Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 241953
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
353 PM EDT Fri Mar 24 2017

.DISCUSSION...

Upper low centered over northern Texas and Oklahoma will slowly
track east through the Plains tonight and Saturday, before beginning
to lift northward towards the Great Lakes. The frontal boundary
currently draped over central Lower Michigan will sink slowly
southward tonight as high pressure builds through Ontario and
Quebec. Main area of precipitation now over Northern Michigan and
Wisconsin will settle southward as well, filling in some as the
convergence along the front tightens in response to right entrance
region forcing from a jet streak passing through the northern Great
Lakes and eastern Canada. The FGEN forcing should provide a fairly
steady rainfall along elevated portions of the frontal boundary
tonight into Saturday, before the jet streak slides east. Main area
of rainfall will sink into the northern portion of the forecast area
this evening and tonight. Another area of rainfall is looking to
develop this evening further south, however, and should affect the
Detroit area.

Forecast models, including all higher-res runs, continue to develop
another area of showers ahead of the surface front this evening, as
it reaches roughly near the M-59 corridor southward. The increase in
activity looks to be in response to low-level convergence increasing
as the front encounters strong southerly flow, and as a modest theta-
e surge makes its way up into Michigan from Illinois/Indiana.
Stability indices continue to hint that thunder may be a possibility,
but forecast soundings show enough of a cap to justify leaving the
mention of thunder out. Rain should then fill in over all of
Southeast Michigan by early Saturday morning as the elevated portion
of the front slides solidly over the area. High coverage/more steady
rain should continue through about mid-day before it likely tapers
to showers as upper jet support is lost. Showers will then continue
through Saturday night and Sunday as the upper low lifts northward
and pushes the front back northward into the area. Activity on
Sunday should be more convective in nature, with a few thunderstorms
even possible, as the upper low and associated cold pool work
across.

Clearing and mixing into very warm air aloft has pushed temperatures
into the upper 60s to low 70s this afternoon on the south side of
the warm front. Temperatures tonight will show wide variation as the
front slowly slides through the area, dropping into the mid 30s for
the northern portion of the area and the upper 40s near the Ohio
border. Not much temperature recovery is expected during the day
tomorrow as Southeast Michigan remains on the north side of the
surface front, under clouds and rain, and we see stiff east to
northeast winds off the colder lake waters (especially Lake Huron).

A slight chance for spotty showers will exist throughout Monday as
southwest winds continue to advect warm, moist air into the region.
PoP values will steadily increase Monday night into Tuesday morning
as low pressure pushes from Missouri, into the Ohio Valley. The
chance for rain will gradually diminish throughout the day on
Tuesday as high pressure moves in from the Northern Central Plains
into the Great Lakes region late Tuesday into Thursday morning,
keeping conditions relatively dry through that period.

The next chance for precipitation will return Thursday into Friday,
as the GEM and ECMWF 12Z suites pick up on low pressure moving from
Texas/Oklahoma into Michigan. High uncertainty still exists
regarding both the timing, track, and strength of the potential low.
For comparison, the GFS long-range run keeps the system well to the
south of Michigan, centering it across Kentucky Friday night and
into West Virginia by Saturday morning.  This feature will be
something to keep an eye on as we approach next week.

&&

.MARINE...

Frontal boundary over Central Lake Huron his afternoon will sink
south tonight as high pressure builds into Ontario, leading to
northeast winds of 15 to 25 knots over Lake Huron tomorrow with
gusts briefly up to 30 knots over the mid section of the Lake early
tomorrow morning. This will lead to waves in excess of 4 feet
impacting the nearshore waters over the northern Thumb region during
the day, and small craft advisories have been issued. Winds will
become a bit more East-Southeast for the second half of the Weekend
as low pressure tracks through the western Ohio Valley and into
Lower Michigan Sunday Night. The weak low then looks to slowly pass
through Lake Huron on Monday, with generally light winds right into
Tuesday, but from the north behind the low.

&&

.HYDROLOGY...

Periods of showers Tonight and right through the weekend as a
frontal boundary meanders over southern Lower Michigan. Rainfall
totals are expected to approach 1 inch across much of the area, but
flooding is not expected due to the long duration and intermittent
nature of the rainfall. Runoff from the rainfall will increase flow
rates and water levels in local streams and rivers.

&&

.PREV DISCUSSION...
Issued at 113 PM EDT Fri Mar 24 2017

AVIATION...

Just mid clouds around early this afternoon as majority of southeast
Michigan resides solidly in the warm sector, promoting strong
southwest wind gusts of 25 to 30 knots across southern TAF sites.
The frontal boundary over northern Lower Michigan will be on the move
to the south by early this evening, helped out by sunset and the
cold flow off Lake Huron.

Modest surface based instability has built up toward the Ohio border
this afternoon, and there is a very low risk of a thunderstorm early
this evening as front drops south.

Low clouds should easily develop and lower this Evening/Tonight as
low level front produces showers, and expected to reach IFR
conditions, with Likely LIFR conditions at all TAF sites late
Tonight, with little to no improvement Saturday morning as the front
remains stalled and showers and drizzle persists.

For DTW...SOUTHWEST winds near 20 knots sustained, gusting to 30+
knots early this afternoon will subside toward sunset, becoming
light during the evening hours, with wind shift to the northeast
occuring by midnight. Easterly winds (around 10 knots) then look to
prevail overnight into Saturday. High confidence in borderline
IFR/LIFR conditions developing Tonight, and moderate for LIFR
conditations.

//DTW THRESHOLD PROBABILITIES...

* High for cigs aob 5000 FT after 00z this evening.

* Low confidence in cigs/vsby aob 200 FT or 1/2SM late tonight into
  early Saturday morning.

* High guidance in southwest gusts exceeding 25 knots this afternoon.

* Very low risk of a thunderstorm early this evening


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory from 6 AM to 8 PM EDT Saturday for LHZ422.

     Small Craft Advisory from 6 AM Saturday to 4 AM EDT Sunday for
     LHZ421-441.

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

$$

DISCUSSION...HLO/AM
MARINE.......SF
HYDROLOGY....SF
AVIATION.....SF


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