National Weather Service Raw Text Product

Displaying AFOS PIL: AFDGRR Received: 2017-09-13 03:55 UTC


122 
FXUS63 KGRR 130355
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1155 PM EDT Tue Sep 12 2017

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 250 PM EDT Tue Sep 12 2017

Remnants from Irma will continue to weaken into an upper low that
pushes into the Ohio Valley through midweek. As a result, cloud 
cover will increase with low chances for showers during the day 
Wednesday. Ridging redevelops Thursday to provide dry and mild 
conditions that will last through much of the weekend. Precipitation
may return late in the weekend and into early next week.

&&

.SHORT TERM...(This evening through Thursday night)
Issued at 250 PM EDT Tue Sep 12 2017

Remnants of Irma will be the main player for the short term.
Scattered light showers may affect Lower Michigan on Wednesday. 
Otherwise, much of the time is likely to remain dry with near 
normal temperatures.

Visible satellite imagery shows high clouds slowly progressing south 
to north through southern sections of Lower Michigan. Cirrus thins 
out/dissipates rapidly as you travel north of I-94. Expect clouds
to gradually thicken overnight tonight and into Wednesday, mainly
over the southern third of the state. This may hold temperatures 
down into the low and mid-70s along and south of I-96, while
locations to the north make it into the mid and upper 70s. 

The main question will be in regards to precipitation as we go 
from Wednesday morning through Wednesday afternoon. It is in this
timeframe that a thin ribbon of mid-level moisture and lift 
progresses south to north through the area. Northward progress 
eventually stalls around the middle of Lake Michigan and stretches
east-northeast to the Saginaw Bay. High res models continue to 
depict a narrow band of mainly light shower activity along this 
boundary with isolated to scattered activity further south. 
MUCape/LIs look unimpressive non-existent in much of the CWA. So,
any bets for thunder will likely go unpaid. Precip totals should
remain well under one-tenth of an inch.

Dry air will have some affect of the system as it churns northeast
Wednesday afternoon. Water vapor imagery shows plenty of dry air 
over the Gulf, wrapping up from the south end of Irma and 
eventually northward to the east of the system. As the upper low 
closes in on Ohio, guidance suggests some of this dry air gets 
entrained into the northern fringes. Any shower activity should 
become limited as we head into Wednesday evening.

Upper ridging builds in with a strengthening surface high just off 
to the east. This will result in dry conditions with mild southerly 
flow through the day Thursday.

.LONG TERM...(Friday through Tuesday)
Issued at 250 PM EDT Tue Sep 12 2017

Only forecast issue in the extended is timing some showers through 
Lower Michigan early next week as upper ridging is flattened by a 
northern stream trough. There is fairly good consistency with the 
timing of the trough although the amplitude varies quite a 
bit between model runs. 

No changes to the blend were made. Max temperatures Sunday could 
reach the lower 80s, but maxes were left alone for now since clouds 
could arrive by the afternoon and keep maxes more in line with 
guidance.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1130 PM EDT Tue Sep 12 2017

VFR conditions will continue at all the terminals overnight.
Conditions will gradually deteriorate to MVFR at our southern
terminals during the mid mornings hours Wednesday as low clouds
and scattered showers move in from the south. 

The showers will gradually develop further north and affect our 
northern terminals by late Wednesday morning/early Wednesday 
afternoon. Showers will exit the area Wednesday evening and 
conditions should return to VFR at all the terminals Wednesday 
evening as well. Wind speeds will remain blo 10 kts at all the
terminals through the next 24 hrs. 

&&

.MARINE...
Issued at 250 PM EDT Tue Sep 12 2017

Aside from a few showers Wednesday, impacts are null on Lake
Michigan over the next few days. Winds are expected to be light
limited wave activity expected.


&&

.HYDROLOGY...
Issued at 1135 AM EDT Tue Sep 12 2017

Rivers are running at or below normal levels and dry weather will 
dominate for much of the next week under persistent high pressure. 
The only exception may be Wednesday, as the remnants of Irma produce 
areas of light rain. Amounts will likely be under a tenth of an 
inch, and many areas may not see any rain. Abnormally dry conditions 
across Southern Lower Michigan (as defined by the National Drought 
Mitigation Center) will continue with little relief and rivers will 
continue to run a little low.

&&

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

$$

SYNOPSIS...JAM
SHORT TERM...JAM
LONG TERM...Ostuno
AVIATION...Laurens
HYDROLOGY...63
MARINE...JAM