Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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775 FXUS63 KMQT 280845 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 445 AM EDT Sun Apr 28 2024 .KEY MESSAGES... - Much cooler today with showers lifting from south to north during the afternoon. - Active pattern continues as three low pressure systems track across the region over the next week. Above normal temps/precip are expected including thunderstorm chances. && .SHORT TERM /THROUGH THIS AFTERNOON/... Issued at 328 AM EDT Sun Apr 28 2024 Water vapor imagery and RAP analysis show that the shortwave that affected Upper MI yesterday is now e and ne of Lake Superior. The next shortwave has lifted out of the southern Rockies and out over the western Plains. This wave is supporting a long band of convection from TX to eastern KS, then to northern IL/IN. Frontal boundary associated with the former wave is supporting additional convection across central Lwr MI with even a few -shra back to near Menominee. Across Upper MI, sfc winds are in the process of veering n to ne in response to sfc high pres building into northern Ontario and low pres over s central KS. In this veering upslope flow, some -dz has developed into portions of western and n central Upper MI. This -dz may linger for another couple of hrs. Under cloudy skies, temps at 07z mostly range thru the 40s F, but it`s still in the low 50s at Menominee, and upper 30s are becoming more common across the w to n central. Today will be a much cooler day than yesterday under ne winds btwn high pres building over northern Ontario and low pres lifting to IA. Many locations will have high temps 15-25F lwr than yesterday. Under generally cloudy skies, expect high temps today around 40 to the mid 40s w to n central ranging up to the low/mid 50s e. As low pres lifts to IA today, strengthening waa/isentropic ascent will spread into the Upper Great Lakes along with a nice push of 850-700mb moisture transport. In addition, sharpening 850mb warm front will approach. End result will be an organizing area of shra that will lift n out of WI into Upper MI this aftn. Consensus of recent guidance suggests -shra should reach Menominee County early aftn and then slowly/steadily lift n during the aftn, though there is uncertainly in how far n pcpn will get before 00z. While no pcpn will reach the Keweenaw thru 00z, there is uncertainty across the rest of northern Upper MI. It`s possible areas from Ontonagon to L`anse, Marquette and Munising/Grand Marais will remain dry thru 00z as well, but there is sufficient support for at least a 20-50pct chc mention in those areas 22-24z. && .LONG TERM /TONIGHT THROUGH SATURDAY/... Issued at 443 AM EDT Sun Apr 28 2024 Not much about the extended period forecast has changed with good model agreement in three low pressure systems tracking across the region over the next week. While this is a very active pattern with frequent rain chances, overall weather impacts are expected to be minor. Thunderstorm chances represent the primary hazard with gusty winds and locally heavy rainfall representing the secondary hazards. The first system will be on our doorstep tonight and its warm front will be the primary mechanism focusing rain chances. There are some noteworthy model differences with rain chances along this warm front. Most deterministic guidance appears to focus the heaviest rain near the nose of a 40-45 kt LLJ between 00-06z Monday. This keeps most rainfall near the Lake MI until early Monday morning, when the warm front surges across the area. ECMWF guidance seems to be an outlier with a more coherent warm front passage and PoPs were adjusted to better represent potential for two waves of rain tonight. Steadier rain lifts northeast of the area by midday and the cold front sweeps across the area during the afternoon, but persistent low level cloudiness prevents much destabilization. HREF means indicate MUCAPE values stay less than 100 J/kg until Monday afternoon suggesting thunder/lightning will be tough to achieve tonight, but may accompany afternoon showers. Pwats of 1-1.25 inches indicates some potential for heavy rainfall rates, but prolonged dry conditions suggests hydro hazards are unlikely. Rain chances end behind the cold front leading to a ~36 hour period of dry weather ahead of the next system. The next system approaches Tuesday evening and substantial model differences