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Area forecast discussion 
National Weather Service Gaylord Michigan
127 am EST Sat Dec 20 2014

Near term...(today through tonight)
issued at 124 am EST Sat Dec 20 2014

..stratus west and sun east...

Synoptic pattern and observations:

Early this morning...not much change over the last 18 hours in a very
slow moving. A very wavy upper air pattern remains across the
Continental U.S....with a couple of over the East Coast and
another in the Lee of The Rockies. Several weak troughs were
surrounding these ridges...including one working into the upper
Mississippi Valley. This wave was producing some light snow across
northern Minnesota. Over northern Michigan...surface high pressure was centered with calm
winds and still just dealing with low cloud/stratus.

At this time...widespread stratus over Lake Michigan (and still across most
of the central Continental U.S./Mississippi valley) continues to work north up
the lake...and impacting portions of the northwest lower coastline.
Elsewhere...skies were clear with very chilly temperatures in the
single digits below zero to 10-15f. In the warm as the
upper 20s.

Forecast challenge: evolution of the stratus.

Synoptic pattern evolution and associated weather:

Surface high pressure slower to shift east...until tonight...when there
is a bit more confidence in the development of a weak south-southwest flow. This
developing south-southwest ought to bring the stratus further inland through northwest
lower and eastern upper through the day. Minimal mixing with light
winds likely to not mix anything of significance out. The idea was
for this slightly west component to the cloud layer bring
that stratus into NE lower tonight. This is still the forecast...but
there are hints that as upper troughing sharpens in the Central
Plains with incoming initial Pacific energy...the cloud layer flow
could back more out of true south. This does provide a threat for
the stratus to move due north...and leave NE lower in more of a
mostly clear scenario. Will have to see how this plays out.

High temperatures today in the upper 20s to lower 30s. Lows tonight with a
huge range again...near zero in low lying spots in NE lower...and
middle 20s under clouds.


Short term...(sunday through Sunday night)
issued at 124 am EST Sat Dec 20 2014

High impact weather potential: a quick burst of snow increasingly
likely for northern areas Sunday night...with expected wet/greasy
nature perhaps making for some slick travel.

Sort of the "easy" portion of the forecast as we head through the
weekend and begin the work least when compared to the
headaches that await thereafter (more on that fun stuff below). The
overall flow regime through this period will remain Pacific-
dominated aloft...with a couple of shortwaves in play though none of
them particularly interesting for our region (at least not yet). At
the surface...elongated low level ridging stretched from Quebec
through the southern states on Sunday will steadily March eastward
in the still-progressive pattern...setting up strengthening low/middle
level return flow into the Great Lakes by Sunday night/Monday ahead
of crashing heights through the plains states as quite the punch of
Pacific jet energy (to the tune of 175+ knots!) Rolls through the
Pacific northwest states. Couple that return flow with the fact that
widespread stratus already exists from Texas all the way up through
the Canadian prairies and into the western lakes...and the basic
conclusion is that at some point northern Michigan will pay for the
recent sunny weather.

That payment should come on Sunday as we sneak increasing moisture
beneath a continued sharp low level inversion...with lower stratus
likely filling in for many spots into the afternoon. All the
while...overall cloud cover will be enhanced by increasing middle level
warm advection ascent ahead of a weakish lead shortwave lifting from
the Central Plains. 00z guidance suit has latched onto the notion of
a stronger lead northern stream trough into Sunday night (verified
per water vapor analysis of enhanced energy rolling through Montana
currently)...such that our Sunday night burst of warm advection
appears stronger and a touch farther east than initially thought. As
such...and in line with what usually happens in these setups...can
foresee a quick burst of snow developing somewhere across northern
lower (probably north of M-72) through late evening and being
maximized toward The Straits/eastern u.P. Roughly 03z-08z. Nothing
too major with warm thermal profiles (low snow-liquid ratios) but a
quick inch (maybe 2?) Of some greasy wet snow may slicken up travel
for a time as surface temperatures hang just below freezing.


Long term...(monday through friday)
issued at 124 am EST Sat Dec 20 2014

High impact weather potential: all sorts of potential hazards
depending on the eventual evolution of our midweek system. Localized
heavier rains...heavier snow...and very strong winds are all
possible during the Tuesday-Christmas day period. A cautionary tale:
despite some media hype of one solution appears favored
over the other just yet...and all scenarios are on The Table as far
as this storm system GOES...including at least the small potential
for a major snowstorm for parts of northern Michigan.

