Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Detroit/Pontiac Michigan
314 am EST sun Jan 25 2015
Short term...today through tonight
The short term period will be dominated by the influence of high
pressure currently centered beneath an area of confluent flow
aloft and centered over far northwest Ontario. Northeast winds
around the periphery of this high have begun to fill into
Southeast Michigan behind the cold front that is making its way
through the County Warning Area. At 07z, temperatures were in the middle 20s north of
I-69 with middle 30s to the south. The front will reach the Ohio
border around sunrise. Ongoing cold advection is forecast to drop
925mb temperatures from around -2c ahead of the front to -12c
behind the front by this evening. As a result, high temperatures
will occur in the morning at all locations. Insolation will help
falling temperatures level off around 20 degrees this afternoon.
Low-level dry advection will increase markedly this afternoon into
this evening as high pressure builds into Ontario. This is expected
to favor an an erosion of low clouds from east to west during the
day. Light snow showers are likely near the Ohio border as the 850 mb
front sags to the south and contracts a bit in advance of a system
traversing the Ohio Valley today, but prospects for measurable
precipitation are rather low. At this time, left likely probability of precipitation confined to
only the far south where a couple tenths of accumulation will be
possible. Clearing tonight and an easing of the gradient within the
fresh Canadian airmass will allow temperatures to fall into the
single digits by Monday morning.
Long term...Monday through Saturday
Colder weather will persist into early next week as passing clipper
phases into major East Coast storm and upper trough over the eastern
Continental U.S. Deepens in the process. Highs on Monday still look to hold at
20f of below with lows in the single digits to lower teens. Heights
do begin to rise by Tuesday as upper trough shifts east as strong
low pressure system wraps up along the eastern Seaboard. This will
allow for temperatures in the middle/upper 20s. During this time frame
only a few passing flurries as expected as shortwave energy digs
into the developing upper trough...namely in the Monday night time
Temperatures gradually moderate into the Wednesday and Tuesday
period as main upper trough axis shifts off the East Coast and
heights over the area rise rather as shortwave ridge builds into the
area in advance of next notable clipper system. This will bring back
into the 30s during the middle of the week. This clipper will also
bring the next chance of precipitation...mainly snow...by Thursday.
Once this system passes...colder weather will again settle in over
the Great Lakes from late week into next weekend as southern edge of
a more significant Arctic airmass builds into the northeast Continental U.S..
additional snow shower chances can also be expected as a number of
shortwaves race through the area along this boundary by the end of
this forecast period. Highs will once again fall back closer to 20f
with lows back into the single digits.
North flow over Lake Huron...behind a passing cold front...will veer
to the northeast today and tonight as high pressure shifts across
Ontario. Winds will increase with the colder unstable air...but will
remain below 30 knots today and then decrease this evening into
While northeast winds will gust to near 25 knots today over the near
shore waters...extensive ice cover will prevent any of the typical
wave issues associated with moderate onshore flow...
craft advisories will not be needed. Early next week...conditions
will remain relatively calm with wind gusts remaining at or below 20 knots
over the Lake Huron open waters as several high pressure centers
build across the area.
Aviation...issued 1156 PM EST Sat Jan 24 2015
Cold frontal boundary will settle southward across the region early
this morning. This will bring a wind shift to the northeast. This
process will sustain a broken canopy of stratus through the morning
period. Some variability to ceiling heights as this process unfolds
will leave conditions fluctuating between high MVFR and low VFR
through this time. Limited potential for light snow showers to
emerge with this front across the Detroit corridor Sunday morning
before it settles southward. Southeast Michigan will remain north of the
main swath of snowfall attendant to low pressure tracking across the
Ohio Valley on Sunday. Drier air working in from the north will
favor a gradual clearing of any lingering lower stratus from north
to south through the day.
//Dtw threshold probabilities...
* high in ceilings below 5000 feet through Sunday morning.
Lake St Clair...none.
Michigan waters of Lake Erie...none.
You can obtain your latest National Weather Service forecasts online
at www.Weather.Gov/Detroit (all lower case).