958
FXUS63 KGRR 161424
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1024 AM 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 /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 758 AM EDT Sun Jun 16 2024

VFR weather is in place across Southwest Lower Michigan at 12Z,
while showers and thunderstorms are moving east across Wisconsin.
The question is how much if any of this activity makes it into our
area later this morning and afternoon. Our feeling at this point
is much of if not all of the activity will remain northwest of the
TAF sites today. The clouds today will be of the mid and high
variety with bases at or above 8,000 feet for the most part.

Tonight we may see some shower and thunderstorm activity spill
into Central Lower Michigan from the north, but this will also
largely miss the TAF sites.

Winds today will be gusty out of the south at 15 to 25 knots.

&&

.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...Duke
MARINE...Laurens

NWS GRR Office Area Forecast Discussion