Expert Forecast Opinion

445
FXUS63 KDTX 220827
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
327 AM EST Fri Nov 22 2024

.KEY MESSAGES...

- Breezy today with peak gusts around 30mph. Scattered to numerous
lake effect rain showers also likely today, mainly for areas east of
US-23/I-75.

- Dry weather returns for the weekend as weak high pressure builds
in. Lingering cloud cover will be difficult to dislodge however.

- Another low looking to develop over the region Monday bringing
additional rain chances and brief shot at milder air. Below normal
temperatures return by Tuesday and midweek.

&&

.DISCUSSION...

Broad, closed low upper trough continues to dominate conditions
across the Great Lakes/eastern CONUS today as its associated mature
surface low retrogrades into central NY. Gradient re-tightens across
the area this morning in response resulting in a deep column layer
of winds >30kts which will support surface gusts near 30mph for much
of the day. Northerly flow off Lake Huron aided by ribbons of
vorticity rounding the mid-level circulation into southern MI should
lead to a healthy lake effect response focused over the Thumb with
spottier chances spilling south into Metro Detroit. Areas to the west
of I-75/US-23 likely stay mostly if not entirely dry today given
their detachment from lake moisture plumes under NNW wind. Warmer
lake waters in the central/southern basin of Lake Huron (low to mid
50s F) modify the low level thermal profiles lifting freezing levels
to between 900-850mb and keeping p-types as rain. With the core of
thermal troughing now residing to our south and east, temperatures
are able to moderate some as highs climb back to around average in
the mid 40s.

Troughing influence wanes Saturday as low amplitude ridging over the
central CONUS attempts to nudge eastward into the central Great
Lakes. Weak surface high pressure accompanies said ridge supporting
drier conditions with seasonably average temps and lighter winds for
the weekend. However as it typical this time of year, sun may still
be hard to come by during this timeframe as forecast soundings
struggle to scour out remnant low level moisture given weak
subsidence and a lack of significant dry air advection (PW values
only drop by ~0.2").

Active pattern redevelops to start the new work week as a mid-level
shortwave breaks off from a larger Pacific NW trough and tracks into
the central Plains Monday. This wave is progged to reach the Great
Lakes late Monday into Tuesday as it undergoes amplification,
potentially gaining a negative tilt in the more aggressive
solutions, spurring surface cyclogensis over the region. How rapid
this amplification and subsequent cyclogensis occurs is the main
point of uncertainty with slower paces, such as what is in the Euro
deterministic/ensemble, resulting in surface low developing on top
of the area with the deepening and subsequent heavier precip
occuring to our east. Conversely a faster amplification such as the
GFS deterministic/ensemble leads to deepening occuring overhead
resulting in greater QPF. Regardless of either outcome, the bulk of
ensemble members in both families agree low development occurs
roughly over central lower MI leading to warm advection into SE MI
to keep the p-type as rain with much above average temperatures
reaching into the 50s. Strong cold air advection on the backside of
the low drops 850mb temps into the mid negative single digits (C)
likely supporting some snow being able to mix in with any lingering
trailing precip Tuesday.

&&

.MARINE...

The Great Lakes remain under influence of a slow-moving upper low,
which will continue to generate scattered lake-enhanced showers
through Saturday. The more notable part of this system is a second
round of strong northerly wind gusts that will funnel down the major
axis of Lake Huron today. A broad 925mb core of 35-40 knot winds
develops overhead, which will encounter very efficient momentum
transfer especially over southern Lake Huron where water
temperatures are around 12 C. Considering time of year, unstable
thermal profiles, and long fetch of unobstructed northerly flow, a
Gale Warning has been issued for the southern half of Lake Huron and
nearshore zones today. The most likely location for gale force gusts
up to 35 knots will be along the tip of the Thumb (Caseville to Port
Austin) and over southern Lake Huron around mid-day. Winds and waves
will subside very gradually on Saturday with mid-level ridging
attempting to build in briefly on Sunday. Another low pressure
system will be quick to develop over the Plains however to continue
the period of unsettled conditions into early next week.

&&

.PREV DISCUSSION...
Issued at 1139 PM EST Thu Nov 21 2024

AVIATION...

Ceiling heights have shown a wide variability from VFR to IFR
following the wake of the earlier region of precipitation. This
variability will persist into the predawn hours. Low level moisture
will then advance back into Se Mi from the northeast during the
course of the morning. This will trend ceilings heights to
predominately lower end MVFR. Areas of IFR ceilings can not be ruled
out. The degree of low level moisture may support areas of light
rain/drizzle. There will be an increase in the NNW gradient on
Friday. Despite limited mixing depths, the strengthening low level
wind fields will warrant forecast wind gusts in the 25 to 30 knot
range Friday afternoon.

DTW THRESHOLD PROBABILITIES...

* Moderate in ceilings aob 5000 ft tonight. High on Friday.

* High for precip type being all rain Friday.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory until 10 PM EST this evening for LHZ422.

Small Craft Advisory until 7 AM EST this morning for LHZ421-441>443.

Gale Warning from 7 AM this morning to 7 PM EST this evening for
LHZ421-441>443-462>464.

Lake St Clair...Small Craft Advisory until 10 PM EST this evening for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 10 PM EST this evening for LEZ444.

&&

$$

DISCUSSION...KDK
MARINE.......MV
AVIATION.....SC


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