000
FXUS63 KDTX 200001
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
801 PM EDT Fri Apr 19 2024

.KEY MESSAGES...

- Cool and quiet weather this weekend. Frost is possible Saturday
night and Sunday night.

- Next chance of showers and thunderstorms arrives Tuesday.

&&

.AVIATION...

VFR conditions will prevail through this TAF period. Thicker mid
clouds are streaming into KMBS at around 6kft this evening. Expect
these clouds to spread across terminals tonight with more FEW to SCT
coverage across southern terminals. Gusty west winds are expected to
decrease by around 02Z, but sustained winds to around 10 knots will
hold through tonight. Greater cold air and associated steep low level
lapse rates will support a healthy diurnal cumulus response by late
tomorrow morning with a BKN VFR deck around 5-6kft developing. Winds
again will be out of the west and gusting to around 25 knots.

DTW THRESHOLD PROBABILITIES...

* None

&&

.PREV DISCUSSION...
Issued at 306 PM EDT Fri Apr 19 2024

DISCUSSION...

Mid level subsidence has fostered a period of respectable post
frontal drying which has led to a sunny albeit cool afternoon across
Se Mi. A region of high based clouds now over IL/IN will lift
northeast across potions of Se Mi this evening. These are the result
of some weak mid level isentropic ascent within the entrance region
of a mid level jet streak. A decrease in the clouds overnight and a
very dry boundary layer will support enough radiational cooling to
drop overnight temps into the 30s. A mid level short wave trough
axis now over the Dakotas and Minnesota will rotate across Se Mi
during the morning on Saturday. Despite the mid level height falls
and differential vorticity advection, the column will remain very
dry and not supportive of precip. The passage of this wave will
drive colder air into Se Mi (850mb temps of -6 to -8c) by afternoon.
Model soundings also indicate steep low level lapse rates with
enough moisture to support a healthy cu field during the afternoon.
This will keep afternoon temps in the mid 40s to near 50. With 20 to
25 knot westerly winds in the mixed layer, it will be a rather brisk
spring day. The gradient flow will persist through Sat night. Given
the degree of cold air, Sat night mins still are forecast to drop
into the low to mid 30s.

A polar low is forecast to slide across James Bay into northern
Quebec Sunday into Monday. Lower Mi will be within the mid level
confluence between this feature and an upstream ridge. This will
sustain broad large scale subsidence and dry conditions across the
region. The upper low is forecast to a drive a shallow cold front
across Lake Huron Sunday afternoon/evening. This front will likely
weaken Sun night before lifting north as a warm front on Monday as
developing southwest flow begins to drive slightly warmer air across
Lower Mi.

Forecast amplification of a mid level wave emerging from the northern
Rockies and traversing the Great Lakes Tues/Tues night will support
the next chance for rain. Moisture transport into this system along
with good large scale ascent will support a 60-70 percent of
showers. Weak elevated instability will also warrant a chance for a
thunderstorm. Model solutions diverge in their handling of a
secondary upper wave forecast to advance across southern Hudson Bay
Tues night/Wed. The GFS camp drives this wave south into the Great
Lakes region on Wednesday, while the ECMWF/UKMEt/Canadian all shear
this wave eastward into northern Quebec. These differences will
impact the degree of cold air advection (if any) Wed into Thursday
with the GFS being quite a bit colder. The current ensemble blend
forecast will feature late week temps just slightly below seasonal
averages attm.

MARINE...

Cooler post-frontal westerly flow continues through the evening as
gusts generally top out in the 20-25kt range, though near 30kts
possible over the Saginaw Bay. An upper level trough currently
settling over the Great Lakes holds overhead through the weekend
leading to fairly consistent day-to-day conditions for the central
Great Lakes. Some variability in wind direction (between west and
northwest) is likely as disturbances embedded within the trough
swing across northern Ontario. The cooler airmass maintains unstable
overlake thermal profiles to support efficient mixing of winds down
to the surface resulting in moderate winds through this timeframe
with peak gusts for the majority of the region between 20-25kts. The
exception will be northern Lake Huron where winds have the best
potential to reach 30kts. Small craft advisories remain in effect
for the Saginaw Bay and tip of the Thumb nearshore waters through
Saturday afternoon due to a combination of winds and waves. These
waters likely will require another advisory daytime Sunday as
rougher conditions look to redevelop.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory until 4 PM EDT Saturday for LHZ421-422-441.

Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&

$$

AVIATION.....AA
DISCUSSION...SC
MARINE.......KDK


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