829
FXUS63 KDTX 081703
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
103 PM EDT Mon Jul 8 2024

.KEY MESSAGES...

- Isolated showers and thunderstorms will linger into Tuesday.

- Remnants of Beryl begin to impact Southeast Michigan Tuesday
  night and Wednesday with the potential for excessive rainfall.

- A prolonged period of above average temperatures is expected to
  start Friday and continue into early next week.

&&

.AVIATION...

A stationary front will remain draped across Southeast Michigan
through Tuesday. Isolated showers and thunderstorms will be possible
along this boundary throughout the forecast period. The greatest
likelihood for activity this afternoon and evening will be at MBS
and FNT. The focus for new development will shift south overnight
into Tuesday across the Detroit airspace. Coverage will be very
limited in time and space through midday Tuesday.

For DTW/D21 Convection...Thunderstorms are not expected across the
airspace this afternoon and evening. A very low potential exists
overnight through the daylight hours of Tuesday (peaking at a 20
percent chance - Tuesday midday).

DTW THRESHOLD PROBABILITIES...

* Low for ceilings at or below 5kft tonight and Tuesday.
* Low for thunderstorms overnight and Tuesday.

&&

.PREV DISCUSSION...
Issued at 307 AM EDT Mon Jul 8 2024

DISCUSSION...

As shortwave ridging over the area flattens and edges east today,
expect a weak frontal boundary to sag southeast into parts of the
forecast area. In advance of this front, temperatures will warm
nicely into the mid to upper 80s in many locations with a notable
increase in humidity as well as surface dew points climb into the
mid to upper 60s. This will yield modest instability with SBCAPE
readings around 1000 J/kg. Increasing west-southwesterly mid level
flow will also bring an increase in deep layer shear to 30 knots or
so by late in the day. So, scattered convection within area of low
level convergence along/near this front is expected with a strong
storm or two possible. Activity late this afternoon into evening
will focus over the Saginaw Valley into parts of the Thumb and will
be of the scattered variety.

This frontal boundary becomes very diffuse as it settles southeast
into the forecast area tonight into Tuesday as the mid level wave
driving it weakens considerably as it crosses the lower Great Lakes.
A bit of a sub-tropical air mass shifts into the area along this
stalled front with PWATs to near 1.75" by Tuesday morning along and
south of the mean frontal position (somewhere in the middle of the
forecast area). Periodic scattered showers/thundestorms will remain
possible, but with weak forcing and dubious instability within this
higher moisture environment, activity should remain disorganized
with only locally heavy downpours possible.

The attention turns to the remnants of Beryl late Tuesday night into
Wednesday and Wednesday night. 00z models have continued to converge
on a solution that will bring an extended period of rainfall, some
quite heavy, to the area. First, a significant surge of tropical air
will work into the region late Tuesday night into early Wednesday in
advance of this remnant low with PWATs increase to 2.00" or more.
This will promote an expanding area of rainfall into the region
which will lift from southwest to northeast across the area early
Wednesday. This will be followed by a shield of deformation rainfall
as what is left of the center of Beryl tracks through the northern
Ohio Valley to near western Lake Erie by Wednesday night. Additional
heavy rainfall will occur within this area closer to the core of the
system as PWATs remain on the order of 2.00".

At this time, it appears that the risk of a fairly wide swath of 2+
inches of rain looks increasingly likely over parts of the region
given the consensus track of Beryl this package. It will be very
interesting to see what the 12z model suite does as the system will
be better sampled as it is making landfall along the TX coast. If
this basic forecast track does not change too much, headlines to
highlight the flooding potential will most likely be required.

It should be noted that tropical systems often (but not always) have
some difficulty tracking this far north into the Great Lakes as they
re-curve around dominant ridging over the SE Conus and take a more
easterly trajectory once they encroach on this part of the country.
At this time, it appears that a northern stream shortwave dropping
fairly sharply southeast through the upper midwest will help steer
this system a bit farther north than usual as it helps re-establish
the lingering positive tilt trough positioned just west of the area
(hence a stronger consensus for heavy rain making it north into the
area). This northern system, now topping upper ridging over western
Canada, will also be better sampled today as it begins to translate
towards south central Canada. Today`s model solutions should give a
pretty decent indication of what will transpire with this system by
midweek.

Later this week into the weekend, general upper level troughing will
initially linger with temperatures in the 70s to around 80 slowly
building back into the 80s. By the weekend, this trough axis shifts
east with a more or less zonal upper level flow bringing very warm
temperatures back into the upper 80s to around 90. Rain chances may
linger into Thursday, but a fairly dry pattern seems to set up late
week into the weekend (although confidence by the weekend is pretty
low as an increasingly hot/humid air mass shifts back east into the
region.

MARINE...

Southerly wind around 10 to 15 knots today ushers in a warmer and
more unstable air mass ahead of a frontal boundary moving in from
the west. This system will bring a pattern of scattered showers and
storms mainly to Lake Huron today before coverage expands southward
to Lake St. Clair and Lake Erie tonight into Tuesday. Frontal
passage on Tuesday will veer wind to west/southwesterly with speed
remaining on the order of 10 knots or below. The mid-week period
remains a focus for more active weather as the remnant low pressure
of Beryl tracks northeast across the area. The forecast remains
sensitive to the eventual track and strength of the system, but
latest information continues to suggest gusty northeast winds and
heavy rain will be possible Wednesday into Thursday.

HYDROLOGY...

The remnants of Beryl will move into the area between a strong ridge
of high pressure over the southeast CONUS and a re-expanding upper
level wave positioned just to the west. This system will begin to
impact the Great Lakes Tuesday night into Wednesday with the remnant
low pressure center then tracking over/near the area Wednesday night
into early Thursday morning. At this time, the exact details on the
track of this system remain a bit tricky to determine. That said,
the risk for heavy rainfall still looks to be elevated as the system
encroaches on the area. Most of southeast Michigan is set to receive
at least an inch of rain, and if impacted directly, rainfall will
most likely reach or exceed 2 inches in some areas. If this scenario
unfolds, flooding will become a concern for Southeast Lower Michigan.

&&

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

$$

AVIATION.....Mann
DISCUSSION...DG
MARINE.......TF
HYDROLOGY....DG


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