Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
FXUS63 KDTX 201620
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1220 PM EDT TUE SEP 20 2016
An increasingly dry column and surface high pressure will support
VFR and light winds through the period. Some sites already
exhibiting somewhat variable wind behavior this afternoon. With
calm to variable winds expected overnight, will go ahead and
simplify TAFs with a blanket VRB beginning at 18z...the
implication being that there will be a tendency for occnl NE
component today tending toward more southerly by morning. Wind
speed generally 5kts or less through this time.
For DTW...Periods of NE wind are expected to remain below noise
//DTW Threshold Probabilities...
Issued at 322 AM EDT Tue SEP 20 2016
Cold front will continue to push through Southeast Michigan early
this morning. At 3AM there was a narrow line of showers working
eastward from Western Michigan, aligned along a narrow ribbon of
theta-e. These showers will try to ride over the area but will
encounter the dry airmass shown by 00Z DTX raob. Any rain that falls
will be very light, with the expectation for most returns to only
yield virga or sprinkles. Showers are expected to end just after
sunrise as the front slides south.
Upper low centered over northeast Manitoba will lift into St James
Bay today, while another upper low drops through the Pacific
Northwest. This will prompt rising heights over the central CONUS
and Midwest, and allow surface high pressure to become established
over Michigan today into tonight. Dry, stable airmass will bring a
dry day with cu field mainly south of the M-59 corridor where mid-
level theta-e ribbon will be slower to exit. Sunshine, dry air and
little change in 925-850mb temps behind the weak front will yield
max temps only slightly cooler than yesterday, with highs reaching
the upper 70s to low 80s.
A warm front will then lift through Lower Michigan very late tonight
and Wednesday as the west coast low digs southward and subtropical
shortwave energy rides up into the plains, spinning up a large but
diffuse area of low pressure over the plains. Model forecast
soundings are showing a strong cap in place as good theta-e
advection works in with the weak warm front. Stability looks to
erode by late in the day and overnight however as heights begin to
fall and shortwaves eject out of the plains and up into the Great
Lakes. This should provide a chance for showers/tstorms from I-69
north from Wednesday afternoon through Thursday as the front remains
quasi-stationary over Northern Michigan. This frontal boundary
should slowly drop south again Thursday night through Friday as more
shortwave energy pivots south around the upper low over Hudson Bay
and a strong dome of surface high pressure sets up over Manitoba and
Ontario. This should spread chances for showers and thunderstorms
southward, through they may not quite reach the Ohio border per
latest model guidance regarding the frontal position. Cooler
temperatures (maxes in the upper 60s to low 70s) are then expected
over the weekend as cooler air settles in with Canadian high
Light winds and limited wave action will exist over the next 24
hours as high pressure gradually shifts across the region.
Developing southwest flow in the wake of this high will maintain
modest speeds. Frontal boundary sagging into northern portions of
Lake Huron will bring the potential for thunderstorms Wednesday
night and Thursday.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
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