Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 230001
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
801 PM EDT FRI JUL 22 2016

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 328 PM EDT Fri Jul 22 2016

The hot and humid weather will continue into Sunday before a cold
front comes through and brings relatively cooler and drier air
into the area. That relativity cooler air will last through next
week. The next chance for thunderstorms will be Sunday into Sunday
night. If your area misses out on that rain, the next chance would
be Wednesday into Thursday.

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 328 PM EDT Fri Jul 22 2016

The main issues are the threat of thunderstorms on Sunday and just
how hot it will get Saturday. It does not look like we will have
high enough dew points to justify a heat advisory Saturday.

The passage of weak cold front through the area has brought much
drier mid level air into the area (as seen on the water vapor
image loops). A Canadian shortwave passing well north of the area
is helping to bring down the drier air. This dry air will prevail
over the area into Saturday evening. That will keep the chance for
thunderstorms below 10 pct through early evening Saturday.

That dry air will also allow for cooler lows tonight, with most
areas having lows in the 60s. On Saturday we do have a surge of
hot air later in the day. That should help bring our highs into
the lower to mid 90s. With dew points in the 60s, that will not be
hot enough for a heat advisory.

Our next chance for thunderstorms will be Sunday into Sunday
night. A northern stream system will push a warm front through the
area in the morning. That will bring the risk of thunderstorms.
Then the cold front will come through Sunday evening and that will
also have the threat for thunderstorms. There is good moisture for
this system but the best dynamics are north of the area once
again. On the up side, we do get the right entrance region of the
polar jet Sunday evening. That could help the cause of bringing
much needed rain to the area once again. The severe risk looks
marginal at best.

.LONG TERM...(Monday through Friday)
Issued at 328 PM EDT Fri Jul 22 2016

The beginning of the upcoming work week looks to be dry with surface
high pressure in place much of the time. A cold front will be
slipping off to the east of the area Monday morning with the high
centered overhead on Tuesday. Have a dry forecast in place for
Monday through Tuesday night. 850mb temps are still fairly warm on
Monday, so looking at highs well into the 80s despite the frontal
passage. 850mb temps do not change much into Tuesday either, so a
similar warm story that day as well.

Have small chances for showers and thunderstorms the remainder of
the week, from Wednesday through Friday. Wednesday and Wednesday
night a low pressure system will be traversing the area and these
periods are probably the best chances for rain in the long term. The
flow is fairly zonal with a shortwave swinging through the Great
Lakes.

Thursday into Friday the upper flow is more northwesterly with
another shortwave embedded in the flow. Moisture is a bit more
shallow in these periods, but cannot rule out some precipitation.
Temperatures should be closer to normal on Thursday and Friday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 800 PM EDT Fri Jul 22 2016

The main issue is the fog potential later tonight with clear
skies and calm sfc winds expected. Dew pts are currently 65 to 70
and may actually come up a couple degrees once diurnal
mixing/daytime heating ceases.

With crossover temperatures in the mid to upr 60s and fcst low
temperatures about the same, believe we will at least see some
MVFR fog and a small possibility of IFR/LIFR fog... mainly 07z-
12z. The fog will lift/burn off abruptly Saturday morning leaving
VFR conditions for the rest of the day.

&&

.MARINE...
Issued at 328 PM EDT Fri Jul 22 2016

We will likely need a small craft advisory Sunday as we get into
the warm sector of the system moving through the area. Likely a
beach hazard statement will be needed too.


&&

.HYDROLOGY...
Issued at 1233 PM EDT Fri Jul 22 2016

Thursday rainfall amounts ranged from a tenth to three-quarters of
an inch across the whole area... a welcome sight for many.
Sunday`s thunderstorms will likely produce a similar range of
amounts, although locally higher amounts could occur if the storm
mode turns out to be more of a multicell cluster rather than
progressive linear like Thursday.

&&

.GRR Watches/Warnings/Advisories...
MI...None.
LM...None.
&&

$$

SYNOPSIS...WDM
SHORT TERM...WDM
LONG TERM...Duke
AVIATION...Meade
HYDROLOGY...CAS
MARINE...WDM



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