607
FXUS63 KGRR 021130
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
730 AM EDT Sun Jun 2 2024

.KEY MESSAGES...

- Limited chance of showers today through Monday afternoon

- Medium/High Confidence in evolution of upper troughing this week

&&

.DISCUSSION...
Issued at 312 AM EDT Sun Jun 2 2024

- Limited chance of showers today through Monday afternoon

Weak surface low pressure over central lower Michigan early this
morning will shuffle east today. Moisture and clouds in the mid to
upper levels will depart but remain in the low levels for some
portion of the day. Areas of light drizzle may linger this morning
over the middle of lower Michigan. Question will be how quickly does
the low stratus mix and scatter into diurnal cumulus. Latest
guidance more aggressive with sunshine this afternoon near/west of
US-131, while some models including the HRRR leave areas near I-69
relatively gloomy where low level wind convergence and troughing
hangs around a little longer on the backside of the low. Will keep
about a 10 percent chance of measurable rainfall there this
afternoon.

Near-normal temperatures today trend seasonably warm on Monday,
while humidity will be a little more noticeable (dew points near
60). Upper level flow over the northern CONUS through Monday is
fairly zonal but weak, with the next shortwave trough of note
approaching Michigan late Monday. Cirro/alto clouds will be
streaming in on Monday from upstream thunderstorms. The chance of
showers and thunderstorms appears low until late in the day when
better 850 mb moisture streams in and instability increases.

- Medium/High Confidence in evolution of upper troughing this week

Shortwave ridging early this week gives way to height falls by
Tuesday as a closed upper low approaches from the northwest. This low
figures in the evolution of persistent troughing across the Great
Lakes by the end of the week with lower 500 mb heights and low level
northwest flow indicating cooler than normal temperatures into next
weekend.

As far as rain chances, they persist from Monday night through
Wednesday in most southerly flow ahead of the upper low and should
peak on Monday night as a shortwave trough minors out and again
Tuesday night into Wednesday as a cold front will focus rain and
embedded thunderstorms. Showery and cool under the upper low for
late week and the weekend.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 728 AM EDT Sun Jun 2 2024

Areas of IFR and patchy LIFR will improve to MVFR this morning
and to VFR this afternoon. Winds will go northwest behind the
cold front this morning but remain AOB 10 knots.

&&

.MARINE...
Issued at 312 AM EDT Sun Jun 2 2024

Limited potential for hazardous conditions in the nearshore Lake
Michigan waters today and during the day Monday. Some patches of fog
may be present this morning. Winds will be from the northwest and
light today, and a little breezier from the south on Monday.
Thunderstorms may occur over the water between Monday evening and
Wednesday.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.

&&

$$

DISCUSSION...Ostuno/CAS
AVIATION...Ostuno
MARINE...CAS