Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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709 FXUS63 KGRR 161610 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 1210 PM EDT Sun Jun 16 2024 .KEY MESSAGES... - Excessive Heat Watch For Most of our Area Monday - Friday - Low Risk for Showers and Isolated Storms Today - Heat and Humidity To Continue Through the Work Week - Much of the Upcoming Week Trending Towards Dry Weather && .UPDATE... Issued at 1024 AM EDT Sun Jun 16 2024 Made adjustments to the POP/Wx grids for today based on current radar trends showing expanding area of convective showers approaching the northern half of the forecast area. Latest Hi Res ARW seems to have the best handle on this initially, so POPs were nudged in the direction with higher POPs extended across the northern half of the forecast area late this morning into the afternoon. Severe threat appears limited by lack of instability, although deep layer shear of about 30 knots may result in some organized linear convection that could bring strong wind gusts. && .DISCUSSION... Issued at 348 AM EDT Sun Jun 16 2024 - Excessive heat watch for most of our area Monday - Friday It will become very hot and humid Monday as upper level ridging strengthens and h8 temps moderate to around 20 C. This in conjunction with southerly flow waa and ample sun with 500mb heights reaching near 590dm will result in high temps reaching the low to mid 90s for much of our area tomorrow. This along with with dew pt values reaching the upper 60s to lower 70s will yield heat indices which will approach the 100 degree mark tomorrow afternoon. Thx for extensive coord on the excessive heat watch headline IWX/DTX/APX. - Low risk for showers and isolated storms today Increasing moisture and an upper disturbance in conjunction with weak instability will result in scattered showers and isolated convection mainly north of the I-96 corridor today as suggested by the 00Z HREF and to some extent our latest CAMs. Otherwise dry wx will prevail for much of the day and it will become hotter with high temps reaching the middle to upper 80s. - Heat and Humidity To Continue Through the Work Week We continue to be concerned with the heat and humidity through the work week and potentially into next weekend as well. We are leaning more on the ECMWF guidance as it has been consistent with the persistent warmth. The GFS has trended warmer with higher 500mb heights with each model run. Evening 850mb temperatures each day this week are between +19C and +21C over GRR. This should yield high temperatures in the lower 90s. When combined with dew points that should be in the upper 60s to around 70 we should have heat index values approaching 100 degrees each day this week. For that reason the Excessive Heat Watch was issued. The cumulative affect of many days of that kind of heat with no relief at night (lows in the 70s) will take its toll, especially on folks without air conditioning. We did not issue for the U.S. 10 row at this point but they may need to be added in as well. Each shift going forward will reevaluate the heat headlines. The current configuration was what we were most comfortable with at this point. Coordinated headlines will all neighboring offices. 500mb heights are impressive with both the GFS and ECMWF showing 590s dm heights the majority of the week. The surface boundary in the ECMWF has trended further northwest in the early to mid week time frame which should keep us more on the sunny side of the ledger. Bottom line, it is going to be a hot and humid week and we will need to check in on folks without air conditioning. People that work outdoors will need to take frequent breaks and drink plenty of water to stay hydrated. - Much of the Upcoming Week Trending Towards Dry Weather Given the high heights and warm mid level temperatures we are becoming less concerned with chances for clouds and precipitation. The one day possibly that we could see precipitation is Thursday as the boundary that was off to our north sags in. The boundary is very much losing definition though and washing out with time as the ridge is dominant. Much if not all the week is looking dry though. Mid summer heat and humidity with little in the way of precipitation is the weather story. && .AVIATION /18Z TAFS THROUGH 18Z MONDAY/... Issued at 1210 PM EDT Sun Jun 16 2024 Clusters of thunderstorms and moderate to heavy rain continue to develop between Muskegon and Milwaukee. Models suggest less instability available with eastward extent into Michigan, which would support a slow weakening trend, so not confident enough yet to include GRR in a TS around 18-19 Z but will do so for MKG. There has been an increase in the number of short-term models which capture the mesoscale convective vortex over northern Missouri to southeast Iowa and thus produce thunderstorms over some of our aerodromes tonight. If this MCV indeed tracks through northern Illinois later today and into southwest Lower Michigan with thunderstorms, storms in our area would be capable of the usual hazards including IFR visibility with heavy rain, lightning, LLWS or 30-45 knot surface wind gusts and wind shifts. Most likely affected would be AZO, BTL, and GRR, and MKG. Will go with VCSH for now but later forecasts may need to narrow down a time frame to add TS at some point between 02 and 12 Z. && .MARINE... Issued at 348 AM EDT Sun Jun 16 2024 A small craft advisory and beach hazards statement is in effect from Grand Haven northward through late tonight. South winds will continue to increase today to near 30 kts at times. This will cause wave heights to build to around 4 to 6 feet from Grand Haven northward. Winds and waves will subside a bit very late tonight and Monday. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Beach Hazards Statement through late tonight for MIZ037-043-050- 056. Excessive Heat Watch from Monday afternoon through Friday evening for MIZ043>046-050>052-056>059-064>067-071>074. MARINE...Small Craft Advisory until 2 AM EDT Monday for LMZ847>849. && $$ UPDATE...Ostuno DISCUSSION...Duke/Laurens AVIATION...CAS MARINE...Laurens