038 FXUS63 KGRR 300728 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 328 AM EDT Fri Jun 30 2023 LATEST UPDATE... Long Term .UPDATE... Issued at 1014 PM EDT Thu Jun 29 2023 Radar trends show the main area of convection across Big Rapids to near Alma, finally moving east and decreasing in intensity. Model trends also support a diminishing trend to the storms. We will continue to feature diminishing POPs through the night. Outflow from those storms has produced a wind shift that made it down to Kalamazoo and Calhoun counties. Visibilities improved behind that wind shift. A southwest flow resumes later tonight and that will likely keep the poor air quality going. && .SHORT TERM...(This evening through Friday night) Issued at 300 PM EDT Thu Jun 29 2023 Shower and thunderstorm chances, along with the persistent smoke, remain the primary forecast challenges. As expected, temperatures warming through the 80s along with dew points inching up through the 60s /to low 70s in some areas/ has resulted in MLCAPES in excess of 1.5k J/kg. In spite of modest instability, an overall weakly forced environment continues to result in uncertainty with respect to storm location/coverage. Very weak front over Wisconsin has made little progress today, and won't pass through the region until Friday. Aloft, quasi- neutral flow is in place, with one embedded ripple currently crossing far northern Michigan as another /MCV/ exiting IA and taking aim on the lower Great Lakes. Expect scattered storms to develop next few hours over parts of Lake Michigan and western Lower Michigan and then push eastnortheastward. Given instability and respectable 500 mb flow aloft, marginally severe wind and hail will be possible with these storms through the evening. By Friday, aforementioned weak front will move across Michigan. It's really more of a modest wind shift than a cold front. In fact, highs on Friday will reach the upper 80s. Still a small risk for scattered convection Friday in presence of continued warmth/moisture and weak boundary, but coverage should remain small and be limited to far eastern and southern parts of forecast area. Lows Friday Night will fall into the 60s, and a small risk for showers/storms will persist mainly along and south of I-94. .LONG TERM...(Saturday night through Thursday) Issued at 328 AM EDT Fri Jun 30 2023 Quasi zonal flow will bring periodic chances of showers and thunderstorms to southwest Lower MI through next week. A decent chance of precipitation exists Saturday night as a short wave move across Illinois and Indiana and southern Lower. Highest PoPs will be south of I-96 Saturday night through Sunday night. The strongest storms with this wave will be south of the cwa in Indiana where the LLJ is strongest and corresponding instability is highest. The next chance of rain after that is likely Wednesday into Friday when a cold front moves into the state. The GFS hints at a wave developing on the front which would prolong the rain threat, which isn't necessarily a bad thing, given the drought status across the region. That said, precipitable water values climb to around 2 inches across the cwa next Thursday, suggesting that storms that develop would be capable of heavy rain. Temperatures will be typical summertime highs in the mid to perhaps upper 80s and lows in the 60s. Humid conditions will also prevail as dewpoints will be in the 60s. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 201 AM EDT Fri Jun 30 2023 An area of showers and thunderstorms have come to an end across Southwest Lower Michigan as of 06z. The remainder of the night will likely be dry with areas of stratus and fog becoming the concern. Status and fog are both likely in the wake of the precipitation. We have IFR conditions developing at most sites with ceilings below 1,000 feet and visibilities possibly dipping to a half mile or less. The fog should burn off fairly quick after daybreak. On a positive note...the smoke has dissipated some with air quality index values being considerably lower as compared to the last few days. VFR weather is forecast Friday afternoon and evening with only a small chance for showers towards LAN and JXN in the afternoon. && .MARINE... Issued at 300 PM EDT Thu Jun 29 2023 Visibility has slowly improved today and the smoke concentrations are expected to diminish on Friday as winds become southwest. Waves will continue to be relatively light into the weekend as winds remain below 20 knots. There could be some locally higher wind gusts in thunderstorms from this evening into the weekend, mostly across areas south of Grand Haven. There could be a push of north winds on Sunday as high pressure builds in. The high is rather weak so winds and waves are not expected to pose a hazard to small craft, although there could some choppy water around Big and Little Sable points. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...None. && $$ UPDATE...MJS SHORT TERM...Smith LONG TERM...04 AVIATION...Duke MARINE...Ostuno