like VFR will largely prevail as
rain moves through, but any heavier showers may reduce
ceilings/vsbys toward borderline MVFR at times during the overnight
period. Increase in moisture will also bring possible MVFR ceilings
after 06Z early tomorrow morning.

For DTW/D21 Convection...Low chance for thunderstorms towards the
end of this TAF period. Weak instability upon the arrival of
precipitation should keep thunderstorm potential limited.

DTW THRESHOLD PROBABILITIES...

* Low for thunderstorms this evening and tonight

* Low or ceilings at or below 5,000 feet this evening.


&&

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

$$

DISCUSSION...MV
MARINE.......KDK
HYDROLOGY....MV
AVIATION.....AA


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