National Weather Service Raw Text Product

Displaying AFOS PIL: AFDGRR Received: 2020-07-14 23:24 UTC


927 
FXUS63 KGRR 142324
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
724 PM EDT Tue Jul 14 2020

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 330 PM EDT Tue Jul 14 2020

- Showers and Storms possible overnight across West Central Lower
  Michigan

- Lull in the activity on Wednesday 

- Showers and Storms likely Wednesday night

- Drying out Thursday into Friday

- Warmer with showers and storms over the weekend

&&

.DISCUSSION...(This evening through next Tuesday)
Issued at 241 PM EDT Tue Jul 14 2020

-- Showers and Storms possible overnight across West Central 
   Lower Michigan --

Showers and a few thunderstorms are possible tonight across West
Central Lower Michigan as a weakening frontal boundary moves
towards the area. 850mb LI's drop to around -4C which is
associated with the LLJ/surge of low level moisture. Not expecting
anything heavy tonight, more on the order of a quarter inch or
less.  

-- Lull in the activity on Wednesday --

A lull in the showers and storms is expected on Wednesday for the
bulk of the area. Showers will continue across West Central Lower
up towards Ludington, but the bulk of the area will see dry
conditions or only isolated/scattered showers. Highs on Wednesday
should surge well into the 80s.

-- Showers and Storms likely Wednesday night --

The most likely time frame for precipitation in the next 5 days or
so will come Wednesday night when a mid level wave will push
directly through the area. Models are still deepening a surface
low through the area, but overall its on the weaker side. Models
also still show a solid 850mb low level jet sliding from west to
east across Southern Lower Michigan. We are expecting a round of
showers/storms Wednesday night. Locally heavy rain is certainly
possible with some showing a swath of 1-3 inches across the
Muskegon river basin. The better bet is that we see some heavier
totals in the south along the I-94 corridor. Given high surface
dew points, a low level jet and a boundary to interact with not
out of the question to see some brief localized ponding of water.
We are not expecting widespread areal or river flooding. Severe
weather threat looks low given marginal instability. Cannot rule
out some localized wind gusts to 40-50 mph, but that would be
about it. 

-- Drying out Thursday into Friday --

The flow trends zonal aloft for the end of the week and into the
weekend. We look dry from Thursday afternoon through Friday night.

-- Warmer with showers and storms over the weekend --

The heat still looks like it comes in for the weekend with 850mb
temps climbing to 19C to 22C. This should yield temperatures into
the 90s. The caveat however is there may be precipitation around
as well as clouds given a boundary sagging into the area. The
weekend will not be a wash out by any means, but we have pops in
the forecast for every 6 hour period from Saturday through Sunday
night. 

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 724 PM EDT Tue Jul 14 2020

VFR conditions will continue into Wednesday afternoon. MVFR
conditions could begin moving into western Lower Michigan by late
afternoon as showers and thunderstorms spread east. The higher
chances of this will be towards MKG and AZO after 20Z. Winds will
be southwest AOB 10 knots.

&&

.MARINE...
Issued at 330 PM EDT Tue Jul 14 2020

Still a bit concerned about the wind in the profile tonight over
Lake Michigan with regard to possible Small Craft Advisory
conditions. Will not issue a headline tonight though, but we will
be monitoring. Winds around 1,000ft increase to 25 knots from the
southwest overnight. Our feeling is that the higher winds are
fairly short lived in our forecast area, on the order of 6 hours.
Also, the wind may not mix to the lake surface efficiently given
the upwelling that has occurred which probably sets up a low level
inversion inhibiting mixing to the lake surface.

There may be another short lived marginal Small Craft event on
Wednesday night where winds and waves will come up briefly out of
the north as a deepening low passes through the Southern Great
Lakes. It appears the highest winds and waves will occur across
the south end and especially offshore. 


&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&

$$

SYNOPSIS...Duke
DISCUSSION...Duke
AVIATION...Ostuno
MARINE...Duke