Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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384 FXUS63 KMQT 230759 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 359 AM EDT Thu May 23 2024 .KEY MESSAGES... - Another shortwave and low pressure system will bring another round of showers and a slight chance (around 20% chance) for some thunder to Upper Mi late Friday into early Saturday. - There will be more opportunities for rain next week although model uncertainty leads to low forecast confidence on timing/extent. && .SHORT TERM /THROUGH TONIGHT/... Issued at 318 AM EDT Thu May 23 2024 RAP analysis shows a stacked closed low north of Lake Superior with central surface pressure near 994 mb. While a tight pressure gradient and tapping into a LLJ caused windy conditions earlier, the weakening low departing the region is allowing winds to come down somewhat, though some gusts to 25 mph may linger throughout the morning. Despite weakening surface flow, diurnal heating will support cu development with a few CAMs suggesting some shower development in the south and interior west. Instability has trended lower with the last 24 hours of model runs, so confidence in showers of any strength is low, but left some 15-24% PoPs from 18Z to 02Z. Expect highs mainly in the mid 60s, close to the climatological normal for this time of year. The exceptions will be locations downwind of Lake Superior that will have highs near 60 and the south, which bias- corrected guidance suggests mid- to upper-70s may be observed between Menominee and Iron Mountain. Overnight, winds turn easterly and northeasterly in response to a 00Z GEFS-mean 997 mb low approaching Minnesota. Previous forecasts had rain arriving in Ironwood by 12Z Friday, but virtually all of the most recent model runs at varying resolutions have backed off on the initial line of precipitation, so PoPs have been largely removed from the overnight time period. Low temperatures will be in the 40s, near normal for this time of year. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Issued at 354 AM EDT Thu May 23 2024 Several models and ensembles showing signs the pattern could remain fairly active and wet from late this week into early next with probably a period of drying for the middle of next week (Wed-Thu). By Friday, the focus will shift to the next shortwave emerging from the western CONUS mid-upper level trough. This shortwave lifts NE through the Plains and Upper Great Lakes, eventually swinging into Manitoba and Ontario phasing once more with the broader troughing over the western CONUS/Canadian Prairies. Increasing isentropic ascent, 850 mb theta advection and moderate q-vector convergence out ahead of the shortwave will lead to another quick round of showers across the area beginning late Friday afternoon in the western UP and spreading eastward during the evening. Instability off soundings looks pretty minimal for thunder so probably only isolated t-storm coverage at best. Otherwise, guidance continues to favor amounts widespread amounts of 0.10-0.30 inch, but EPS ensembles also show probabilities of 40-60% for amounts of 0.50 inch or more south central and southeast before the showers lift east of the area with the exiting shortwave/front by late Saturday morning. Saturday for the most part should be dry with ridging/subsidence behind the exiting shortwave. Expect otherwise partly cloudy skies and seasonable temperatures for the rest of the day with highs mostly in the 60s with a few cooler mid 50s readings near Lake Superior. Bigly model uncertainty rears its ugly head in the Sunday-Tuesday time frame regarding the track/strength of the next western CONUS wave and developing cyclone ejecting NE from the lee of the southern Rockies into the Great Lakes region late weekend into early next week as many of deterministic models (particularly the GFS, UKMET and Canadian) have been flip- flopping over solutions more in the past few days of runs than a politician in an election cycle. One model run will show a weaker, suppressed system tracking well south with no impacts for the UP, with the next run showing a deeper system tracking north through Lower Mi indicating greater rain and wind impacts for the UP late Sunday into at least Monday. The ECMWF, on the other hand, has been the most consistent of the models advertising generally a more phased and deeper system for the last several runs with a more northern/western track through the Central Great Lakes, and thus, greater rain and wind impacts for Upper Mi in the late Sunday into Memorial Day time frame. That said, the latest 00Z Thu and 12Z Wed ECMWF runs did back off a bit from its much deeper, northward 00Z Wed solution through the Mackinac Straits and now instead has a slightly more suppressed track through central Lower Mi on Monday, more in line with the fcst EPS and GEFS mean tracks. However, given the huge spread depicted in the tracks of the ensemble members it`s still too soon to latch onto any one model solution with great certainty, thus leading to poor forecast confidence during this time frame. For now, will go with the model blend for forecast details and wait a bit longer for models to sort out their continuity/consistency issues and hopefully come into better agreement over the coming days. Most of the models and ensembles (with the exception of the latest 00Z GFS run) do seem to be in general agreement showing a trend toward ridging and drier conditions for Wednesday into Thursday next week. && .AVIATION /06Z TAFS THROUGH 06Z FRIDAY/... Issued at 123 AM EDT Thu May 23 2024 In the wake of low pres tracking ne across northern Ontario, drier air moving into the area will allow VFR to prevail at IWD/CMX/SAW thru this fcst period. W to NW winds will still be elevated into this aftn, especially at CMX/SAW. Expect w to nw winds of 15-20kt at CMX thru late aftn. Winds at SAW will increase to 15-20kt a few hrs after sunrise. Winds will become light, aob 5kt, at all terminals this evening. && .MARINE... Issued at 354 AM EDT Thu May 23 2024 Fairly deep low pressure centered over northern Ontario early this morning will gradually shift ene to near James Bay later this morning and remain nearly stationary into this evening before shifting e into Quebec later tonight. As the low shifts east with time, it will be replaced by a weak high pressure ridge over Lake Superior today. Winds have diminished significantly across the lake this morning and should drop below 20 knots across the lake this afternoon into this evening. The period of light winds doesn`t last long over the western lake however as northeast winds will begin to ramp up to 30 knots late tonight into Friday in advance of another low pressure lifting from the Northern Plains towards Lake Winnipeg. Guidance indicates around a 30-40% chance for gale force gusts Friday into Friday evening over the western quarter of Lake Superior. East to southeast winds gradually increase over the east half of the lake on Friday but generally stay 20 knots or less but could briefly gust near 25 knots over northern portions of the lake Friday night as winds veer more southerly in advance of associated cold front from the Plains system. Winds over the west half becoming southwest behind the low and the passage of its cold front late Friday night into Saturday and generally stay in the 15 to 25 knot range. Behind this system, expect light winds of 20 knots or less across Lake Superior for the rest of this weekend as a high pressure ridge builds over the area. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...GS LONG TERM...Voss AVIATION...Rolfson MARINE...Voss