Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 252343
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
743 PM EDT Wed May 25 2022

LATEST UPDATE...
Aviation

.DISCUSSION...(This evening through next Wednesday)
Issued at 252 PM EDT Wed May 25 2022

...Marginal Risk Severe Southwest this Evening...

Still no clear signal upstream that organized convection will be
initiated this afternoon as warm advection is rather broad with no
clearly defined warm front to focus on. Breaks in the clouds
across central Indiana should help the cause with model guidance
showing instability increasing by late afternoon into northern
Indiana, although the gradient of higher instability remains just
south of our forecast area.

The specifics are still murky on timing of any convection moving
into southern Lower Michigan as the FV3 and ARW differ on the
near term evolution of convection. At this point based on current
radar trends and instability gradient it appears more likely the
later timing of the FV3 will verify, with the best chance for
storms after 6 pm. The main threat is isolated wind damage
including transient weak tornadoes. Instability wanes after 9 pm
although storms could persist through 11 pm.

...Marginal Risk Severe Thursday...

The surface low slowly advances northeast along the stalled front
and surface convergence is greatest at the time of higher diurnal
instability across the southeast zones in the late
afternoon/early evening which should initiate areas of
thunderstorms.

Wind profiles show about 25 to 30 knots of shear with limited CAPE,
which is very tall across the southeast zones but also very
"skinny". Any updrafts in this area appear capable of isolated wind
damage. Low to mid level shear profiles are unidirectional so the
tornado threat appears to be low.

Precipitable water is around 1.5 inches on Thursday and MBE
vectors show storm motion 10 knots or less in the vicinity of the
front, so some minor flooding is also possible.

...Fair Weather Weekend with Rising Heights...

Cold front pushes through Friday with rain and some embedded thunder
persisting along and ahead of the front into the evening before
ending from northwest to southeast. Fair weather for Saturday and
beyond as a big upper low digs in over the Rockies, building an
upstream ridge/closed upper high downstream across the Midwest with
temperatures climbing by to the 80s Monday through Wednesday before
the western CONUS trough moves east.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 743 PM EDT Wed May 25 2022

Areas of MVFR and isolated IFR conditions in showers and
thunderstorms can be expected through Thursday afternoon.
Coverage of storms will decrease this evening as instability
decreases then increase again as low pressure moves through on
Thursday.

LLWS is expected this evening with 40 to 45 knots at 2 kft AGL.
Surface winds will gust over 20 knots at times with isolated
higher gusts in thunderstorms.

&&

.MARINE...
Issued at 252 PM EDT Wed May 25 2022

Offshore winds will gust to 30 knots at times through tonight
with waves building to near 5 feet well offshore. Winds and waves
will diminish on Thursday afternoon and remain relatively light
into the weekend before south winds increase to 20 knots on
Sunday.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 5 PM EDT Thursday for LMZ845>849.

&&

$$

DISCUSSION...Ostuno
AVIATION...Ostuno
MARINE...Ostuno


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