Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 241208

Area Forecast Discussion
National Weather Service Grand Rapids MI
708 AM EST Fri Nov 24 2017


Issued at 312 AM EST Fri Nov 24 2017

A breezy day is in store with sunshine and highs in the 50s,
before a cold front brings clouds and a few light rain showers or
drizzle tonight and Saturday. Dry conditions are expected Sunday
through mid week with above normal temperatures continuing.


Issued at 708 AM EST Fri Nov 24 2017

Have added some sprinkles to the fcst this morning north of a
Whitehall to Mt Pleasant line as echoes are showing up on radar
off of Ludington and moving east. Latest RAP RH progs indicate
that the mid level cloud deck producing these echoes will lift off
to the north later this morning so only carried the sprinkles
through 15Z.


.SHORT TERM...(Today through Sunday)
Issued at 312 AM EST Fri Nov 24 2017

Challenge today is how warm we get. Low level cyclonic flow
ahead of approaching front implies decent mixing today. However
fcst soundings indicate a strong inversion above 1200 ft and late
November sun angle is not much help, so mixing down the very warm
air around 10-12C seen at 925/850mb probably will not happen.
Still, the 2 meter temps and MOS guidance supports highs in the
mid 50s over much of the area today which is about 15 degrees
above normal for this time of year.

Cold front arrives tonight and brings with it a chance of light
rain showers, mainly north of I-96. Cold advection is not
particularly strong behind the front on Saturday, but the moist
cyclonic low level flow off Lake MI will support lingering clouds
and some patchy light drizzle. The shallow moisture and low
inversion heights support little more than that.

While dry conditions are expected Saturday night and Sunday, low
clouds may persist due to continued low level westerly flow off
the lake. Am skeptical of our going sunny Sunday fcst and will
trend less optimistic with partly sunny wording.

.LONG TERM...(Sunday night through Thursday)
Issued at 312 AM EST Fri Nov 24 2017

Not much change in the grand scheme of the long term portion of the
forecast compared to previous thinking. We will start out the period
Sun night dry, which will last at least into Tue. Also during this
period, we will see significant warm air advection that will push
max temps on Tue likely well into the 50s.

The first chance of rain will start as early as Tue as the cold
front will be sliding through the area, although the chc on Tue does
not look very good. The front will be pushing into a warm air mass.
However, the air mass does not look to be all that moist as the flow
ahead of the front is not really directly from the Gulf.

The better chance of rain will likely hold off until Wed night into
Thu. The cold front will likely sink far enough south that it will
not be a factor in our weather after Tue. Another fairly strong
short wave and associated sfc low comes out of the Srn Plains, which
will have more of a Gulf connection and better chc of rain. The
track of this is still a bit uncertain.

The pcpn chcs will linger a bit into Fri before pcpn clears out by
Sat. The low coming out of the Plains looks to be absorbed by the
nrn stream wave coming in, and could develop a better low. This
would bring rain showers initially, and then potentially mix
with/change over to some snow as colder air eventually makes it way


.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 632 AM EST Fri Nov 24 2017

Main issue today is the strong southerly winds which will be
gusting to 25-30 knots at times by late morning. VFR weather can
be expected with cloud bases at or above 10,000 ft. Tonight the
winds will diminish to around 10 knots toward midnight then shift
westerly with the arrival of the sfc cold front. Expect cigs to
lower to MVFR after 06Z behind the front, with a few light rain
showers possible.


Issued at 312 AM EST Fri Nov 24 2017

No change to the gale warning at this time. Guidance still shows
strong southerly low level jet arriving shortly after daybreak
and remaining in place through early evening.


Issued at 252 PM EST Thu Nov 23 2017

Water levels in a few rivers remain at advisory stage as of Thursday
afternoon. Water levels on these and other rivers will continue to
slowly fall through the end of the week. No additional hydrologic
concerns exist through the next 7 days as no significant
precipitation is expected. The next chance for rain will be Friday
evening through Saturday, but amounts are expected to remain below a
tenth of an inch.


LM...Gale Warning until 10 PM EST this evening for LMZ844>849.



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