Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

FXUS63 KGRR 252024

Area Forecast Discussion
National Weather Service Grand Rapids MI
324 PM EST Sat Feb 25 2017

Synopsis/Short Term/Long Term/Hydro/Marine

Issued at 324 PM EST Sat Feb 25 2017

Lake effect snow showers will gradually diminish tonight, with any 
additional accumulation remaining under an inch.  Another weak 
system will produce light snow Sunday morning, mainly north of I-96. 
Some rain could mix in by afternoon.  Again any accumulation on 
Sunday will remain under an inch.  Then a dry period is expected 
late Sunday night through Monday evening.  However rain is expected 
to arrive from the south late Monday night.

A soaking rain should continue Tuesday and Wednesday, before the 
precipitation changes to snow Wednesday night.  The latter portion 
of next week appears to be quieter but cooler.  

Temperatures will be warmer Sunday and this warmer air lingers 
through Wednesday with daytime temperatures mainly 45 to 50.  Then 
we should cool down late in the week.  Highs Thursday through 
Saturday should mainly be 30 to 35.


.SHORT TERM...(This evening through Monday night)
Issued at 324 PM EST Sat Feb 25 2017

THe lake enhanced snow will gradually wind down this evening with 
most additional accums under an inch.  A weak short wave moves 
through Sunday producing light snow I-96 northward.  Then a southern 
stream system moves in late Monday night.

Inversion levels still high enough for the snow showers to continue 
into this evening.  However they quickly drop off as the evening 
progresses.  Feel the 8 PM end time to the advisory still looks 
good.  Additional accums will remain under an inch.  West winds will 
remain brisk until midnight, so some drifting will be possible on 
north/south roads until then.

A short wave crosses the Great Lakes Sunday afternoon.  Some lake 
enhancement might still be in place Sunday morning with a southwest 
flow.  So we will have watch, as this weak system could over-
perform.  So as of now will carry chance POPs with any accums 
expected to be less than an inch.  Most of the available moisture is 
north of I-96, so little pcpn expected south.  Some light rain could 
mix in by afternoon as temps approach 40.  Some light snow may 
linger into Sunday evening across Highway 10, otherwise we will move 
into a dry period.

Zonal flow and surface ridging will bring this dry weather for late 
Sunday night through Monday evening.  Solid warm advection Monday 
will push temps well into the 40s under partly to mostly sunny skies.

Low pressure will move to about the Kansas City area by daybreak 
Tuesday.  A warm front sharpens up overnight Monday near the MI/IN 
border.  Isentropic lift across this front will bring rain, 
especially for areas south of I-96.  Pcpn type appears all rain with 
overnight lows in the mid and upper 30s.

.LONG TERM...(Tuesday through Saturday)
Issued at 324 PM EST Sat Feb 25 2017

This will be an up and down sort of weather pattern this coming 
week. We get a warm up early in the period only to see a sharp cool 
down mid to late week. There could be yet another warm up with an 
even bigger cool down beyond that.

I key to this forecast is the forecast development by of a large 
blocking upper high near Greenland in the Wed to Thursday time 
frame. It has been my experience that this means cold to very cold 
weather here.  As it will force a deep trough over Central Canada 
into the Great Lakes. There is some suggestion by early in the 
following week we could see an upper low near the Great Lakes, if 
that happens it will be much colder than we have seen over over a 
month here. There would be warm up between the system Thu into Fri 
and that system in the Sun to Monday time frame. 

As for the system in the Tue to Wed time frame, this in another one 
of those coupled jet systems (like the one yesterday).  We have a 
system over the Bering sea (as I write this) that tops the upper 
ridge over central Alaska tomorrow and then digs a deep trough over 
western North America as far south and California.  That of course 
pops up an upper ridge over eastern CONUS (something we have seen 
happen frequently this winter),  As the system comes into the 
central CONUS we get a coupled jet from the departing northern 
stream system and southern stream jet. That results in strong 
moisture transport north into Michigan thanks to a 40 to 50 knot low 
level jet into southern Michigan Tuesday night.  So, once again it 
will rain and this could mean around a half inch of QPF.  It would 
not be out of the question to get thunderstorm Wed during the day 
ahead of the cold front but I did not put that in yet.  

Of course the cold air comes back behind the system so the rain 
changes to snow Wed night than we get lake enhanced snow into 
Saturday morning. As shortwaves move through the flow they will 
enhance the life and there will be good lift in the DGZ Thu night 
into Friday.  A warm advection snow event is possible Saturday.

The bottom line it will be stormy week with precipitation likely 
nearly every day Tue through Friday.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1250 PM EST Sat Feb 25 2017

Expect IFR snow showers to continue till around 00z at MKG, GRR
and AZO while BTL, will have occasional MVFR snow showers. LAN and
JXN will have MVFR ceilings with flurries and the ocnl MVFR VIS 
snow shower. 

Tonight the moisture thins out so the snow showers should come to
an end by 03z or so. I would think VFR cigs will prevail.  

Sunday should mostly be VFR but we will have to watch for the
chance of a southwest flow snow shower event mid morning into mid
afternoon. That event would only impact MKG.


Issued at 324 PM EST Sat Feb 25 2017

Took the gale warning down earlier this afternoon and now have a 
small craft advisory in affect.  West or southwest winds remain 
brisk into Sunday evening keeping the lake rough.  Subsiding waves 
should finally occur late Sunday night.


Issued at 324 PM EST Sat Feb 25 2017

The Muskegon River basin was impacted the greatest with widespread 
rainfall of 1"-2". As a result, crests from Evart to Croton will be 
very close to bankfull. Significant flooding is not a concern but 
areas immediately adjacent to the river banks may experience 
overflow. The Chippewa River should crest just above bankfull as 
well from the heavy rains yesterday. The Maple River and Grand River 
will also experience some rises, though nothing significant and any 
above bankfull stages will have limited impacts immediately adjacent 
to the rivers.

Looking ahead, rain returns to the forecast Tuesday into Wednesday 
before changing to snow. This rain may act to slow the falls on the 
rivers for the middle of next week but additional rises are not out 
of the question.


MI...Winter Weather Advisory until 8 PM EST this evening for MIZ037-

LM...Small Craft Advisory until 5 AM EST Monday for LMZ844>849.




National Weather Service Glossary of Abbreviations