Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000 FXUS63 KDTX 211104 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 604 AM EST Wed Feb 21 2018 .AVIATION...
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Rain will continue early this morning as a wave of low pressure lifts northeast along frontal surface. Once this low passes, the front (and rain) will shift east of the terminals. This will occur in the 13z-16z time frame. Moisture convergence along the front should produce generally MVFR to occasional IFR ceilings with improvement midday today as drier northwest flow increases. VFR conditions will be prevalent to end the forecast period. For DTW...Persistent rain will hold on over the terminal until 15z- 16z before shifting east. Ceilings will drop to MVFR (IFR at times) with this activity. Frontal passage will bring northwest winds today which will become north with time by evening. /DTW THRESHOLD PROBABILITIES... * High for ceilings AOB 5000 feet through this morning, low thereafter.
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&& .PREV DISCUSSION...
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Issued at 335 AM EST Wed Feb 21 2018 DISCUSSION... Active forecast for the next week as a series of waves continues to eject out of the longwave trough over the west coast and up through the Great Lakes region. Seemingly each time the main wave gets ejected, it is quickly back filled by the next wave dropping into the trough. Thus each time it looks like the pattern will break for a while, it quickly returns to a positively tilted trough. Broad upper ridge over the SE conus will meander about through this process, largely keeping the main baroclinic zone and upper level jet near or over the state. Models want to largely keep SE MI on the warm side of this baroclinic zone though some of the shortwaves will brush us with cooler air on occasion. Overall temps look to hover a few degrees above normal through the end of the month. The flood watch will continue through this afternoon as the rain continues to fall. Most locations to this point have received around 1.5 to 2 inches of rain. This has lead to several area rivers reaching flood stage already with a few others forecast to reach flood stage over the next day or so. A cold front over Mid MI will drop through SE MI by this afternoon bringing an end to the rain but not before another 0.25 (Saginaw Valley) to 1 inch (Ohio Border) of rain falls. A very healthy fetch of moisture seen on water vapor extends from the Gulf of Mexico up into Michigan continuing to feed this dynamic pattern producing all the rain. In addition to the frontal forcing in place, the next mid level shortwave riding along the front is entering southern MI at press time which will bring another window of widespread moderate showers to the area. Once this wave lifts through the front won`t have much residency time left before exiting the area itself around noon. All in all it still looks like a wide swath of 2-3 inches of total rainfall will occur across the region with some locally higher amounts possible. Strong area of high pressure will spread across the central Great Lakes this evening and overnight bringing a stretch of dry and quiet weather. It will also be cooler as high temps top out in the upper 30s Thursday. There is a slight chance of some light snow Thursday morning south of I94 as the next shortwave riding up the frontal zone tries to bleed across the MI/OH border. With the dry air in place with the strong surface high and northerly flow, it will be hard for anything to make it this far north. Will leave a low pop in for the moment to acknowledge the possibility. Next opportunity for precip will come late Thursday night into Friday as the next system ejects out of the trough through the region. As with this current system, there appears to be some phasing of northern and southern stream waves which will lead to another feed of Gulf moisture into the system though not as moist as this current airmass. A warm front will lift up through the area early Friday which model thermal profile want to favor a wintry mix north of the front before the warmer air surges in turning it to all rain through the afternoon. After a short period of high pressure Friday night, yet another system will lift through the region Saturday and Saturday night bringing mostly rain once again. MARINE... Low pressure will lift northeast of Lake Huron early this morning a trailing cold front pushing southeast through the region in its wake with winds shifting to the northeast for all marine areas. Increased instability in the colder air mass will allow gusts to approach 30 knots this morning across northern Lake Huron. High pressure will build into the region tonight and cause winds to decrease. Winds will then veer to the northeast on Thursday. Winds then shift from the south into Friday as the next low pressure system brings additional rain. HYDROLOGY... Rain will continue early this morning before shifting to the east with a cold front during the mid to late morning period. Additional rainfall of one quarter to one half an inch will be possible with a few higher amounts possible over far southeast lower Michigan near the Michigan and Ohio state line. A Flood Watch will continue into today as this additional rainfall will only exacerbate potential flooding after the 2 to 3 inches of rain that has fallen over the past few days. Many area rivers and streams will be at or above flood stage with ponding of water in low lying and poorly drained areas also anticipated.
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&& .DTX WATCHES/WARNINGS/ADVISORIES...
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MI...Flood Watch until 4 PM EST this afternoon for MIZ047>049-053>055- 060>063-068>070-075-076-082-083. Lake Huron...NONE. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE.
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&& $$ AVIATION.....DG DISCUSSION...DRK MARINE.......DG HYDROLOGY....DG You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.

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