All eyes are of course on the evolution of our Christmas week storm
system...with still quite a bit of uncertainty regarding the
ultimated evolution of said system. This uncertainty can be tied
directly to the climatologically rare strong Pacific jet and
shortwave train roaring into the lower 48 during this time...with
even forecast analogs having a difficult time in picking out any
similar setups over the past 35 years (see cips guidance with very
low correlation scores...some even negative!) All of this is to say
that things remain changeable over the coming days and one should
count on changes in current forecast expectations.

The overall pattern setup is as such: lead stronger shortwave south
of the Aleutians currently will get plowed ashore Sunday night/
Monday as 180 knot Pacific jet rolls inland...leading to rapid
trough amplification through the plains and middle miss valley.
Additional shortwave energy in the Pacific wave train will get
punted into that developing trough come Tuesday...helping further
amplify the middle-Continental U.S. Trough and eventually leading to this feature
taking on a strongly negative tilt. Of course...the atmosphere has
to respond to such a drastic and rapid change and it will do so by
first inciting cyclogenesis over the northern plains Monday beneath
a core of enhanced upper divergence. That system will fill as it
drifts toward the western lakes and all further upper support shifts
somewhere toward the Tennessee Valley or Middle Atlantic
line with tremendous upper jet divergence developing over that
region. In fact...very interesting to note similarities between the
January 1978 jet setup and this one as modeled by the European model (ecmwf) with
continuity the past 24 hours. The difference this go around is a
severe lack of upstream cold air being sucked into this system...
such that the surface low track will have huge ramifications as to
exactly what spots see various types of precipitation. Give the lack
of any blocking high...don't foresee any freezing rain/sleet threat
with this setup...but more of a rain or snow scenario...with at
least the potential that some spots (even in our cwa) could see
appreciable snowfall by the time Christmas day arrives.

A look at the details...which again are likely to change over the
coming days.

Monday-tuesday: precipitation threat ends quickly Monday morning as middle
levels and maybe even the low levels dry out briefly. However...
northern stream occluding low level cyclone looks to lift its
occluded front toward the region into Monday evening/night...with a
brief surge of both warm advection ascent further aloft and enhanced
middle level difluence most likely driving a band of precipitation through the
area. Looking like a mostly rain scenario for northern lower no
matter your model of choice...with even the consistent European model (ecmwf) pegging
a warmer boundary layer sufficient to melt snowflakes over much of
northern lower. Eastern upper may be more of a snow to rain
transition into Tuesday as the middle level trowal feature elongates
nearby while the really dynamic show gets underway through the
Southern Plains and southeast states into Tuesday evening.

Tuesday night-wednesday: the period of most uncertainty as we await
to see the evolution of the kicker shortwave diving through the
Southern Plains. That little feature will be of key interest as it
will determine the speed at which our middle level cyclone closes
off...thus modulating the north and westward extent of the surface
cyclone. Hard to ignore the continuity of the European model (ecmwf) and to some
extent the ggem...though a peek at their various ensembles still
looks like a Dart board peppered with numerous possible surface low
locations. All told...gut feeling in this whole situation is that
much of northern Michigan will experience mainly rain through even a Lake Huron track will wrap back significant
warm air down low. Will continue to trend the forecast in that
direction...with surface temperatures perhaps even surging well into the
40s (maybe even a 50 far southeast?) Should a more western track

Christmas evening (wednesday night)-Christmas day and into friday: rapid
deepening of the surface low somewhere nearby (doesn't really matter
exactly where by this point) should wrap cold air back into the
region quickly...changing precipitation back over to snow. All the while...
a very tight gradient and quick burst of cold advection has the
potential to bring some very strong winds...with some downright
nasty travel certainly possible Christmas morning. That should wind
down through the day but with wind conditions persisting into the
evening. Could be a Little Lake effect into Friday though the extent
of cold air in the wake of our system remains in question. Honestly
not that worried that far out (plenty to deal with already)...though
the overall trend does appear to be for colder conditions to make a
return as we head toward the tail end of the month.


Aviation...(for the 06z tafs through 06z Saturday night)
issued at 1243 am EST Sat Dec 20 2014

..MVFR stratus working up the northwest lower coast...

Very difficult ceiling forecast...always is with stratus. Overall
trend will be for surface high pressure to move east and we get into a
more confident weak south-southwest flow...allowing widespread stratus over
Lake Michigan to spread up the northwest lower coast line...impacting all
3 airports. Meanwhile...there is just a small chance for stratus
scraping apn off Lake Huron...but have opted to leave it out of
the forecast...for the entire taf period.

Trend will be for more and more confidence over the next 24-36
hours...of stratus gradually spreading east...eventually into apn
as well.

Light winds the entire period.


Apx watches/warnings/advisories...


Near term...smd
short term...Lawrence
long term...Lawrence

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