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Area forecast discussion 
National Weather Service Grand Rapids Michigan
248 am EST Sat Jan 31 2015

Latest update...
synopsis/short term/long term/Hydro

issued at 248 am EST Sat Jan 31 2015

Low pressure moving out of the plains toward the Ohio Valley later
today will bring a swath of snow through Southern Lower Michigan.
Snowfall totals from late tonight through Sunday night could be 8 to
10 inches south of I-94 with lesser totals the farther north you go.
Gusty northeast winds will create blowing and drifting too.
Finally...cold wind chills Sunday night may approach 10-15 below
zero especially if skies can clear inland.

Monday will be a very cold day with highs around 15. Another shot of
Arctic air will moved through Wednesday and Thursday and highs will
retreat to the teens.


Short term...(today through monday)
issued at 248 am EST Sat Jan 31 2015

Forecast concerns deal with the evolution of a winter storm that
will move over the Ohio Valley late tonight through Sunday night. A
long duration snow event is expected from this system.

There wasn/T any major track movement of the low with the 00z model
runs. The European model (ecmwf)/GFS/NAM/Gem take the low from Kansas east across the
Ohio River valley. The 800 mb low takes a track across North Central
Indiana to Toledo. This system has some things going for it and also
against it. At the same time the low is moving east...a cold front
is sinking south. This cold front will move through the County Warning Area late
this afternoon and evening resulting in a cold dry feed of Arctic
air into the County Warning Area. This dry air will be a mitigating factor to some
degree with the developing precipitation shield as it tries to move

As the low moves out of the plains a 60 knots low level jet develops on the east
side and will draw up some Gulf moisture. Isentropic analysis on the
290k surface shows the highest mixing ratios over central/northern
Indiana closer to the track of the 800 mb low. This should result in the
heaviest snow remaining south of the County Warning Area and also mean the far
southern row of counties along and south of I-94 will see the most

Overall...we weren't overwhelmed by the Omega in this system. And
the dgz is high...around 12k feet. Given the cold air in place after
the front moves through...the type of snow that falls will be very
light...around a 18:1 ratio. Temperatures -15 to -20c in the dgz
should result in plate formation rather than higher accumulating
dendrites. This may result in lower visibilities and a bit less
accumulation. Winds will gust to 25 to 35 miles per hour as the low deepens
over Indiana. This will lead to blowing and drifting conditions
Sunday especially over the southern counties.

Quantitative precipitation forecast and snow ratio combinations yield 8 to 10 inches over the southern
row of counties from 00z tonight through Sunday night. Totals from
Holland to Grand Rapids and Lansing look like they will be in the 5
to 8 inch range...with highest totals in the southern portion of
those counties.

This will be a decent snowstorm but probably won't be crippling. As
such we opted for a Winter Weather Advisory versus a warning for all
the northern row of counties and stratified it into 3 segments based
on snowfall totals.

Low temperatures Sunday night will range from 5 below to 5 above. Gusty
winds resulting from the departing low will create wind chills 10 to
15 below zero.

Long term...(monday night through friday)
issued at 248 am EST Sat Jan 31 2015

Still looking at a compact and fast moving upper pv anomaly to bring
a round of lake enhanced snow Tuesday through Tuesday night.
Currently have Monday night dry...but there could be light snow
falling by the Tuesday morning commute. For the entire Monday night
through Tuesday night timeframe...snow totals should be modest at
1-3 inches with 4 inches near the Lakeshore.

Cold front in the wake of the pv anomaly should be through the area
by Wednesday morning. This will be followed by below normal
temperatures the rest of the work week with highs Thursday/Friday in
the teens. Cold temperatures/poor microphysics combined with
shallow/limited moisture will result in little if any lake effect
snow accumulations during this time.


Aviation...(for the 06z tafs through 06z Saturday night)
issued at 1158 PM EST Friday Jan 30 2015

Areas of MVFR clouds from earlier have dissipated for the most
part with the exception of the Lake Michigan shoreline including mkg.
These clouds will probably persist much of tonight and Saturday
at mkg given that the low level flow is out of the southwest off
Lake Michigan... and may also impact GRR.

Otherwise VFR conditions are expected south and east of GRR
tonight and Saturday morning with scattered-broken cloud bases mainly
above 8000 feet. Some lower ceilings of 2500-4000 feet should spread from
northwest to southeast Saturday afternoon as a cold front

Flight conditions at all the terminals will continue to trend
downward after 00z Sunday as the frontal boundary slips slowly
south through the area... with MVFR becoming more widespread with
time. The outlook beyond 06z Sunday is for widespread IFR to
develop as snow overspreads the area.


issued at 248 am EST Sat Jan 31 2015

Ice formation is the main concern during the next few days. Highs
around 20 Sunday and around 15 Monday will be favorable for ice


GRR watches/warnings/advisories...
Michigan...Winter Weather Advisory from 7 PM this evening to 6 am EST
Monday for miz043>046-050>052-056>059-064>067-071>074.



short term...93
long term...tjt

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