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FXUS63 KDTX 260710
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
310 AM EDT Wed Sep 26 2018

.DISCUSSION...

The very moist airmass (lower 70 surface dew pts/700 MB dew pt of 6
C per 00z DTX sounding) which helped spawn a couple tornadoes in
Monroe/southern Wayne counties has already peeled off to the east,
and today will be noticeably cooler and drier following the cold
frontal passage early this morning. 00z Minneapolis sounding
indicated an 850 MB temps of 3 C, so with the cold advection through
the day, temps likely holding in the 60s, but Detroit stands an
outside shot at hitting 70 degrees with at least partly sunny
skies/increased mixing depths and favorable westerly wind.

Upper level southwest confluent flow tonight, with center of surface
high sliding through the Ohio Valley, thus locations toward the
southern Michigan border stand best chance of winds going calm, and
subsequent cooler temps, around 40 degrees. Otherwise just about
everybody in the 40s.

Next strong upper level wave/trough diving into the northern
Mississippi River Valley on Thursday, with the 850-700 MB
Theta-e/moisture axis tracking through southeast Michigan close to
12z Friday. Very narrow moisture axis and lack of instability
(showalter index 3+ C), good chance the front comes through dry.

Secondary jet streak/upper level energy rounding the base of the
trough late Friday/Friday night could illicit mid level fgen
response and possible showers as 500 MB trough axis slides through
the Central Great Lakes early Saturday. 850 MB temps falling at or
slightly below zero will set up a cool weekend, with the potential
for frost Saturday night (dependent on upstream warm advection clouds
spilling over). Upper level northwest confluent flow/surface high
will hold for Sunday, with warm front then lifting north through the
Western Great Lakes Sunday night, with pretty good west-east aligned
moisture axis (PW Values around 1.5 inches) spreading into lower
Michigan Sunday night-Monday. Exact location of the good over-
running rain/fgen zone remains in question, but it appears areas
north of I-69 stand the best chance of a soaking rain early next
week.

&&

.MARINE...

Stronger northwest winds will exist across the area today in the
wake of an early morning cold frontal passage. The strongest winds
remain across the northern Lake Huron basin, where gusts will reach
around 30 knots through the early afternoon hours. This wind
direction and strength will build wave heights over central
sections of Lake Huron. This will allow wave heights along the
nearshore waters to reach near small craft conditions for a time
early today. Winds diminish late today and tonight as high pressure
builds into the region. Winds then turn southwesterly and
strengthen again Thursday in advance of the next cold front. This
front is forecast to sweep through the region early Friday, bringing
another period of stronger northwest winds on Friday.

&&

.PREV DISCUSSION...
Issued at 1235 AM EDT Wed Sep 26 2018

AVIATION...

Cold front on track to lift across the region during the early
morning period. Diminishing window in advance of this boundary for
additional shower and thunderstorm development, albeit within an
increasingly stable environment. Frontal passage centered 08z-10z,
accompanied by an increase in MVFR stratus and a wind shift to
westerly. The westerly winds will strengthen and turn gusty through
the morning period under modest cold air advection. Gusts to 20
knots or slightly greater expected into the afternoon. A period of
moderate mixing will lift ceilings into VFR with a general reduction
cloud coverage this afternoon. Clear skies with diminishing westerly
winds tonight. Fog potential Thursday morning appears limited by
continued light westerly gradient and a drying low level
environment.

For DTW...The cold front will advance across metro between 09Z and
10Z, veering the winds to the west. Small potential remains for
thunderstorm development in advance of this front. Post-frontal
westerly winds will turn gusty Wednesday morning. Potential does
exist for gusts to briefly reach crosswind thresholds.

DTW THRESHOLD PROBABILITIES...

* High for ceiling aob 5000 ft through Wednesday morning. Moderate
Wednesday afternoon.

* Low confidence that westerly winds will exceed crosswind
thresholds on Wednesday.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory from 6 AM this morning to 4 PM EDT this
afternoon for LHZ421-441.

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

$$

DISCUSSION...SF
MARINE.......MR
AVIATION.....MR


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