Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 241756
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
156 PM EDT SUN JUL 24 2016

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 253 AM EDT Sun Jul 24 2016

An area of low pressure will track through the Great Lakes region
today and tonight resulting in showers and thunderstorms at
times. High pressure will move in behind the departing system for
Monday and Tuesday. This will result in a return to the dry
weather. Overall the temperature will remain above normal into the
middle part of the week.

&&

.UPDATE...
Issued at 1100 AM EDT Sun Jul 24 2016

At 15Z KGRR radar trends continue to show a large area of rain and
scattered convection across most of our fcst area. Convection
earlier this morning only produced gusts in the 30 to 40 mph range
and no severe reports. Sfc based instability is weak given
extensive cloud cover and showers.

A small area of strong convection west of Ludington and Pentwater
will continue to move east and will produce frequent lightning...
brief heavy rain and perhaps some small hail and strong wind gusts
as it moves onshore in the next hour. This convection will affect
areas mainly near to north of a line from Pentwater to Mt.
Pleasant during the next 1-3 hours.

We expect scattered showers and a few thunderstorms to continue
to develop this afternoon given strong 1000-850 mb moisture
transport and decent elevated instability. However outside of
strong to marginally severe cells west of KLDM attm the severe
weather threat this afternoon looks low and very marginal given
extensive cloud cover and very little sfc based instability.
Stronger storms will continue to bring heavy rain with
precipitable water values way up in the 2-2.25 inch range and
strong 1000-850 mb moisture transport.

&&

.SHORT TERM...(Today through Tuesday)
Issued at 253 AM EDT Sun Jul 24 2016

The main change to the forecast was to increase pops today. One
MCS was track through Southern Lower Michigan at this time. This
will result in increase rainfall for places like
Kalamazoo...Battle Creek and Jackson. Meanwhile a southwesterly
low level jet was pushing through WI. This feature will advect in
abundant moisture as it pushes through Southwest Lower Michigan
this morning. So it appears that the convection upstream of
Muskegon will fill in as it approaches. A small risk for severe
this morning...but instability is somewhat limited.

Depending on how much sun we see for the remainder of the day will
largely determine how much if any strong to severe storms we see
later today. The mid to upper level wave moves in the the cold
front pushing down from the northwest. There is clearing out ahead
of this feature in parts of WI and MN that should track into
Southwest Lower Michigan today. Based on developing instability
and increasing shear...there appears to be a risk for a few severe
storms this afternoon or evening.

.LONG TERM...(Tuesday night through Saturday)
Issued at 253 AM EDT Sun Jul 24 2016

Tuesday night looks dry with zonal flow in the upper levels and
ridging/weak flow still in place in the low and mid levels of the
atmosphere. Rain chances increase on Wednesday as both the ECMWF and
GFS show a shortwave approaching from the Upper Midwest. The GFS
features a stronger wave persisting a bit longer into Thursday, but
there is consensus on broad, longwave troughiness late in the week.

Rain and thunderstorm chances will be highest Thursday into Friday
with the surface low moving through the region, but it`s still much
too early to try to get more precise with the timing of convection.
High temperatures will gradually fall from the mid-upper 80s on
Wednesday to the lower 80s for Friday and Saturday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 156 PM EDT Sun Jul 24 2016

Early morning convection has progressed into Southern Lower
Michigan and weakened. A broken like of storms stretches across
Central Lower Michigan and may become the focus for additional
develop this afternoon.

The level instability is in question with early morning rainfall
and leftover cloud cover. Therefore, VCTS has remained in the TAFS
for all sites this afternoon with occasional gusts near 20kts
possible. CIGS and VSBYS should remain in VFR territory for a
large portion of the time with exception to any thunderstorm
affected sites. This will have to be adjusted accordingly if
development become more widespread.

Once the front move through the main concern tonight is the
potential for fog. I remained optimistic with most locations
staying MVFR. Southern sites seem to have the best potential to
dip into IFR momentarily before sunrise. Conditions should quickly
improved going into Monday with lifting CIGS and clearing skies.

Once the front moves through

&&

.MARINE...
Issued at 253 AM EDT Sun Jul 24 2016

Will go ahead and issue a Small Craft Advisory and Beach Hazards
for part of today. A low level jet will move in this morning. Thus
the wind will increase. The longer fetch supports the region north
of Muskegon. Will need to monitor areas further south as well. The
convection this morning could alter/enhance the setup...so its not
certain to happen.


&&

.HYDROLOGY...
Issued at 1250 PM EDT Sun Jul 24 2016

No river flooding is expected through next week. Area wide rain of
around an inch with locally up to 3 inches (mainly near Lake
Michigan) has fallen since Saturday evening. Another wave of showers
and storms are possible tonight. A small chance of rain is also in
the forecast Wednesday through Friday. River levels are at or below
normal for this time of year, so this rain should not bring any
rivers to flood.

Strong thunderstorms could produce localized rainfall totals over an
inch and lead to localized ponding of water. Rainfall totals will
probably vary substantially over short distances.

&&

.GRR Watches/Warnings/Advisories...
MI...Beach Hazards Statement until 5 PM EDT this afternoon for MIZ037-
     043-050.

LM...Small Craft Advisory until 5 PM EDT this afternoon for
     LMZ847>849.

&&

$$

UPDATE...Laurens
SYNOPSIS...MJS
SHORT TERM...MJS
LONG TERM...EBW
AVIATION...JAM
HYDROLOGY...63
MARINE...MJS



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