579
FXUS63 KDTX 090705
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
305 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.

&&

.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.

&&

.PREV DISCUSSION...
Issued at 1050 PM EDT Wed May 8 2024

AVIATION...

VFR conditions hold through the night as mid-cloud lifts north from
OH/IN tied to developing low pressure over the Ohio Valley. Model
guidance has been trending further south with its track Thursday
shifting its precip coverage likewise further south. Detroit
terminals still have the greatest chances to see light, to perhaps
briefly, moderate showers Thursday afternoon with chances decreasing
further north you go. With lesser moisture advection in SE MI due to
this track, MVFR ceilings are more uncertain with low VFR being
favored in current forecast for the southern TAF sites. MBS has
increasing potential to remain completely dry so have taken out
precip mention with FNT reduced to a Prob30 group owing to the
decreasing confidence in precip extending that far north.

DTW THRESHOLD PROBABILITIES...

* Low for ceilings at or below 5000ft tonight into Thursday morning.
  High by Thursday afternoon.


&&

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

$$

DISCUSSION...SF
MARINE.......MV
AVIATION.....KDK


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at www.weather.gov/detroit.