621
FXUS63 KDTX 091029
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
629 AM EDT Thu May 9 2024

.KEY MESSAGES...

- Much cooler today with increasing rain showers toward the southern
Michigan border.

- Greater coverage and higher rainfall amounts expected Saturday.

&&

.AVIATION...

An upper level short wave will track across the Ohio Valley today.
Southeast Michigan will remain on the northern side of the
associated rain shield, which should mainly impact locations from
FNT south across metro Detroit. While some light rain/sprinkles will
affect the area this morning. The better chances for more steady
light rain will be this afternoon into early evening. There will be
persistent ENE winds at roughly 8 to 14 knots today due to strong
high pressure centered north of the Great Lakes. This will sustain a
feed of low level dry air across Se Mi. The end result will be rain
that falls out of a high based cloud deck. Not only will clouds be
VFR based today, model soundings and probabolistic guidance suggests
cloud bases may only drop below 5000 ft periodically during the peak
of the rain late this afternoon and evening.

For DTW/D21 Convection...The instability will remain south and west
of the D21 airspace through the TAF period. So no thunderstorms are
forecast.

DTW THRESHOLD PROBABILITIES...

* Moderate in ceilings aob 5000 feet this afternoon and evening.

&&

.PREV DISCUSSION...
Issued at 305 AM EDT Thu May 9 2024

DISCUSSION...

Cold advection through the day today. The 00z APX raob indicated a 6
C temperature at 850 MB with a northeast wind. Low level northeast
winds will only increase and deepen (reaching 700 MB) through the
day, as 850 MB temps progged to reach 3-4 C over southeast Michigan,
which is still supportive of lower 60s. However, the cooler marine
layer off Lake Huron and thicker clouds and rain showers (south)
should lead to slightly cooler temps. The farther south trend
continued with the 00z NAM/regional GEM/RAP with the upper level
wave coming out of the Midwest. The corresponding 850 MB frontal
boundary now progged to reside over Central Indiana/Ohio with the
700 MB FGEN/shear axis not getting much past the southern Michigan
border. Will be going dry for M-46 northward, with pops then
increasing as one heads toward the southern Michigan border.

Positive tilted 500 MB trough axis to clear the State 9-12z Friday,
with short lived ridging building in during the daytime hours.
Still, the airmass starts out rather chilly (mins 40-45), 850 MB
temps around 1 C, and would not be shocked if isolated light showers
developed with the steepening diurnal low level lapse rates and some
modest cape (<100 J/kg) centered around freezing level. Ultimately,
will carry the silent 14 pop.

The next upper level wave is progged to move through far southern
Lower Michigan Saturday morning. This system is compact but robust
with the 500 MB low closing off at 547 DAM as the strong upper level
PV wraps around, and forcing looks to be maximized along and south
of M-59, as the 850-700 MB Theta-e ridge axis pivots and then sinks
south. Showers appear just about a done deal for southern two thirds
of the CWA, barring the system diving even farther south than
currently indicated. With the strong lift advertised over southern
areas and the showalter nearing zero, a slight chance of
thunderstorms also appears warranted. Conservative forecast for now
would indicated rainfall amounts near half an inch.

Good warm advection pattern kicks in for the end of the weekend, but
will have to be leery of the warm front activating and generating
showers and possible thunderstorms, best chance north of M-46. 850
MB temps reaching 10-12 C will allow for a warm Monday (70s), with
the timing and strength of a cold front being watched for potential
convection generation.

MARINE...

Low pressure tracks across the Ohio Valley today, with rain showers
flaring up along an elevated warm front through the morning. Shower
activity generally holds south of Harbor Beach. Easterly winds today
remain light which keeps wave heights aob 4 feet despite the onshore
component. Winds then veer to the northwest by early Friday morning
as high pressure attempts to build in from the north, leading to
drier conditions on Friday. This will be short-lived as the next low
pressure system traverses the broader troughing pattern aloft to
bring another round of rain chances for Saturday followed by high
pressure on Sunday.

&&

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

$$

AVIATION.....SC
DISCUSSION...SF
MARINE.......MV


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