exist. The general model consensus is for an energetic and negatively tilted shortwave pivoting across the area Tuesday night. The dominant surface low stays well to our northwest across the Canadian Prairies such that the warm sector briefly tracks across Upper MI. Most model guidance keeps the warm front dry while focusing convection along the cold front. The nocturnal timing of this cold front is not favorable for convection in our area, but upper level forcing may be sufficient to compensate for that. Ensemble means indicate a northwest to southeast precipitation gradient with highest amounts across the far west and Copper Country. Model spread remains large on Wednesday, but a ~1000 mb surface low should be in the vicinity of Lake Nipigon Wednesday afternoon. Moderate westerly flow south of the low is expected to result in a dry and breezy day with deep mixing. EPS peak gust guidance shows slightly higher winds over land indicating surface heating is important for efficiently low level mixing. At this time westerly gusts in the 30-40 mph range are forecast across the west half, highest on the Keweenaw where about 20% of EPS members have peak gusts >50 mph. It should be noted that other model suites have considerably weaker winds on Wednesday, but zonal flow south of the surface low tends to result in deep mixing. In addition to gusty winds, deep mixing also indicates potential for RH to dip below currently forecast values but recent rainfall should keep fire wx concerns in check. Medium range guidance has trended toward another low pressure tracking into the region to close out the work week. Rain chances increase on Thursday as the system approaches before ending on Friday as the system departs. Embedded thunderstorms once again appear possible. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 126 AM EDT Sun Apr 28 2024 Medium to high confidence in IFR at IWD with persistent upsloping early in the northerly winds behind departing low pressure system. Confidence is low, however, in MVFR conditions continuing at CMX and SAW through this morning, so will carry a mention of IFR. Anticipate much fluctuation through the morning hours though overall with increasing confidence in MVFR becoming predominant by early afternoon. Northeasterly winds will increase this afternoon at IWD/SAW followed by CMX this evening, gusts in excess of 30 kts possible. && .MARINE... Issued at 443 AM EDT Sun Apr 28 2024 Generally north winds gusting between 15 and 25 knots are occurring early this morning across Lake Superior. Winds back northeasterly early this morning as a low pressure approaches. Northeast gales up to 40 kt are expected across the far western lake this afternoon with easterly gales to 40 kts spreading across the entire lake tonight. While a few gusts may exceed 40 kts late tonight into Monday, probabilities remain on the low end (25-50%). The strongest winds are expected in the far west as well as the north central portion of the lake between the Keweenaw and Isle Royale where there could be some channeling. Gales quickly diminish Monday afternoon as the low pressure moves over western Lake Superior. Significant wave heights up to 14 ft are possible Monday morning between Duluth Harbor to the Bayfield Peninsula and near Isle Royale. Waves fall below 8 ft Monday evening. Winds fall below 20 kts Monday night, mainly remaining below until Wednesday morning. West winds increase to around 30 kts with a few gale force gusts to 35 knots possible between Isle Royale and the Keweenaw Peninsula Wednesday afternoon. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... Gale Warning from 2 PM EDT /1 PM CDT/ this afternoon to 5 PM EDT /4 PM CDT/ Monday for LSZ162. Small Craft Advisory until 8 PM EDT /7 PM CDT/ Monday for LSZ240-241. Small Craft Advisory until 7 PM EDT Monday for LSZ242. Small Craft Advisory until 11 PM EDT this evening for LSZ243>245. Gale Warning from 11 PM this evening to 5 PM EDT Monday for LSZ243>246-263>266. Small Craft Advisory from 11 AM this morning to 11 PM EDT this evening for LSZ246. Small Craft Advisory until 8 PM EDT Monday for LSZ247-248. Small Craft Advisory until 5 PM EDT Monday for LSZ249>251. Lake Michigan... Small Craft Advisory from 6 PM this evening to 11 AM EDT Monday for LMZ221. Small Craft Advisory from 6 PM this evening to 4 PM EDT Monday for LMZ248-250. && $$ SHORT TERM...Rolfson LONG TERM...EK AVIATION...TDUD MARINE...EK