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000
FXUS63 KDTX 250807
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
407 AM EDT Thu Apr 25 2024

.KEY MESSAGES...

- A Freeze Warning is in effect for all of southeast MI through 8 AM
as temperatures remain into the mid to upper 20s.

- Dry conditions with a warming trend bring high temperatures to the
50s today and 60s on Friday.

- Showers are likely Friday night into Saturday morning with breezy
and warm conditions this weekend. There is low confidence in shower
and thunderstorm potential for the latter half of Saturday and
Sunday.

&&

.DISCUSSION...

An extremely dry air mass is in place, characterized by PWAT of
0.14" observed in the 00z DTX sounding. For context, this is the
lowest late April PWAT recorded at our site since 00z 4/26/2000 per
SPC climatology. No surprise that skies are clear this morning and
temps have dropped well into the 20s away from the lakeshore and
urban footprint. The Freeze Warning remains in effect until 8 AM.
With high pressure parked overhead, temperature advection will be
nil today but do expect the abundant sunshine to bring a notable
improvement to the brisk conditions from yesterday. High temps in
the mid 50s look on track this afternoon with light wind mainly out
of the east. Lows tonight look to settle to the lower to mid 30s.
Modest lake moisture flux within the easterly flow and more of a
gradient tonight will prevent another widespread hard freeze, but
areas of frost are certainly plausible.

On Friday, a low pressure system will strengthen over the central
Plains in response to a strong mid-level wave passing over the
Rockies. This amplifies the ridge axis in place over the Great Lakes
and maintains dry and stable conditions through the daylight hours.
High clouds will steadily increase over the course of the day as the
Plains system`s warm conveyor begins to advance in from the west.
Better low-level moisture advection should hold off until the LLJ
veers into the southern Great Lakes, likely after dark Friday
evening. This air stream will have origins in the western Gulf and
will rapidly moisten the column with PWATS rising in excess of 1
inch overnight. A band of showers will likely pivot through
overnight into Saturday morning as the LLJ drives a corridor of
strong warm/moist ascent up the progressing warm frontal slope.
Models continue to suggest some embedded thunderstorms will be
possible given the strong upward vertical motion. Lapse rates near
moist adiabatic will offer little elevated instability and a strong
near-surface stable layer will result from the elevated warm
advection, thus severe storms are not anticipated.

As the Plains wave eventually tracks from the Upper Midwest into
Ontario on Saturday, it will weaken and shear across the longwave
ridge over the eastern half of North America and modest height
rebounds are likely across the Great Lakes. We will be positioned
within the warm sector as the surface low races well to our north,
leaving its cold front draped nearly stationary across the western
Great Lakes. This feature will be the main forcing mechanism for
convective activity on Saturday afternoon, and think the brunt of it
will remain to our north and west. However, there will remain at
least a chance of showers and storms Saturday afternoon as the sfc-
850mb theta-e ridge moves in with relatively weak capping in place.
MLCAPE building to around 500 J/kg with a belt of 40 kt
southwesterlies aloft will bring the potential for stronger storms
if convection does fire, especially late in the day. SPC has
highlighted parts of the region in a Day 3 Marginal Severe Risk.
Temperatures will trend up to the mid 70s for a high and breezy
southwest wind looks to gust around 25 to 30 mph.

A second low pressure system develops over the Plains on Sunday and
tracks northeast along the stalled frontal boundary into the
Midwest. Have high confidence in another day spent in the warm
sector with temps well into the 70s - possibly 80s for some spots.
Lower confidence exists on convective trends at this stage. Models
have varying depictions of placement/strength of the LLJ and
potential for a secondary warm frontal passage which would be the
main forcing mechanism. Meanwhile, mid-level ridging will likely
undergo another period of modest amplification as the low deepens
well to the west, and this may provide a less favorable background
environment for convection. Will hold on to the inherited
chance/likely PoPs but can expect significant revisions for this
period as we glean additional insight. Higher confidence does exist
in cold frontal passage on Monday that will likely direct a round of
showers and storms across the area. Only weak cold advection is
shown behind this system so expect above normal temps through the
bulk of next week.

&&

.MARINE...

The influence of high pressure will maintain lighter wind speeds
through the day into tomorrow morning. Low pressure, derived from
the Panhandle of Texas, will then fill in across the western
Midwest, while the aforementioned high pressure system settles over
New England. This will strengthen the pressure gradient across the
Great Lakes, bringing elevated winds and gust potential centered
Friday afternoon into Saturday morning. The peak gust potential is
expected by Saturday morning, where gusts just shy of gales, or
occasional gust to gales, will be possible across Lake Huron. Very
stable over-lake conditions will be in place during this time as
warm air filters over the cooler waters, so the expectation is that
the increased stability will help prevent sustained mixing of gust
to gales. Widespread showers with some rumbles of thunder will be
likely Lake Friday into Saturday morning as a warm front moves over
the region.

&&

.PREV DISCUSSION...
Issued at 1137 PM EDT Wed Apr 24 2024

AVIATION...

High pressure across the northern Great Lakes will expand across
southern Michigan overnight. Dry air will ensure mainly clear skies
tonight and  Thursday morning. There is some remnant clouds over
central Lake Erie. Recent model soundings are indicating that some
of this moisture will advance into metro Detroit late Thurs morning,
possibly resulting in FEW to SCT clouds aob 4k ft. The gradient will
remain light through the day Thursday, supportive of east-
southeasterly winds under 10 knots.

DTW THRESHOLD PROBABILITIES...

* None.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Freeze Warning until 8 AM EDT this morning for MIZ047>049-053>055-
     060>063-068>070-075-076-082-083.

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

$$

DISCUSSION...TF
MARINE.......AM
AVIATION.....SC


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