Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 191925
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
325 PM EDT Sun Mar 19 2017

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

.SYNOPSIS...
Issued at 325 PM EDT Sun Mar 19 2017

A cold front will move across the state Monday triggering some light
rain and perhaps a thunderstorms south of I-95. Dry and colder
weather is expected Wednesday with highs only in the mid 30s. Then a
warm up into the 50s will occur by the end of the week.

&&

.SHORT TERM...(This evening through Tuesday night)
Issued at 325 PM EDT Sun Mar 19 2017

Forecast concerns deal with pcpn chances later tonight and Monday.

A cold front currently over the Mississippi Valley will move east
through the cwa Monday. Ahead of it, instability has developed over
Missouri and some of this instability will move toward far southern
Lower Michigan tonight. We`ll see showers develop ahead of the
approaching front and a few elevated storms are possible tonight
south of I-94. Upper level support is lacking with this system; it
remains in Canada. Thus pcpn amounts will be limited. However, as a
wave develops along the front over Illinois tonight, moderate to
high pops seem warranted Monday. After the front passes, high
pressure quickly builds in and Monday night through Tuesday night
will be dry.

.LONG TERM...(Wednesday through Sunday)
Issued at 325 PM EDT Sun Mar 19 2017

The main challenge with the long term deals with the precipitation
type for Thursday night. The latest incoming data suggests this will
be mainly a rain event. The initially low wet bulb temperatures from
the High Res Euro...could support a brief period of snow...but the
warm air advection is strong and is shown to quickly warm up the
soundings...even for Harrison.  The GFS is too warm for snow there
through the night with 800 mb dewpoints of 3.7 deg C at 06z for
Harrison. We will need to monitor the surface
temperatures...especially the interior northeast zones. The pattern
does suggest a small risk for zr if we end up with surface
temperatures a few degrees cooler.

It looks like a rather cool day for Wednesday.  The 925 mb thermal
trough will be in place to start the day with values around -12 to
-13 deg C.  Despite the abundant sunshine the weak flow with high
pressure overhead will support only slow modification of the
airmass.  Some locations look likely to stay below freezing.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 110 PM EDT Sun Mar 19 2017

The MVFR cloud deck has been thinning out from east to west across
the forecast area late this morning and early this afternoon. This
trend is expected to continue as we go through the remainder of
the afternoon. KAZO...KBTL and KJXN will likely be the last sites
to see the low clouds scatter out.  Relatively light winds are
forecasted with a weak pressure gradient in place this afternoon.

Tonight rain showers will be moving in from the west late. They
are forecasted to weaken as they move in...and may not make it
to KLAN and KJXN until after 12z. Elevated instability is shown by
some models for Monday morning ahead of the cold front that will
be tracking through. Right now the best potential for a
thunderstorm will be over the southern TAF sites of KAZO...KBTL
and KJXN. There I will have a period of VCTS.

The low level moisture really does not increase until closer to
daybreak on Monday. Thus the TAF forecast will feature ceilings
lowering as we go through the morning...with a risk for IFR for
KMKG by the end of the TAF period.


&&

.MARINE...
Issued at 325 PM EDT Sun Mar 19 2017

Southwest winds 10 to 20 knots will create 2-4 foot waves during the
next 24 hrs. A thunderstorm is also possible

&&

.HYDROLOGY...
ISSUED AT 1047 AM EDT SAT MAR 18 2017

RIVER LEVELS ARE RUNNING AROUND NORMAL TO A LITTLE BELOW NORMAL.
WITH LESS THAN A HALF INCH OF PRECIPITATION EXPECTED THROUGH THIS
WEEKEND AND THEN NO ADDITIONAL PRECIPITATION UNTIL FRIDAY, NO
FLOODING IS EXPECTED ACROSS THE AREA INTO NEXT WEEKEND. THE
PRECIPITATION NEXT WEEKEND MAY BE ENOUGH TO PUSH RIVER LEVELS UP,
BUT THEY SHOULD REMAIN BELOW BANK FULL.

&&

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

$$

SYNOPSIS...04
SHORT TERM...04
LONG TERM...MJS
AVIATION...MJS
HYDROLOGY...63
MARINE...04



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