Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 241929
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
330 PM EDT WED AUG 24 2016

LATEST UPDATE...
Synopsis/Short Term/Long Term/Marine

.SYNOPSIS...
Issued at 330 PM EDT Wed Aug 24 2016

A low pressure system moving slowly through the Great Lakes region
will bring scattered showers and a few thunderstorms through
Thursday afternoon. High pressure will build in and bring fair
weather Thursday night through Friday night. The next chance for
showers and thunderstorms will come late Saturday through Sunday.

&&

.SHORT TERM...(This evening through Friday night)
Issued at 330 PM EDT Wed Aug 24 2016

Primary short term fcst concerns involve determining potential for
convection late this afternoon through Thursday afternoon.

18Z mesoscale analysis indicates weak instability over our fcst
area with ml cape values aob 500 j/kg. This is the main reason
convection has not developed and ir sat trends and sfc obs continue
to show rather extensive cloud cover across most of our area.

A few thunderstorms could develop late this afternoon and evening if
more breaks in cloud cover develop allowing instability to increase
a bit. However a consensus of latest short range guidance suggests
much stronger instability will stay well sw to south of our fcst
area.

The vast majority of convection and severe weather will stay south
of our fcst area across portions of IL/IN/OH late this afternoon and
evening. However the chance for showers and a few storms remains in
our fcst overnight though due to forcing from the cold front that
will move into our nw fcst area very late tonight.

The cold front will only very slowly move se across the remainder of
our fcst area Thursday and will bring scattered showers and a few
thunderstorms. The relatively best chc for convection Thursday will
be over our se fcst area given the cold frontal timing. Sb/ml cape
values could potentially reach around 1000 j/kg over toward KJXN
tomorrow aftn prior to fropa. Deep layer shear values are also
favorable at around 40-45 kts.

So a strong to potentially severe storm seems possible over our se
fcst area tomorrow aftn depending largely on the degree of
destabilization prior to fropa. However short range guidance
consensus suggests that greater instability and the primary threat
for severe wx will stay se of our fcst area.

High pressure will build in to produce fair weather Thursday night
through Friday night.

.LONG TERM...(Saturday through Wednesday)
Issued at 330 PM EDT Wed Aug 24 2016

Sfc high retreats to the northeast on Saturday with return flow
moistening and some warm advection showers encroaching on the
western zones in the morning, spreading east in the afternoon. A
weak shortwave trough is damping out as it tops the upper high
centered over the Mid-Atlantic states.

Showers and thunderstorms will be tapering off on Monday, as weak
sfc ridging builds in. Generally zonal flow or flat ridging for
Tuesday and Wednesday with weak impulses moving through and bringing
some isolated showers at times

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 210 PM EDT Wed Aug 24 2016

Ceilings in the 1500 to 2500 ft AGL range will continue this
afternoon along with some isolated showers and thunderstorms.
These conditions are expected to persist overnight with patchy IFR
in showers and thunderstorms becoming more widespread during
Thursday morning. Southwest winds will gust to 20 knots at times
this afternoon.


&&

.MARINE...
Issued at 330 PM EDT Wed Aug 24 2016

A small craft advisory remains in effect from South Haven north to
Manistee through very late tonight. South to southwest winds of 15
to 25 kts will result in wave heights of 3 to 6 feet. The highest
wave heights within that range will be found north of Holland.

&&

.HYDROLOGY...
Issued at 121 PM EDT Wed Aug 24 2016

A Flood Warning remains in effect for the Portage River near
Vicksburg into the weekend. More rain is expected for this area and
river levels will be slow to fall. River levels are above normal
across the area but falling. Additional rainfall may bring levels
near bankfull, but new river flooding is not expected through the
weekend.

&&

.GRR Watches/Warnings/Advisories...
MI...Beach Hazards Statement until 2 AM EDT Thursday for MIZ037-043-
     050-056-064.

LM...Small Craft Advisory until 2 AM EDT Thursday for LMZ845>849.

&&

$$

SYNOPSIS...Laurens
SHORT TERM...Laurens
LONG TERM...Ostuno
AVIATION...Ostuno
HYDROLOGY...63
MARINE...Laurens



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