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Area forecast discussion 
National Weather Service Gaylord Michigan
732 PM EDT Sat Apr 18 2015

Near term...(this evening through tonight)
issued at 327 PM EDT Sat Apr 18 2015

..some high clouds tonight...

High impact weather potential: minimal.

Pattern synopsis/forecast: early afternoon surface analysis shows
high pressure centered over northwest Ontario building southeast
across the Great Lakes region (3-4mb/3h pressure rises across
northeast Ontario/lake huron). A cold front that moved through
northern Michigan during the early morning hours now just south of
the state line. Confluent flow aloft across Michigan between
northwesterly northern branch flow to the north and anticyclonic
flow emanating to the east of a broad southern branch upper low
spinning over the Central High plains and rockies. Nice pocket of
dry air has settled across upper/northern lower Michigan this
afternoon...and with mixing dew points have dropped off as a result.

Surface high forecast to move into Quebec overnight...with a tighter
pressure gradient and stronger east/southeast boundary layer flow
developing. Ridging aloft will cross the state overnight as well.

Primary forecast concerns: minimal.

Tonight...another quiet night expected with just some high clouds
advancing from the southwest as upper level ridge axis crosses the
state. Winds should drop off initially this evening but as pressure
gradient tightens up overnight winds will swing around to the
east/southeast and pick up once again. Given dry air mass in place
and initially light winds expect temperatures to slip into the 30s
tonight most areas...some 20s across northwest Chippewa County where
afternoon temperatures are stuck in the upper 30s/40s thanks to
winds off the lingering Lake Superior Glacier.


Short term...(sunday through tuesday)
issued at 327 PM EDT Sat Apr 18 2015

High impact weather: minimal

Forecast challenge: timing of the rain Sunday into Sunday night.

(04/19)sunday...looking at the GFS the last few days, has been one
of a back and forth on whether the rain will get into east upper. One
or two 6 hour runs says yes, then on the 12z run no. Such is the
case, again although it didn't back off the rain entirely. Looking
at the 850 mb moisture, while the GFS has been fairly well in line
with the ECMWF, the quantitative precipitation forecast on the GFS has out run the European model (ecmwf). Seeing
that the low level moisture has been lacking due to the surface high
(today a Hudson Bay high) moving in and around the region this week.
So hedged closer to the sref mean idea, which seems a decent
compromise between the two, and for what it's Worth, the NAM is
about as slow as the European model (ecmwf). So the rain will arrive in north lower
probably after 21z and in east upper after 00z.

After 00z, the idea is pretty simple, the surface low rotates up over
Michigan through the night with a couple of 500 mb shortwave troughs
moving through the region at the same time. With the precipitable water of 0.75"
to 1.0" and the forcing with the system will expect that there will
be periods of rain through the night.

(4/19)monday...the rain should continue into the day as the 500 mb
low moving out of Manitoba and into the upper Great Lakes, however,
it will probably become more showery as dry air entrained aloft gets
pulled into the region ahead of the low. So have chance to likely
probability of precipitation as the moisture varies with time through the day.

Around 00z and there after, it looks like the 850 mb temperatures
fall enough that there will be a rain/snow mix that will last
through the night. Although, it could be all snow by day break,
albeit minor to light accumulations, as the 850 mb temperatures fall
to around -7c by 12z over North Lake Michigan.

(4/20)tuesday...the 500 mb low continues to spin over the upper Great
Lakes. This contributes to the GFS being about 2c cooler than the
ecmwf(00z), so will have a mix through the day as the surface
temperatures rise to the upper 30s to lower 40s, even in east upper.


Long term...(tuesday night through saturday)
issued at 327 PM EDT Sat Apr 18 2015

A stubborn...slow moving...500mb cutoff low over the Great Lakes and
Ontario will lead to below normal temperatures and some precipitation into
Friday. This cutoff looks to stay around through most of the weekend
before finally lifting into New England. With some weaker shortwave
energy passing overhead around the main low...chances for showers
will remain through most of the period. previously overnight temperatures could see some snow mixing in.

Things will begin to clear up through the weekend as the cutoff low
lifts...but an Omega block looks to be setting up by Saturday night
with another closed low in the Gulf of Alaska/northern Pacific and
broad high pressure over the Continental U.S.. situated squarely in the
descending/cold air advection side of this...we could be in for a stretch of dry
weather and below normal temperatures until The Block breaks down. European model (ecmwf) is
a bit stronger with this...but other guidance picking it up as


Aviation...(for the 00z tafs through 00z Sunday evening)
issued at 731 PM EDT Sat Apr 18 2015

VFR. Low level wind shear tonight.

High pressure just south of James Bay is maintaining a very dry
airmass...this will continue through tonight. On Sunday...the high
will move far enough east to allow a more moist...southerly flow
to develop. This will mainly result in increasing middle/high clouds.
Chances for rain and ceiling/visibility restrictions look to be a bit
slower to invade than earlier prognosticated...and for the most part
should hold off until just after this taf period.

East to southeast surface winds through the forecast...a bit gusty Sunday.
Low level wind shear tonight with strong southeast winds just off the surface.


issued at 327 PM EDT Sat Apr 18 2015

Tonight: pressure gradient builds tonight as high pressure builds
into Quebec and pressures fall across the plains. East/southeast
wind will increase overnight.

Outlook: small craft advisories likely for Sunday/Sunday night most
nearshore zones.


Apx watches/warnings/advisories...


Near term...jpb
short term...jsl
long term...alm

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