Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Detroit/Pontiac Michigan
716 PM EDT Friday Mar 14 2014
A gusty pre-frontal southwest flow prevalent at the start of the taf
cycle will diminish in both magnitude and gust frequency as the cold
front slips through 02z-03z. Frontal passage will bring a wind
shift to west or west-southwest /250-270 direction/. Narrow pocket of middle
level cloud associated with the frontal passage during this time.
Upstream observations continue to support the east-southeast
expansion of lower stratus as colder air funnels in tonight. Low
VFR initially will settle into high MVFR through the early morning
hours. Low probability exists for light precipitation development
through this time, although the limited duration and coverage will
preclude a defined mention. Pocket of drier air trailing this
moisture will work to clear this cloud deck out by middle morning.
//Dtw threshold threats...
* medium confidence in ceiling below 5000 feet this evening...high
confidence tonight /after 04z/.
Previous discussion...issued 310 PM EDT Friday Mar 14 2014
Patchy passing high clouds have done little to filter sunshine
today...so maxes did overachieve by 5 degrees or so. Cold front
still tracking across Lake Michigan this evening...bringing some
light rain and lower clouds to northern Michigan. As the front
approaches lower Michigan...dry air will be difficult to overcome.
Expecting low chance of light rain or virga to be the confined to
the frontal zone in the 00-06z time frame. The more tangible effect
will be overcast clouds under 5kft that will combine with winds over
10 knots tonight. This setup will allow mins to remain a bit
higher...just under the freezing mark. Secondary cold front will
start to affect the Saginaw Valley closer to daybreak...and if front
timing speeds up (as models have trended) then mins will be a bit
cooler in our northern reaches. Could also see some flurries with
the addl cold air advection.
Long term...Saturday through next Friday
Upper wave over northern Manitoba will slide across the northern
Great Lakes Saturday...pushing associated surface low pressure well
to our east over southern Quebec by 12z. Cold front trailing the low
will continue to drop through the area during the first part of the
day. This could generate a quick light snow shower or some
flurries...but with just a quick shot of weak forcing and
increasingly shallow moisture...not expecting widespread
accumulations. Elevated portion of the front (925-850mb) will end up
settling near the Michigan/Ohio border late tomorrow...then sink
slowly southward both Saturday nigth and Sunday as high pressure
settles into the area. The high center shifting over northern
Michigan by Sunday will bring dry conditions for the remainder of
the weekend...and keep the Post-frontal shot of cold air entrenched
over the central Great Lakes.
With regard to maximum temperatures...not expecting impressive recovery from
mins Saturday morning as cooler air pours in behind the front. Highs
should generally be in the 30s. Sunday looks like a day we could
overachieve (above MOS guidance) with some middle-March
sunshine...similar to what happened on Thursday. H850 temperatures between
-10 and -16 will still keep temperatures much below normal however...and
kept forecast highs held to the upper teens in the northern thumb
and 20s elsewhere. Increased northeast winds Sunday as a low
pressure system tracks to our south will keep wind chills limited to
the single digits for most of the day. Mins both Saturday night and
Sunday will be unseasonably chilly...generally in the single digits
to low teens. Colder night will be Sunday night as winds decrease
and we see more clearing. These will not quite be record
readings...but we could get close at mbs (march 17 record low is 1).
Temperatures should rebound a little on Monday into the middle/upper 20s as
flow turns more southerly ahead of an approaching upper wave.
High pressure will slowly shift from the northern Great Lakes
eastward over Quebec by late Monday. Low pressure begins to build
across the Central Plains on Tuesday with a front bringing some
precipitation to the northern Great Lakes during the day.
However...Southeast Michigan is expected to remain dry until late
Tuesday night into Wednesday. There is still some uncertainty
regarding the timing and track of this system and therefore have
only kept chance probability of precipitation in the forecast Tuesday night through
Wednesday night. High temperatures will range from the middle 30s to
middle 40s through the extended period bringing maximum temperatures
closer to normal for this time of year /mid to upper 40s/.
Gusty southwest winds will persist over the area through this
evening as low pressure tracks across the northern Great Lakes. Wind
gusts will remain under 30 knots. Winds will then veer to the
northwest tomorrow behind a cold front trailing the system...and
remain on the gusty side until high pressure builds into the
northern Great Lakes Saturday night.
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).