374
FXUS63 KDTX 190757
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
357 AM EDT Sun May 19 2024

.KEY MESSAGES...

- Warm and muggy conditions are expected today and during the early
part of the week with daytime highs in the 80s.

- Showers and thunderstorms are likely this afternoon from Port
Huron southwestward to Adrian including Metro Detroit. Brief heavy
downpours and gusty winds are the main concerns this afternoon.

- Chances exist for thunderstorms Monday afternoon mainly north of I
69. There will be a potential for strong to severe thunderstorms,
but low confidence exists with exactly the strong to severe threat
will occur.

- A much less humid airmass is expected for the end of the week.

&&

.DISCUSSION...

A dynamic upper level jet streak is forecasted to broaden today
while lifting to Hudson Bay. The broadening will force geopotential
heights to flatten across Lower Michigan which will not only allow a
surface cold front to settle southward through northern Lower
Michigan but also result in increasing boundary layer warming
immediately ahead of the approaching cold front. A notable but
narrowing thetae plume is expected to be in place during peak
heating this afternoon with forecast soundings supporting a well
mixed boundary layer of upwards to 4.0 to 6.0 kft agl. An
interesting scenario for this afternoon as a strong consensus of
hiresolution models support convection over the southeastern 2/3rds
of the cwa. This is despite fairly convincing background
anticyclonic vorticity advection over all of the forecast area and a
resolved weak 700mb anticyclonic circulation pushing overhead. At
first glance of the environmental wind profile, cell movement would
appear to be light west to east. However, the strong consensus in
convection this afternoon is unanimous in a slow northeast to
southwest track that is in agreement with the backward propagating
Corfidi vectors.

Based on the model support, increased PoPs into the likely-numerous
category for the afternoon in southeast sections of the forecast
area. Trigger/lifting mechanisms are expected to be near the
shorelines where increased convergence is located due to
differential heating. Do not really see a true lake breeze signal
per se, but convection will likely behave similarly with the
backbuilding and convective reinforced outflow.  Very little to no
shear suggest no strong or severe thunderstorm risk. The main threat
with the convection will be heavy rainfall due to slow storm
movement. Precipitable water of 1.3 inches and flow aligned along
the axes of lift increases the concern. Will forgo any thoughts of a
Flood Watch due to an extremely small footprint to any modeled
convective cells and a favorable setup for anticyclonic vorticity
advection. Gusty winds due to pulse type-water loading and small
hail (Surface based CAPE in excess of 1000 J/kg) will be possible.

An upper level trough pushing into the Pacific Northwest will cause
downstream amplification to a ridge over the central United States
Monday and Tuesday. The cold front that approaches the area today
will quickly lift northeastward on Monday. Some uncertainty exists
with the Monday afternoon forecast as trends suggest upstream
convective activity from the Plains will approach northern Lower
Michigan Monday afternoon. Convective parameters are in the ballpark
to support a threat of severe weather. Mixed Layer CAPE is
forecasted to reach and exceed 1750 J/kg and 0-6km bulk shear will
possibly reach/exceed 35 knots. While the magnitude of the bulk
shear suggests some potential for mesocyclones, the morphology of
the cam output suggests convective line with possible forward
propagating characteristics. The severe threat will likely hinge on
the track of convective vorticity which points to northern Lower
Michigan. Will need to monitor trends in future model data as SPC
has included Southeast Michigan in a Marginal risk for severe
weather. The majority of the models are dry here for Metro Detroit
but many including the latest ECMWF are bullish on late afternoon
convective activity near Saginaw Bay and Lake Huron. Expect
revisions to the convective Outlooks. Southeast Michigan will be
well within the warm sector with an unstable air mass and highs on
Monday expected to again reach the middle 80s. The inherited
forecast included a range of slight chance to chance for the
northern forecast area.

Uncertainty continues into Tuesday as convectively augmented
vorticity maxima will have the potential to stream out of the trough
toward Southeast Michigan. A dynamic low pressure system is progged
to wrap up over the northern Mississippi River Valley Tuesday with
background forcing downstream again supporting large scale subsidence
over Lower Michigan. Confidence is not particularly high given the
favorable conditions for convection across the Plains, but there is a
signal for Tuesday morning activity then pushing out and drying for
the afternoon. Confidence is then reasonably high for a cold front
pushing through the area early Wednesday. Drying with dewpoints
falling into the 40s is expected to carry out the remainder of the
week.

&&

.MARINE...

Humid conditions persist with pockets of fog across the region this
morning. Fog should largely dissipate from Lake Huron early this
morning as southerly flow increases ahead of a cold front.
Meanwhile, fog expands across western Lake Erie and possibly into
Lake St. Clair as light southeast wind persists there. This should
mix out by midday. Today`s cold front will be weak but may produce
isolated showers or thunderstorms this afternoon and evening,
especially along the nearshore waters. An area of low pressure then
tracks in from the Midwest late Monday into Tuesday, bringing the
next chance for showers and storms with the highest likelihood
across northern Lake Huron. Winds and waves are expected to remain
below Small Craft Advisory criteria outside of any localized higher
winds within any thunderstorms. A period of stronger south wind is
increasingly likely late Tuesday night into Wednesday as a stronger
low and associated cold front lift into the region.

&&

.PREV DISCUSSION...
Issued at 1154 PM EDT Sat May 18 2024

AVIATION...

Will maintain a mention of fog KYIP/KDTW/KDET within light southeast
flow from Lake Erie, but will temper the degree of lower stratus as
late evening satellite trends do not support much stratus at this
point. Winds veer to the southwest and then west as a weak frontal
boundary settles into the area. This front, combined with a number
of lake breeze boundary, will be the focus for widely scattered to
scattered showers/thunderstorms late in the day, mainly KPTK south.
Wind will shift to northeast tomorrow night behind the front and
then basically become light/variable.

For DTW/D21 Convection...There will be a chance for scattered
thunderstorms Sunday afternoon as a weak frontal boundary interacts
with lake breeze(s) serving as the focus. Isolated heavy downpours
may bring visibility restrictions.

DTW THRESHOLD PROBABILITIES...

*  Low for ceilings aob 5kft late tonight.

*  Low for thunderstorms Sunday afternoon.


&&

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

$$

DISCUSSION...CB
MARINE.......TF
AVIATION.....DG


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at www.weather.gov/detroit.