Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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890 FXUS63 KDTX 221554 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 1154 AM EDT SAT OCT 22 2016 .AVIATION... Inversion above 3kft on 12z DTX sounding supports lake enhanced diurnal cu field remaining VFR through the period, particularly given shallow nature of moisture. Clouds will dimnish late in the day as moisture mixes out and gusty winds will subside by early evening with the loss of heating. Winds back to the SW tonight as mid-level cloud band over eastern WI moves across thea rea. For DTW...Visible satellite trends suggest broken ceiling by forecast issuance time. Stout nature of this morning`s inversion will likely keep cigs below 5kft. Expect to see a trend of thinning/dissipating cloud cover as early as 20z. Wind gusts pushing 25kt from the NW and therefore potentially causing crosswind issues will be short-lived as winds within the boundary layer weaken through the day. //DTW Threshold Probabilities... * Medium for cigs aob 5kft this afternoon. Low tonight after 06z. * Low for brief/marginal crosswind 300/25kt during the first 1 or 2 hours of the forecast. && .PREV DISCUSSION... Issued at 1007 AM EDT Sat OCT 22 2016 UPDATE... A forecast update was issued to adjust for latest cloud trends. Some fairly significant clearing has occurred over portions of the area since daybreak. The 12Z DTX sounding did show a deep inversion based at 860MB, much deeper than the bulk of most of the 06Z model suite suggested, including several hi res solutions. The moisture under the inversion is however very shallow. Subtle downslope into the Saginaw Valley and ongoing large scale subsidence has supported some areas of clearing. The low level flow will continue backing toward the west today. This will bring some remnant lake clouds into Se Mi. There will also be some diurnal cloud enhancement. Low level warming across Lake Mi today will however suppress the lake response. Increasingly divergent low level flow across Se Mi will also lead to an overall tendency toward mixing out some of the clouds. Taking all of these factors into consideration will likely result in a mix of sun and clouds through the first half of the day. The more widespread mid cloud deck now over ern Wisconsin and wrn Lake Mi is associated with mid level warm air advection and will eventually overspread the forecast area late this afternoon into the evening. PREV DISCUSSION... Issued at 325 AM EDT Sat OCT 22 2016 DISCUSSION... Slow release of the existing mid level cyclonic flow within the trailing section of the departing mean trough periphery will leave SE Michigan under generally benign northwest flow today. Cloud trends the primary challenge through the daylight period. A gradually drying north-northwest gradient this morning promoting a slow clearing process of the existing stratus, although satellite trends still present a mixed signal as to exactly how much clearing will commence yet this morning. Model evidence then continues to point toward the eventual eastward expansion of the residual lake Michigan moisture plume now tucked closer to the coastline. This advective process occurs in response to general backing of the mean flow toward the west with time, with this moisture capitalizing on a sufficiently steep lapse rate environment as diurnal heating takes hold. Increasing upper heights will yield a natural increase in mid level temperatures relative to yesterday, but expect lower levels to respond more slowly. Highs arrive in close proximity to yesterday, with readings in the vicinity of 50 degrees. There will be a noted diurnal uptick in northwest winds as well, with a gust component into the 25 mph range this afternoon. Pocket of higher mid level moisture will lift across the region tonight, as the surface ridge slips through and mid level flow briefly transitions to weakly anticyclonic. Presence of at least some degree of cloud cover and the eventual emergence of a light southwest flow will cap the cooling potential. Coldest locales could potentially achieve the mid 30s /thumb/ should a greater window of clear sky develop, but generally favor lows in the upper 30s/near 40F for many locations. Pattern of weak low level warm air advection develops on Sunday, existing low level southwest flow increasing immediately downstream of an inbound cold front. Mixing potential perhaps compromised some as mid level warm air advection remains stronger, but the noted warming across the lowest levels should still support readings into the 60 to 65 degree range. Compact shortwave will quickly track from the Upper MS Valley Sunday morning into central/southern Lake Huron by early Sunday night. Model response remains rather muted as this wave clips across central lower Michigan 21z-04z Sunday evening/night. Best response locally tied to the attendant cold frontal boundary, with frontal convergence increasing with time as trailing stronger height falls eventually catch the boundary. A simple chance pop mention still warranted for areas mainly M-59 northward during this time. Cooler post-frontal environment will define conditions Monday under prevailing northwest flow. Little expectation for the ambient airmass to moderate much heading into the midweek period. Extended guidance projects the development of low level easterly flow locally, downstream of a dynamic system organizing across the Plains. This tends to limit the diurnal response, particularly if an increasing coverage of cloud cover further caps an already meager mixing profile. This points to below normal temperatures across the Monday to Wednesday period. Dry conditions through at Tuesday under confluent mid level northwest flow and high pressure at the surface. MARINE... Northerly winds mostly in the 20 to 25 knot range over Lake Huron will become northwest Today, with just a slow diminishing trend Tonight. Small craft advisories remain in effect for the nearshore waters of southern Lake Huron, including Saginaw Bay. Winds will decrease to 15 knots or less on Sunday as the gradient finally relaxes across the region. This will be brief however as another push of cold air will support a reintesification of the northwest winds by Monday, with gusts around 30 knots over the open waters of Lake Huron. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...Small Craft Advisory until 4 AM EDT Sunday FOR LHZ421-441>443. Small Craft Advisory until 10 PM EDT this evening FOR LHZ422. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....JVC UPDATE.......SC DISCUSSION...MR MARINE.......SF You can obtain your latest National Weather Service forecasts online at is the U.S. government's official web portal to all federal, state and local government web resources and services.