Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Detroit/Pontiac Michigan
636 am EST Friday Mar 6 2015
Southwest return flow will strengthen through the day as the
gradient strengthens between approaching upstream low pressure and a
high over the eastern US. Sustained winds will hover between 10-15
knots with gusts near 20 kts during peak heating. Scattered cumulus around 3kft
is possible during the day but coverage is expected to remain
limited. Deeper moisture will move in overnight causing ceilings to fall
below 5kft after 00z before deteriorating to MVFR after midnight.
//Dtw threshold probabilities...
* low for ceilings below 5kft today. High after 00z.
Previous discussion...issued 305 am EST Friday Mar 6 2015
Short term...today and tonight
High pressure draped across the southeast United States coupled with
low amplitude northwest flow aloft will facilitate persistence of
dry conditions through the forecast period and a continuation of
southwest gradient flow. Ongoing light warm advection will warm
925mb temperatures by 10 or more degrees over the next 24 hours,
ensuring high temperatures in the middle 20s, or about 5 to 10 degrees
warmer than yesterday. More potent energy located well upstream will
encroach on the Great Lakes overnight. Strengthening southwest
gradient will force a gradual rise in temperatures overnight. No
arguments from 00z guidance that indicate temperatures bottoming out
around 20 early before rising back into the middle 20s by sunrise
Saturday. Nothing more than episodic middle/high clouds expected
through the daylight hours before better low-level moisture lowers
the cloud deck after sunset.
Lower amplitude middle level northwest flow will define conditions
locally through the upcoming weekend. Weak shortwave energy
originating from the Gulf of Alaska will shear into this flow over
the next 48 hours...translating across Southeast Michigan on Saturday.
Corridor of warm air advection will emerge immediately in advance
of the height falls...prompting a solid upward adjustment in
temperatures relative to today. Extensive cloud cover will dampen
the response to some degree...but a modestly mixed environment
through 925 mb /-2 to -3c/ supports highs of middle-upper 30s. Brief
shot of isentropic ascent on the front end and a late day cold
frontal passage warrants a low end pop mention throughout the
day...but the limited moisture quality and lackluster forcing will
seemingly restrict precipitation chances. Ensuing weak cold air
advection into Saturday night...the process perhaps yielding a few
flurries as moisture briefly deepens with the passing 850-925 mb
frontal slope. This frontal zone will temporarily settle just to
the south by Sunday morning...providing a window of opportunity
for some clearing overnight. Going forecast leaning toward the
colder end of guidance for lows Sunday morning...latest model
evidence providing little evidence to move away from this position
/upper teens to lower 20s/.
Frontal zone will wash back eastward and across Southeast Michigan on
Sunday as the mass fields reorient again with the approach of
another weak shortwave. Clouds will likely remain problematic
accounting for both the frontal passage and a brief uptick in cva with the
shortwave itself. Once again...moisture will be lacking to suggest
anything more than a lower end probability for a few snow showers to
develop. A moderating thermal profile will again support highs of
The existing troughing will ease early next week...increasing depth
to the low level west-southwest flow establishing a firm period of
warm air advection. The magnitude and duration of this warm up
still carries some uncertainty yet at this time scale...00z GFS
considerably more progressive with the next inbound height fall
center and stronger frontal passage /Wednesday/ relative to the
European model (ecmwf) and Canadian /following weekend/. Regardless...looking at a
stretch of seasonable conditions through at least the midweek
Southwest flow will strengthen today throughout the central Great
Lakes. A firm southwest gradient reaching 25 to 30 knots will exist
across portions of Central Lake Huron this afternoon and early
evening. This will bring the potential for a brief period of
gales. However...the combination of a limited duration...marginal
magnitude and the fact that a majority of the lake remains ice
covered will preclude the issuance of a Gale Warning for today.
Pressure gradient will ease into tonight...with the arrival of
warmer air providing an increasing stable environment heading into
the weekend. Modest southwest flow in place Saturday in advance of
a cold front. Weak surface ridging then yields a weaker westerly
flow for Sunday.
Lake St Clair...none.
Michigan waters of Lake Erie...none.
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