textproduct: Grand Rapids

KEY MESSAGES

- Slight Risk for Severe Storms Today

- Slight Risk for Severe Storms on Tuesday

- Drier and cooler mid to late week

DISCUSSION

Issued at 400 AM EDT Mon May 18 2026

- Slight Risk for Severe Storms Today

The storm prediction center has placed Southwest Lower Michigan in a slight risk for severe weather today. Clouds and showers will try to press in from the west this morning which will decrease somewhat how much we can destabilize. 500mb flow will be weakening as we move through the day as well which is another negative factor with regard to severe weather chances. What we are watching though is the chance that the current activity redevelops or regenerates over our area after about noon (this is seen in the HREF). We feel that between roughly 100pm and 700pm there is chance for severe weather, especially south and east of a line from Whitehall to Clare (so the bulk of the area). An item of note in the HREF is the 850mb low level jet ramps up during the afternoon to 40-45 knots. The LLJ increase is seen most for areas near and southeast of GRR including AZO, LAN and JXN. These areas stand the best chance at some damaging winds this afternoon and evening. The Nadocast machine learning website also sees wind as our biggest threat today over our southeast half of the forecast area. There is a chance for some scattered storms tonight, but nothing that looks widespread.

- Slight Risk for Severe Storms on Tuesday

Another slight risk for severe storms is in place for Tuesday over the southeast CWA. The setup is similar in that decaying showers and storms will move in during the morning with a threat of redevelopment over our area in the afternoon. Tomorrow's threat though looks more confined to the southeast CWA, essentially a smaller threat area including AZO, LAN and JXN. Today we have some threat outside of those areas, but tomorrow (Tuesday) the best chances may very much be confined to those areas. Deep layer shear on Monday is 25-35 knots and Tuesday that increases to 30-40 knots. So some storm organization is possible especially with Tuesday's threat. Again though, the morning clouds and showers may dampen our threat a bit.

- Drier and cooler mid to late week

The cold front will sweep through the forecast area Tuesday evening. Much drier air will invade from the north with PWAT values plummeting from 1.7 inches Tuesday morning which is off the chart for this time of year to less than 0.5 inches on Wednesday. It will be noticeably cooler with highs in the 60s Wednesday and Thursday. Wednesday night we are likely looking at frost across Central Lower Michigan.

Another systems looks to bring some rain out towards Friday, but the models have had difficulty coming to a consensus. The trend though looks to be towards rain on Friday.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

Issued at 647 AM EDT Mon May 18 2026

Very little change in thinking from overnight. We are expecting a broken line of showers and thunderstorms to move into Western Lower Michigan between 14z and 17z. These will largely be in a weak state. Re-intensification will take place around 17z however with a line of showers and storms then expected to push eastward through the TAF sites. Have VCTS in the TAFs now, but we expect at least scattered activity to affect the TAF sites between 17z and 23z. All sites will largely stay VFR today outside of some brief reductions in visibility and ceiling associated with a storm affecting any one TAF site.

Winds will ramp up considerably in the next hour or two (or by 13z to 14z), with SSW winds from 190-210 running at 15-30 knots much of the day.

MARINE

Issued at 400 AM EDT Mon May 18 2026

We have extended the Small Craft Advisory both in time and areal extent. The SCA now runs through Tuesday for all zone. The southern two zones, south of Holland, begin tonight. Strong southerly winds will continue both today and Tuesday as we remain east of the cold front the bulk of that time. South winds of 15 to 25 knots look common with waves of 3 to 6 feet. The SCA may need to be extended into Tuesday night for a period of stronger northwest winds behind the cold frontal passage.

GRR WATCHES/WARNINGS/ADVISORIES

MI...None. MARINE...Small Craft Advisory from 2 AM to 8 PM EDT Tuesday for LMZ844- 845. Small Craft Advisory until 8 PM EDT Tuesday for LMZ846>849.