Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000 FXUS63 KDTX 231039 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 539 AM EST Sun Feb 23 2020 .AVIATION... VFR with gusty southwest wind again today, though a noteable uptick in wind gust magnitide is anticipated. This will occur as the pressure gradient tightens during peak heating in response to low pressure translating across northern Ontario. For DTW...FEW-SCT at 050 possible along a weak frontal boundary as it settles through the area this afternoon. Ceilings then expected to deteriorate to MVFR late in the period as low pressure approaches from the south. DTW THRESHOLD PROBABILITIES... * Medium for cigs aob 5kft after 06z. && .PREV DISCUSSION... Issued at 306 AM EST Sun Feb 23 2020 DISCUSSION... Expect a mild day today as recent RAP/HRRR soundings suggest mixing will approach the 3-4kft height and tap into winds of 30 knots or a bit more. This should support the going forecast with highs pushing 50 most locations and wind gusts reaching 30 mph or so during best diurnal mixing this afternoon. Remaining snow cover along and north of the glacial ridge has not impacted mixing much the past few days so will assume the same will occur today. This should just impact surface temperatures slightly and will adjust downward a degree or so while upping temperatures the same amount where little/no snow cover remains from the Lake Erie basin in/around Detroit southward. A shortwave shearing west to east through Ontario today and on into Quebec tonight will allow a weak frontal boundary to settle into the region on Monday and bring a small degree of cooling as temperatures range from about 40F far northern area to perhaps 45F along the Ohio and Michigan state line. This temperature forecast assumes that the cloud cover will also increase substantially as southern stream low over the four corners region this morning ejects towards the region with mid/upper level clouds spreading northeast in advance of this system. This closed system will dampen considerably as it tracks into the Ohio Valley and southern Great Lakes Monday night and encounters substantive confluent flow. This will limit the northward push of moisture initially, but a strong trailing shortwave will already be digging southeast through the plains after coming onshore over British Columbia this morning. This will allow the initial southern wave remnants to lift north through the region Monday night as broad southwesterly flow becomes established. Additional shortwave energy will also begin to eject into area around this developing storm system to the west. This will maintain precipitation chances into Tuesday and Tuesday night. Low level temperature profiles suggest precipitation will fall as a mix of rain and snow during this time frame with primarily snow over the northern reaches of the forecast area and a tendency towards more rain over the far south. Lead band of precipitation will be fairly light on Monday night with a stronger FGEN forcing holding off until later Tuesday into Tuesday night as the influence of the western storm system becomes more prevalent. Snow accumulations will be possible, particularly over the northern half of the forecast area. With afternoon surface temperatures in the mid/upper 30s, most of this accumulation should hold off until late in the day Tuesday into Tuesday night. Additional snowfall can be expected Wednesday into Wednesday night as the main system ejects into the northeast CONUS and significant cyclogenesis occurs to the southeast/east of the area. With boundary layer conditions remaining borderline for rain/snow, accumulations most likely end up being highly variable with higher amounts favored over the north/northwest half of the forecast area and progressively lesser amounts southward. This will be especially true during the day Wednesday before colder air works into the area. By Wednesday night, the location/intensity of remaining precipitation will become highly dependent on the evolution of this winter storm. This remains uncertain, but should come into better focus as the northern stream energy is better sampled (especially by the 00z cycle). A colder weather pattern will then become established in the wake of this storm as additional jet energy continue to dig southeast into a large amplifying upper trough over the northeast quadrant of the CONUS. Highs in the 20s to around 30 will be common from Thursday into next weekend with lows at least down into the teens to single digits in spots. Snow shower activity will persist into Thursday before ebbing late in the week. MARINE... South-southwest flow will remain in place through Sunday allowing for moderation in temperatures. Favorable maritime conditions will continue through Monday afternoon with dry weather and light-to- moderate winds. The next system starts to move into the region late Monday. HYDROLOGY... Light precipitation is expected to spread north into the area on Monday night with an increase in coverage and intensity likely on Tuesday as low pressure encroaches on the area. This precipitation will fall as a mix of rain and snow across the area with snow favored north of M-59 and primarily rain south of I-94. Total rainfall equivalent will average around one third of an inch which will be too light to cause any flooding concerns. Additional rain and/or snow will also occur Wednesday into Wednesday night as a strong low pressure system deepens to the east of the area. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...NONE. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....JVC DISCUSSION...DG MARINE.......KDK HYDROLOGY....DG You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.

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