Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 220729
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
329 AM EDT Sat Apr 22 2017

LATEST UPDATE...
Synopsis/Short Term/Long Term/Marine

.SYNOPSIS...
Issued at 309 AM EDT Sat Apr 22 2017

A large area of high pressure located in the Upper Plains will
track slowly eastward into the Great Lakes Region through the
weekend. This fair weather system will act to keep it dry.
A weak cold front will try to slip down from the north Sunday
night...but this feature is expected to diminish as it moves in.
A better shot for rain arrives for the middle part of the week
when a low pressure system tracks in from the southwest.

&&

.SHORT TERM...(Today through Monday)
Issued at 309 AM EDT Sat Apr 22 2017

Models are in relative agreement in tracking a high pressure
system in from the west through the weekend. The main issue
appears to be frost. Overall it looks like somewhat of a higher
risk tonight. This is because the cloud cover will be less and
with lighter winds. So...I added patchy frost to the for the
region tonight.

A weak backdoor cold front slips down from the north Sunday night.
At this time no precipitation is forecasted as this system will be
weakening...feature little or no lift and the atmosphere will
remain dry.



.LONG TERM...(Monday night through Friday)
Issued at 309 AM EDT Sat Apr 22 2017

A busy weather pattern returns to the region by mid-week with
several waves of precipitation possible through the end of the week.
A couple of these events could include heavy rain and stronger
thunderstorms.

High pressure will continue to exit east Monday night. The zonal
pattern begins to erode with southwest flow advecting warmer air
into Lower Michigan through the day Tuesday.

The first wave will be surface low that was originally expected to
arrive into the area Tuesday night. This system continues to shift
northwest in the latest guidance. Better dynamics stay west of Lower
Michigan until at least Wednesday, when a cold front tries to push
eastward. There are some timing differences between two models as we
go through the day. Forecast soundings point to a unidirectional
flow regime, which would suggest a linear pattern to storm mode.
Timing could make a big difference if storms could tap into any
afternoon instability. ECM guidance is much slower at pushing the
front through with a more south-to-north track in surface low, which
could keep rain in the forecast through early Thursday.

The second wave moves in Friday with much less confidence on
placement. Both the ECM/GFS diverge with solutions spreading
somewhere between Iowa and Ohio. This system will be patterned with
a much strong upper jet core that is crossing through the central
plains Friday. A warm front extending east of the low will result in
developing showers and thunderstorms for the Lower Michigan with
precipitable watter values pushing well over an inch. While the GFS
solution would be more progressive to a south-north precipitation
track, the ECM would point to a longer duration heavy rainfall
event. Given recent rain, high river levels and Wednesday`s system,
this will certainly be something to watch.

A third and final wave will depend on which model solution is right
on Friday`s system. The GFS would provide another cold front
convective line for Saturday, while the ECM would suggest lead to
showery remnants behind the back side of the system. This could also
have a great impact on temperatures. Should the ECM verify,
temperatures could be suppressed to the 60s, as opposed to the milder
GFS.


&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 124 AM EDT Sat Apr 22 2017

No changes are warranted to the current forecast.

Dry air continues to work into the Great Lakes Region. Mainly
high clouds are expected tonight with a clearing trend as we head
into Saturday. Northeast winds of 5-10 knots are likely with
mixing from mid-morning through the afternoon. VFR conditions are
expected to remain locked in through the period.


&&

.MARINE...
Issued at 309 AM EDT Sat Apr 22 2017
With high pressure in control of our weather...no marine headlines
are forecasted.

&&

.HYDROLOGY...
Issued at 105 PM EDT Fri Apr 21 2017

Wednesday night to Thursday rain totals ranged from 0.5 to 1.5
inches across a majority of the area. As a result, several river
points are rising again, prolonging the high river levels
experienced for much of the season so far. Crests are not expected
to approach what has already occurred earlier this month.
Fortunately, the next chance of rain will hold off until late
Tuesday.

&&

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

$$

SYNOPSIS...MJS
SHORT TERM...MJS
LONG TERM...JAM
AVIATION...JAM
HYDROLOGY...CAS
MARINE...MJS



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