Area forecast discussion
National Weather Service Detroit/Pontiac Michigan
709 am EDT Thursday may 23 2013
Aviation...
//discussion...
Conditions will rapidly deteriorate to MVFR this morning as winds
turn northerly behind a cold front making its way through Southeast
Michigan. The front is currently between fnt and ptk and should pass
through ptk around 12z...and the metropolitan airports around 13z. Rain
showers could reduce ceilings to IFR at times as north winds gust to 20
knots. The front will continue moving south tonight...as approaching
high pressure brings dry air and VFR conditions to the taf sites
during the evening hours.
//Dtw threshold threats...
* high confidence in ceilings below 5000 feet by 13z...continuing
through the early evening hours.
&&
Previous discussion...issued 352 am EDT Thursday may 23 2013
Short term...today and tonight
A slowly sinking cold front will bring an abrupt change in
temperatures across Southeast Michigan today. In contrast to several
days approaching or exceeding 80 degrees...todays highs will only
get into the 50s across the north...with 60s expected across the
south. The highs realized today will occur in the morning
hours...before the push of cold air pushes afternoon temperatures
down into the 40s across the north and into the 50s across the
south. In addition to cooling temperatures...the front will bring
rain showers and a brisk north wind behind it during the afternoon.
Overall Southeast Michigan is in for a wet...windy and cool day with
the best weather occurring during the early morning hours.
The piece of good news today is the threat for thunderstorms appears
to have diminished to the Point of leaving thunder out of the
morning forecast as MUCAPE values struggle to get to 100 j/kg ahead
of the approaching cold front. Dynamics will be easy to come by
today as the low that has been out to our west for the past several
days tracks through the central Great Lakes as a positively tilted
trough with several embedded shortwaves as shown on the water vapor
imagery. A cross section through Michigan shows abundant moisture
and fgen from 925 mb to 850 mb as the cold front sinks
south...warranting categorical probability of precipitation as the front tracks through
Southeast Michigan today.
The front will push east early this evening as the middle level trough
becomes neutrally tilted and moves east with the front. High
pressure will bring dry air and quiet weather to the central Great
Lakes later tonight as 850 mb temperatures sink to around zero
degrees. With clearing skies and the push south of these cold
temperatures...some frost is possible away from the Great Lakes and
the Detroit metropolitan area as low temperatures fall into the middle to
upper 30s. Closer to the lakes and across the metropolitan area lows are
expected to get down to around 40. The main factor inhibiting
widespread freezing temperatures will be surface winds around 10 miles per hour
as a tight pressure gradient remains between the departing low and
the high building in from the north.
Long term...Friday through Wednesday
Fairly quiet weather through most of the extended forecast. A
blocking pattern...upper lows over both coasts...will set up across
the Continental U.S. For the Holiday weekend locking US under the eastern edge
of upper level ridge and directly under broad area of surface high
pressure. Pattern breaks down by middle week as East Coast trough gets
absorbed in northern stream flow and lifted into the Atlantic.
Meanwhile strong midlevel shortwave will shoot around the West Coast
trough and will begin to break down the amplified ridge. Only real
chance of precipitation will come Wednesday/Thursday as the short wave will attempt
to lift a warm front through the area.
Friday through Sunday will feature a cool dome of surface high
pressure building south from Canada with midlevel confluent flow.
Friday will start off on the breezy side as we fall on the eastern
side of the high under a decent NE/SW pressure gradient. The
persistent feed of cool air...850 mb temperatures in the single digits
through the day...will keep daytime highs in the low 60s which is
about 10 degrees below normal. The exception will be The Thumb
region where the onshore flow will keeps temperatures in the low/middle 50s.
Heights will gradually rise through the weekend. This combined with
clear skies and decreasing northerly flow will produce a warming
trend through the weekend by Monday.
For the middle part of the week...the aforementioned shortwave will
eject out of the West Coast trough and track up across the northern
plains into Ontario. This will lift a warm front up through the
Great Lakes bringing mild westerly/southwesterly flow back to Southeast Michigan
and allowing temperatures to jump back near 80. Models disagree with timing
of the frontal passage and amount of moisture associated with it so went with
low chance/slight chance probability of precipitation starting Tuesday night for the time
being.
Marine...
A cold front sinking south will cause winds to shift to the north
across all waters this morning...as the main surface low and
trailing cold front push off to the east. Winds and waves will
increase greatly with the advection of cold and dry air...leading to
Small Craft Advisory conditions for all of the Lake Huron nearshore
waters and Lake St. Clair. Further south offshore flow will cause
winds to stay below criteria for Western Lake Erie. Therefore will
continue and issue small craft advisories for these zones today and
tonight. Although winds may briefly reach gale force across Southern
Lake Huron this afternoon...the window appears brief enough and wind
speeds marginal enough to avoid hoisting gale warnings for this
afternoon. A continued north wind and long fetch along Lake Huron
will continue small craft conditions for the Lake Huron nearshore
zones and outer Saginaw Bay as waves remain elevated on Friday.
High pressure will bring lower winds and waves across the central
Great Lakes this weekend...with conditions expected to be well below
any headlines.
&&
DTX watches/warnings/advisories...
Michigan...none.
Lake Huron...
Small Craft Advisory...inner Saginaw Bay...until 8 PM Thursday.
Small Craft Advisory...nearshore waters from Port Austin to Port
Huron...until 6 PM Friday.
Small Craft Advisory...outer Saginaw Bay...until noon Friday.
Lake St Clair...
Small Craft Advisory...from noon Thursday to midnight Friday.
Michigan waters of Lake Erie...none.
&&
$$
Aviation.....Kurimski
short term...kurimski
long term....drk
marine.......kurimski
You can obtain your latest National Weather Service forecasts online
at www.Weather.Gov/Detroit (all lower case).
