Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 201600
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1200 PM EDT FRI MAY 20 2016

LATEST UPDATE...
Hydro

.SYNOPSIS...
Issued at 312 AM EDT Fri May 20 2016

Dry conditions will continue through into early next week. High
temperatures will slowly trend upward during this time. A chance of
showers and thunderstorms returns to the area beginning Tuesday and
persists through Thursday.

&&

.SHORT TERM...(Today through Sunday)
Issued at 312 AM EDT Fri May 20 2016

No impact weather is expected. There is a low chance of rain showers
brushing the far southeast forecast area early Saturday morning as
the upper potential vorticity max currently exiting the Southern
Plains and its associated precipitation shield tracks east-northeast.

High temperatures over the next few days could easily end up
over-performing relative to the current forecast. 00Z APX/DTX
soundings showed a deep mixed layer to 700 mb. In patterns like
this it is common to have the residual mixed boundary layer carry
over to subsequent days and get incrementally deepened by
successive days of insolation. Forecast models struggle with this
process and are often playing catch-up with forecast highs. The
greater degree of mixing could also produce slightly lower than
expected relative humidities. This is addressed in the fire
weather section below.

.LONG TERM...(Sunday night through Thursday)
Issued at 312 AM EDT Fri May 20 2016

The long term is beginning to look a bit wetter than the current
pattern as high pressure over the Great Lakes moves east. A cold
front is going to approach the western Great Lakes Monday night. We
included a slight chance of tsra in the grids Monday night, but it`s
certainly possible that it`ll be dry as the ridge to the east is
slow to move out. As south flow increases, so will moisture and
instability. The air will begin to feel humid by Tuesday as
dewpoints take aim at 60. We`ll see the higher dewpoints for much of
next week along with highs in the mid to upper 70s.

Low pressure in the Plains will eject northeast toward Wisconsin
late in the period and thunderstorm chances will increase
accordingly.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 736 AM EDT Fri May 20 2016

High confidence for VFR at all terminals through the entire TAF
period. Increasing cloudiness with bases well above 10000 FT will
be the only feature of note. A lake breeze at the MKG terminal this
afternoon will shift winds to the west.


&&

.MARINE...
Issued at 312 AM EDT Fri May 20 2016

Expect a slight increase in winds beginning Saturday. This pattern
will have to be watched as there is potential for localized small
craft conditions near the shore particularly farther north by the
bluffs. The favorable pattern is for a surface high approaching
Lake Michigan from the northwest. This allows a significant
pressure gradient to develop between thermal ridging/pressure
troughing over Lower Michigan and pressure ridging over Lake Michigan
associated with the air modified by the cold lake water. Otherwise...winds
should stay generally below 15 knots and waves 2 feet or less.


&&

.FIRE WEATHER...
Issued at 312 AM EDT Fri May 20 2016

There is a distinct possibility that maximum temperatures through
the weekend could exceed what is currently forecast and relative
humidity could get around 10 percent lower than forecast. Red flag
conditions are not anticipated however because winds should remain
light.

&&

.HYDROLOGY...
Issued at 1200 PM EDT Fri May 20 2016

The lone advisory that is out at this time is Maple Rapids. River
levels may fall low enough to cancel this by early Saturday morning,
if not by late tonight. There are no concerns at this time.

Dry air continues to dominate the overall weather pattern for now.
A shower or two may develop along the Indiana/Michigan border, but
should stay far enough south to keep our forecast area void of
rainfall. We then get into plenty more sunshine Saturday through
the daytime hours Monday. Chances for rain gradually increase late
Monday through the middle of next week. While conditions look
wetter and more active for that period, variability in the medium
range models make the extent of this moisture questionable. By
that time, rivers will have fallen and may have some room to
manaeuver.

&&

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

$$

SYNOPSIS...TJT
SHORT TERM...TJT
LONG TERM...04
AVIATION...TJT
FIRE WEATHER...TJT
HYDROLOGY...JAM
MARINE...TJT



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