National Weather Service Raw Text Product

Displaying AFOS PIL: AFDGRR Received: 2020-09-15 17:25 UTC

FXUS63 KGRR 151725

Area Forecast Discussion
National Weather Service Grand Rapids MI
125 PM EDT Tue Sep 15 2020


Issued at 330 AM EDT Tue Sep 15 2020

-Warmer with smoky skies today and Wednesday

-Chilly Thursday through Sunday, patchy frost

-Dry pattern prevailing 


.DISCUSSION...(Today through next Monday)
Issued at 330 AM EDT Tue Sep 15 2020

--Warmer with smoky skies today and Wednesday-- 

Southerly/return flow on back side of departing sfc high sends 
warmer temps into the region today and Wednesday before cold 
front arrives from the north late Wednesday. H8 temps push 18C 
although mixing won't be that deep (more like 900 mb) so we're 
looking at highs mainly in the 70s. Plus the persistent thick 
smoke aloft may help shave a few degrees off the highs.

As far as the smoke aloft is concerned, experimental RAP/HRRR 
smoke guidance keeps it around through Wednesday, but the tail 
end of the 48 hour guidance suggests it may finally be pushed 
south and out of the area on Thursday. This happens as the upper 
trough digs farther south into the region and trajectories turn a 
bit more northerly. 

Interesting too in the experimental guidance is that the smoke 
layer appears to lower as the cold front drops south late 
Wednesday, even suggesting some potential for some low 
concentrations of near surface smoke for a time on Wednesday 

--Chilly Thursday through Sunday, patchy frost--

Cold frontal passage looks a bit quicker in latest guidance and  
slips south through the region late Wednesday afternoon and 
Wednesday evening. Precip potential still looks low although can't
rule out a few light rain showers with the band of low clouds 
accompanying the front. 

Surface ridging is also quicker to build in behind the front, 
now implying a frost potential developing as early as Thursday 
night north of I-96. The surface ridge and associated cold/dry air
mass hangs around through early Sunday, so the nighttime frost
threat will exist on Friday and Saturday nights too. Best threat 
for widespread frost is north of I-96 on Friday night. 

--Dry pattern prevailing--

With dry air mass and surface ridging generally prevailing, the
next 7 days will remain mostly dry other than the potential trace
amounts with the Wednesday evening cold frontal passage. 
According to ECMWF ensemble data, our next decent chance of 
measurable rain is not until a week from Thursday. 


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 121 PM EDT Tue Sep 15 2020

The low level moisture remains limited so any cloud cover will
likely remain VFR. Gusty winds are possible today and again on
Wednesday as a front nears from the north. Values could approach
25 knots. This front is not expected to push through until after 
18z Wed.


Issued at 330 AM EDT Tue Sep 15 2020

No changes needed to the existing marine headlines. Latest wave 
guidance continues to support hazardous conditions developing 
north of holland due to increasing southerly flow today and 
persisting into Wednesday. Winds shift northerly behind the front 
on Wednesday night and the northerly flow continues Thursday and 


MI...Beach Hazards Statement through Wednesday afternoon for MIZ037-

LM...Small Craft Advisory until 5 PM EDT Wednesday for LMZ846>849.