National Weather Service Raw Text Product

Displaying AFOS PIL: AFDGRR Received: 2019-03-15 17:39 UTC


222 
FXUS63 KGRR 151739
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
139 PM EDT Fri Mar 15 2019

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 330 AM EDT Fri Mar 15 2019

- Rain showers becoming mixed with snow today, changing to all
  snow by tonight
 
- Light snow accumulations of an inch or so possible, mainly near
  and west of Highway 131

- Slick roads possible late tonight and early Saturday morning as
  temperatures dip below freezing 

- Lengthy period of benign weather with seasonal temperatures 
  next week

&&

.UPDATE...
Issued at 1053 AM EDT Fri Mar 15 2019

No major updates with the forecast this morning, other than
bumping the pcpn chances up to account for the latest radar
trends. 

Drizzle from earlier this morning, is transitioning to more solid
rain showers as the DGZ becomes saturated this morning. The DGZ is
both becoming saturated with deeper moisture coming in ahead of 
the next short wave, and due to temperatures aloft dropping in the
saturated layer. 

We are now also starting to see pcpn changing over to some snow 
across the west with the temperatures aloft dropping. We will see
more snow mix in this afternoon. We do not expect to see much
accumulation this afternoon outside of a heavier burst with temps
above freezing, and ground temps above freezing also. The best
chance for some light accumulations will come this evening once
we lose daylight, and before the short wave passes by. 

Some slick spots will become possible overnight as temps drop
below freezing later. We do not expect this to cause significant
impacts, especially with tomorrow morning being a weekend. 

&&

.DISCUSSION...(Today through next Thursday)
Issued at 330 AM EDT Fri Mar 15 2019

Strong low level cold advection and cyclonic flow on the back side
of the departing sfc low, paired with sharp mid level troughing 
and deep moisture, will lead to widespread showers today. 
Precipitation type is somewhat complicated however since sfc 
temperatures holding in the upper 30s supports mostly rain 
whereas H8 temps falling to around -7C this afternoon suggest a 
changeover to snow or a least a mixture developing. 

Typically in this type of late season lake effect/lake enhanced 
set-up, the higher elevations north of Big Rapids are favored for
more in the way of snow. However snow could also be more favored 
at any location today during times of heavier precipitation rates.
A vorticity maxima which tracks across far srn Lwr MI may very 
well support some more intense showers, particularly near and 
south of I-96. Either way, getting snow to stick on the roads and 
cause travel impacts today will be challenging given the recent 
warmth and rain. However a coating to one inch on the grass is
certainly possible this afternoon. 

Tonight we should see a transition to more of a pure lake effect 
scenario, with cooler temperatures and nighttime promoting a 
changeover to all snow. Some light accumulations, generally under
one inch, are possible near and west of Hwy 131. Some slick spots
may develop overnight into Saturday morning, before sfc temps
climb above freezing again Saturday afternoon.

Chilly pattern persists all weekend as upper trough remains over 
the Great Lakes Rgn. A clipper low passing just south of the 
state late Saturday night and Sunday morning could produce a 
dusting of snow along and south of the I-94 corridor. 

Surface ridging and cool air mass looks to dominate through the
middle part of next week, although a weak cold frontal passage on
Tuesday night/Wednesday could produce some light precipitation. 
Temps appear to moderate toward the end of next week - with no 
impact weather expected at this time. 

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 139 PM EDT Fri Mar 15 2019

Light rain is in the process of changing over to light snow from
west to east this afternoon. We are seeing IFR cigs for the
western terminals, while MVFR cigs are present across the east.
Some spotty IFR vsbys are also present with drizzle and also where
pcpn has changed over to snow up north. We expect a general
improvement with cigs and vsbys over the next few hours,
before vsbys drop again for a few hours later this afternoon and 
this evening as snow showers intensify as the wave moves through.

Once the wave moves through, we expect a lasting improving trend
to VFR overnight and through Sat. Some light snow showers will be
possible, but should produce little to no impacts. Some locations
inland may even clear out tonight, like at KLAN and KJXN. Wind
gusts will come down overnight.  

&&

.HYDROLOGY...
Issued at 330 AM EDT Fri Mar 15 2019

The combination of 36-hour rainfall totals from one half inch to 
nearly two inches with the rapid melting of the snowpack over frozen 
ground has led to considerable run off and flooding mainly along and 
north of I-96 where emergency management officials report road 
closures due to high water. Area rivers have also experienced 
significant rises over the past 12 hours, with the Chippewa River at 
Mt. Pleasant, Maple River at Maple Rapids, Pine River at Alma 
already in minor flood stage. The Rogue River at Rockford and Grand 
River at Comstock Park and Robinson Township are expected to reach 
minor flood stage by this evening, with the Muskegon River at 
Bridgeton and Newaygo expected to reach minor flood stage Saturday. 
With these considerations in mind, an areal flood warning remains in 
effect for areas mainly north of I-96, river flood warnings where 
minor flooding is already occuring or likely to start within the 
next 24 hours, and a river flood watch remaining for the Muskegon 
River at Bridgeton and Newaygo. 

Most area rivers are expected to crest this weekend with a gradual 
decrease in water levels into early next week. Moderate flood stage 
is not expected to be met at any forecast point after the 
recent snowmelt/rainfall event. 

While low temperatures through this weekend and into early next week 
will at times fall into the upper teens to lower twenties, no 
significant ice build-up is currently forecasted.  However, the 
recent mild temperatures and rainfall likely broke up the majority 
of ice in area rivers leading to a low but nonetheless still present 
threat for ice jams, especially on the White and Muskegon Chippewa 
basins. People with interests along rivers in Central Michigan 
should continue to be alert for rapid changes in river levels.

&&

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

$$

UPDATE...NJJ
SYNOPSIS...Meade
DISCUSSION...Meade
AVIATION...NJJ
HYDROLOGY...Borchardt