Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 222241
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
641 PM EDT Sun Apr 22 2018

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 309 PM EDT Sun Apr 22 2018

The warmest day of the week will likely be Monday, with
temperatures climbing to near 70 degrees for the first time in 6
months (except in areas near I-94, which already reached the 70s
on April 12). Temperatures near to below normal then return for
the rest of the week. Rain showers are most probable on Tuesday
and Friday, but amounts will not be particularly heavy.

&&

.SHORT TERM...(This evening through Tuesday night)
Issued at 309 PM EDT Sun Apr 22 2018

Clear skies, dry air, and light east winds will allow temperatures
to fall into the 30s overnight. We will be situated under an
eroding ridge on Monday, separating the cutoff low over Dixie and
an approaching shortwave trough digging through south-central
Canada. Mid/upper level winds will become southerly on Monday,
advecting moisture and developing patches of alto/cirrostratus by
late in the day.

If those clouds remain thin enough for most of the day, many
locations do have a good chance of reaching 70 degrees. 850 mb
temperatures Monday will be 3-4 C warmer than today, so boundary
layer mixing up to that level will make at least upper 60s a good
bet as the ground becomes increasingly dry. East to southeast
surface winds 5-10 mph will keep the lake breeze front close to
the shore especially south of Muskegon, so even those communities
will likely climb into the mid-upper 60s. The NAM and GFS
advertise scattered showers developing in southern Michigan Monday
evening from 850-800 mb moisture, but the potential is low.

As the low to our south becomes reintroduced into the upper-level
westerlies and starts lifting northeast into the Ohio valley on
Tuesday, a cloudy day is expected with a chance of light rain.
Temperatures Tuesday morning will start off fairly mild in the
40s, but highs will struggle to reach 60. Winds from the north
increase Tuesday night with a cold front passing through, dropping
temperatures below normal.

.LONG TERM...(Wednesday through Sunday)
Issued at 309 PM EDT Sun Apr 22 2018

To start the period there are some differences in the models with
regard to the handling of the mid level low east of the
region...but even the westernmost solution keeps the nearly all
the showers east of the CWA. Will forecast a dry day for
Wednesday...but will need to monitor trends on this storms
position in the coming days.

The next storm system will be a mid level wave that digs down from
the northwest Thursday into Friday. The GFS is faster than the
High Res Euro with the precipitation with this system...but even
that solution supports a dry forecast for Thursday...which is what
I will forecast. The moisture deepens up and lift increases with
the wave moving in Thursday night. Forecast soundings from the GFS
could support a rain/snow risk for far northern zones. Will
feature that in the forecast...but confidence is rather low. If
the High Res Euro verifies...there would be no snow up north. We
will have to monitor the temperature forecast for Friday. MOS
guidance from the models has values in the 50s...while GFS
forecast sounding would support 40s. For now will hold values
generally in the 50 to 55 degree range which are well below normal
for this time of the year.

Mid level heights are shown to rise going through the weekend.
This will support a gradual warmup.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 640 PM EDT Sun Apr 22 2018

Clear skies and light winds are expected tonight. The lake breeze
winds will subside by 02z or so (MKG). Monday will see high
clouds overspreading the area, sort of like Saturday. However this
time the clouds will lower and thicken. It would seem MVFR cigs
should be expected by Tuesday morning. Winds will become southeast
Monday around 10 knots.

&&

.MARINE...
Issued at 309 PM EDT Sun Apr 22 2018

Light winds from the east or north through Tuesday will keep waves
low. North winds strengthen Tuesday night into Wednesday, creating
hazardous conditions for small craft.


&&

.FIRE WEATHER...
Issued at 309 PM EDT Sun Apr 22 2018

Sunday afternoon relative humidity 15-25 percent, dry vegetation,
and winds gusting 15-20 mph in some locations have resulted in
elevated fire danger. Winds will decrease and RH will increase
after sunset. Elevated fire wx conditions are again expected
Monday, with RH falling to 25-40 percent.

&&

.HYDROLOGY...
Issued at 309 PM EDT Sun Apr 22 2018

Lowland nuisance flooding near some riverbanks will be ongoing
over the next few days as water from last weekend`s mixed
precipitation event moves through the river basins. Since no heavy
rain events are anticipated in the next week, rivers will
gradually subside.

&&

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

$$

SYNOPSIS...CAS
SHORT TERM...CAS
LONG TERM...MJS
AVIATION...WDM
FIRE WEATHER...CAS
HYDROLOGY...CAS
MARINE...CAS



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