Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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027
FXUS63 KGRR 220600
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
100 AM EST Wed Feb 22 2017

LATEST UPDATE...
Synopsis/Aviation

.SYNOPSIS...
Issued at 100 AM EST Wed Feb 22 2017

Fog will prevail early this morning but will lift by midday. It
will be unseasonably warm today, with highs well into the 60s.
Some record highs are possible this afternoon if we get enough
sunshine. A cold front will come through the area tonight but will
only serve to dry the air out and cool Thursday highs temperatures
by about 10 degrees but that is still well above normal.

A Storm from Colorado will bring showers and the threat of
thunderstorms to the area Thursday night and Friday. Some of the
storms Friday afternoon could be strong. It will also be windy.
The cold front trailing the storm will bring the chance for a
little snow Saturday but accumulations will be light at best. Yet
another storm heads our way for Tuesday of the following week,
that would be mixed precipitation changing to rain.

&&

.UPDATE...
Issued at 1134 PM EST Tue Feb 21 2017

I expanded our fog advisory to include Van Buren and Ingham
counties. Little question this fog will last till at least
sunrise.

UPDATE Issued at 844 PM EST Tue Feb 21 2017

I issued a dense fog advisory for all of the CWA north of I-94
till mid morning Wednesday. Locations like South Haven and
Muskegon already have the fog and inland locations in the advisory
area area mostly below 3 miles and many locations are less than a
mile. All of the hi-res models are forecasting dense fog north of
I-94 by midnight and show it lasting into the mid morning hours.
Also most of the models suggest the southern edge will lift north
with the "WARM FRONT" overnight. For now I will not get cute with
that in the grids. If the southern edge of the dense fog does
lift north with time overnight we can cancel the advisory for
those counties early. One other issue is winds are a touch high
for dense fog but since we now have 4 locations at or below 1/4
miles it seems better to go ahead than wait for it to get
widespread.

&&

.SHORT TERM...(This evening through Thursday night)
Issued at 325 PM EST Tue Feb 21 2017

Primary concerns center on low cloud and fog potential into early
Wednesday, along with prospects for record warmth Wednesday
afternoon. Models are in pretty good alignment bringing abundant
975mb-925mb RH into the region overnight, and with light surface
winds in place this should set the stage for possibly extensive
stratus to form and also areas of fog as well. The GFS LAMP
guidance and to a lesser extent the NAM MOS are showing the
possibility of many locations being socked in by stratus and fog.
This seems plausible through at least 14z or 15z, when it may
eventually lose out the battle to diurnal mixing as SW winds
increase.

Tough call on whether our record-threatening warmth will
materialize Wednesday given it largely hinges on how fast we
clear out after a grey morning. If skies thin out by 15z or 16z,
we have a shot at getting well into the 60s and possibly near 70
closer to I-94. If the stratus is more stubborn than our chances
will be significantly hindered.

Low risk for a shower Wednesday night into Thursday morning as a
weak cold front slips through the region. The precipitation is
largely shown to be confined to northern Lower Michigan based on
the latest GFS/ECMWF. The GEM is further south and stronger with
this surface boundary and has more precip, but it is an outlier.

.LONG TERM...(Friday through Tuesday)
Issued at 325 PM EST Tue Feb 21 2017

The main issue in the long term deals with the potential impacts
from the storm for the end of the week.

Overall the models have trended a little warmer with this system.
Based on this the risk for freezing rain is lower for the onset of
the precipitation across my northern zones Thursday Night.  Thus I
have removed the mention of freezing rain from the forecast.  The
arrival of a low level jet Thursday Night will draw up abundant Gulf
moisture which will lead to some elevated instability. Will keep the
high POPs going with an area of rain and embedded thunderstorms
arriving from the south.

The region is still on track for possible severe weather on Friday.
There are certainly some ingredients showing up.  A powerful mid
level jet up around 100 knots tracks in from the southwest Friday
afternoon and evening.  At the same time instability is shown in the
models in the afternoon...when the low level jet restrengthens. With
a cold front forecasted to track through later in the day...it looks
possible for a narrow line of convection to form along or ahead of
this front. Based on the forecasted wind fields...any stronger
convection could lead to an increased risk for damaging winds.

The region becomes dry slotted for Friday night...so a lull looks
likely in the precipitation.  Wrap around moisture pivots through
the CWA on Saturday. This is when the colder airmass will be in
place.  So it looks like mainly snow showers on Saturday...but
eastern zones could see a r/s mix.

Another storm system may arrive on Tuesday.  This one has a similar
look to it...but somewhat colder.  The track could vary considerably
in the coming days. With a tap to the Gulf...heavy precipitation may
occur. For now will feature a wintry mix at the onset which then
transitions to rain.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 100 AM EST Wed Feb 22 2017

Dense fog did develop as expected (from the 00z tafs). Also as
expected the dense fog was along and north of I-96. The I-94 taf
sites tried to clear this evening they we see the fog by 09z or
so. We actually have a weak warm front pushing through the area
this morning and that is what is causing the fog. So, once the
warm front gets north of here the fog should mix out quickly. Most
of our taf sites inland of MKG should clear by 16z or so. MKG may
have fog linger into the afternoon but I played that taf more
optimisticly. So that will have to be watched. It will be breezy
in the afternoon to with winds gusting to 25 to 30 knots at times.
Mostly clear skies should prevail Wednesday night into Thursday.



&&

.MARINE...
Issued at 844 PM EST Tue Feb 21 2017

Dense fog has already developed over southern Lake Michigan and
will spread quickly north over the rest of the near shore by
midnight or so. As a result I have issued a Marine Dense Fog
Advisory till 18z and will for now call that good. It should last
into the early afternoon Wednesday so I will keep it till then.


&&

.HYDROLOGY...
Issued at 110 PM EST Tue Feb 21 2017

Rainfall amounts Tuesday morning have been light, in many areas
around a tenth of an inch. Rivers will not be impacted by this.
The Muskegon River is rising as the snowpack in the upper portion
of the basin melts. Rain from showers and thunderstorms is likely
Thursday night into Friday. Rainfall amounts are uncertain, but
they could be enough to cause some rivers to rise toward bankfull.

&&

.CLIMATE...
Issued at 325 PM EST Tue Feb 21 2017

The records for our official sites on Wednesday are as follows:

Wed 2/22

Grand Rapids 67 - 1930

Lansing66 - 1930

Muskegon 55 - 1930

These records still could be broken depending on how quickly skies
clear out on Wednesday. Only a handful of sites in Lower Michigan
have ever reached 70 degrees in February. Grand Rapids, Lansing,
and Muskegon have not yet achieved this.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Dense Fog Advisory until 9 AM EST this morning for MIZ037>040-
     043>046-050>052-056>059-064>067-071.

LM...Dense Fog Advisory until 1 PM EST this afternoon for LMZ844>849.

&&

$$

UPDATE...WDM
SYNOPSIS...WDM
SHORT TERM...Hoving
LONG TERM...MJS
AVIATION...WDM
HYDROLOGY...CAS
CLIMATE...Hoving
MARINE...WDM



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