000
FXUS63 KGRR 281734
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
134 PM EDT Thu May 28 2020
LATEST UPDATE...
Aviation
.SYNOPSIS...
Issued at 330 AM EDT Thu May 28 2020
- Showers and thunderstorms into tonight
- Lingering showers Friday and cooler
- Much cooler this weekend
- Next system mid next week brings convection back
&&
.DISCUSSION...(Today through next Wednesday)
Issued at 330 AM EDT Thu May 28 2020
-- Showers and thunderstorms into tonight --
Today will not be a lot different than yesterday in terms of
afternoon and evening convection. However I do not think the
convection that is there today will be as vigorous as the past 2
days have been. Precipitable water values are up near 1.5 inches.
Model sounding are rather moist all the way up today into tonight.
So it does look like locally heavy rainfall once again. The HREF
6hr PMM (probability matched mean) shows similar rainfall for this
afternoon, as it did yesterday for yesterday afternoon, and
mostly the similar places.
However the severe threat is less today than the past 2 days. The
model sounding as mentioned above do look rather saturated so
downdraft capes are significantly lower than the past 2 days. Also
due to the incoming upper wave, heights lower and so do thickness
values which means the air will not be as warm , plus with all of
that mid level moisture it should be more of a mostly cloudy sky
too. Which means less instability. Less instability is shown by
numerous models and model sounding today as well as the SPC SREF.
The SREF 3 hour calibrated probability of severe storms never
gets to more than 2 percent and that is only over our extreme
southwest CWA during the late afternoon. Since the soundings are
so moist, the only risk would be for gusty winds since there is
not enough cape in the mid levels for hail. Downdraft capes are
less than 500 j/kg so that threat is rather low today actually.
The convection associated with the shortwave ahead of the cold
front comes through this evening but instability falls
considerably after midnight. I wounder if there will even be
enough instability for thunderstorms. The greatest threat for
thunderstorms today is mid afternoon into mid evening. That is
also the time with the greatest threat for heavy rainfall.
-- Lingering showers Friday and cooler --
There is a threat of showers into Friday morning but once the
upper trough moves into the area by midday, skies should clear and
will not be nearly as warm.
-- Much cooler this weekend --
A deep upper trough digs into the Great Lakes this weekend and the
southern stream jet core will be south of Michigan. We will be
rather chilly with frost not out of the question near route 10
Saturday and Sunday morning. Highs should only get into the 60s
both days.
-- Next system mid next week brings convection back --
A Pacific shortwave moves through the pattern in the Tuesday to
Wednesday time frame. This brings back warmer air and convection.
Hard to say this far out how this will play out but it could be
another wet pattern.
&&
.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 130 PM EDT Thu May 28 2020
Occasional reductions in cigs and visibility are possible as
showers and a few thunderstorms develop this afternoon and
evening. These reductions can go into IFR fairly quickly but may
not last more than 30 minutes or an hour at any one point. The
more likely timeframe for IFR looks to be late tonight and early
Friday morning as a cold front approaches. Ceilings may be IFR at
any point from 04z-12z Friday especially.
&&
.MARINE...
Issued at 330 AM EDT Thu May 28 2020
Not to much in the way of Marine hazards at this point expect for
thunderstorms this afternoon and evening and possibly some patchy
fog.
&&
.HYDROLOGY...
Issued at 330 AM EDT Thu May 28 2020
The Grand River at Comstock Park and Robinson Township continues
to fall and should fall below flood stage today. However, any
substantial rainfall from today and tomorrows storms could slow
the descent and the fall below flood stage may be delayed.
Heavy rainfall today will be localized however there could be
brief rises in creeks, streams and urban areas may see localized
flooding today as there was yesterday.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&
$$
SYNOPSIS...WDM
DISCUSSION...WDM
AVIATION...Hoving
HYDROLOGY...WDM
MARINE...WDM
NWS GRR Office Area Forecast Discussion
