Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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815 FXUS63 KMQT 232356 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 756 PM EDT Thu May 23 2024 .KEY MESSAGES... - Another shortwave and low pressure system will bring a 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 344 PM EDT Thu May 23 2024 Current RAP analysis shows the mid level low along the southern end of James bay with it`s associated 995 mb low pressure center still over James bay, but just northwest of the mid level low. With weak sfc high pressure at around 1012 mb building over the CWA, mostly sunny skies have been the predominant sky conditions for much of the UP this afternoon. This has allowed for temps to warm up into the 60s for much of the UP; onshore flow has kept cooler temps along Lake Michigan between Manistique and the Mackinac Bridge as well as near Lake Superior. The sunny skies have also helped mixing yield a breezy day with west to northwest gusts up to 20-30 mph, strongest in the Keweenaw. Winds will gradually diminish into this eveing as high pressure continues to build in. Some diurnal cumulus has developed over the southern UP and will continue to increase this afternoon with the support of a mid level shortwave moving east through northern WI. Afternoon highs are expected to peak in the mid 50s to mid 60s near Lake Superior, 60s along Lake Michigan east of Manistique, and upper 60s to mid 70s elsewhere. Some slight chances for showers return to the forecast along the WI/MI state line with the best chances for showers in Menominee County late this afternoon where there is better instability (5/23 12Z HREF mean MUCAPE up to 250 j/kg in south central). Accumulations will likely be only a few hundreths at best, but showers moving through Menominee county could bring up to 0.1" to 0.2" of rain on the high end if the NAM Nest solution is favored. As daytime heating ends and high pressure continues to build in tonight, skies will mostly clear out helping temps settle slightly cooler than normal into the upper 30s to upper 40s. While mostly clear skies are expected with dry weather, cloud cover increases late into Friday ahead of the next low pressure system. This approahcing low will also turn light winds northerly then eventually easterly by Friday morning. && .LONG TERM /FRIDAY THROUGH THURSDAY/... Issued at 344 PM EDT Thu May 23 2024 Wet, active weather continues on and off through the extended period before we briefly dry out for the middle of next week. 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, with just a few hundred j/kg of CAPE indicated in HREF plots, so thunder should be fairly limited. Otherwise, guidance continues to favor widespread rain amounts of 0.10-0.25in, but EPS ensembles also show probabilities of 40-60% for amounts of 0.50in or more south central and southeast. Showers quickly exit eastward during the pre-dawn hours of Saturday with clearing skies expected as drier air works in. Saturday should be dry with ridging/subsidence behind the exiting shortwave. Expect 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. There remains quite a bit of uncertainty in the Sunday-Tuesday time frame regarding the track/strength of the next western CONUS wave and developing cyclone. This ejects NE from the lee of the southern Rockies into the Great Lakes region late weekend into early next week, but many of deterministic models (particularly the GFS, UKMET and Canadian) as well as ensembles continue to flip-flop on the exact track with some runs taking a deep system as far north as the Straits, and others suppressed more over the southern or central Lower Peninsula and coming in comparatively weaker. A more southerly route would have little if any wind and rain impacts to the UP, while the more NW route would bring a chance for more significant rainfall as well as gusty winds. 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. 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 continue to lean on 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. PoPs persist into Tuesday as the system moves into Quebec, and associated wraparound moisture curls into the area while another shortwave ripples through. Most of the models and ensembles do seem to be in general agreement showing a trend toward ridging and drier conditions for Wednesday into Thursday next week. Otherwise, expect more or less seasonable temperatures through the forecast period. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 754 PM EDT Thu May 23 2024 Dry air mass associated with sfc high pres ridge drifting across the area tonight will allow VFR to continue at IWD/CMX/SAW. Winds will also diminish to aob 5kt during the evening. On Fri, low pres lifting across the Northern Plains will swing an occluded front to the ne. That front will be approaching western Upper MI at 00z. Although some shra well ahead of the front may push into the w half of Upper MI mid and late aftn, the main area of shra and isold tsra will hold off until early evening. So, for now, fcst only reflects shra and MVFR cigs arriving at IWD around 22z. Shra/MVFR conditions will reach CMX/SAW just beyond this fcst period. During the aftn, E to SE winds will increase and become gusty to around 25kt at IWD/CMX and to around 20kt at SAW. LLWS will also be possible at IWD in the aftn. && .MARINE... Issued at 344 PM EDT Thu May 23 2024 Low pressure that impacted the area over hte past couple of days continues to weaken over James Bay while a weak high pressure ridge builds over the Great Lakes. Winds have been on the decrease today in response, still gusting to 20-25 knots out of the west in the eastern portions of the lake, but dropping below 20 knots to the west. Winds finally fall below 20 knots to the east later 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 60-70% chance for gales Friday afternoon through the early 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 25kt gusts will then become possible for a brief period into the evening and overnight hours. 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. Winds decrease late Saturday behind the exiting system, then 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. Looking ahead to early next week, another system moving out of the Plains will head towards the Great Lakes. This could present another opportunity for gusty winds, but confidence is low given quite a bit of uncertainty on the exact storm track. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... Gale Warning from 11 AM EDT /10 AM CDT/ to 8 PM EDT /7 PM CDT/ Friday for LSZ162. Lake Michigan... None. && $$ SHORT TERM...Jablonski LONG TERM...LC AVIATION...Rolfson MARINE...LC