NWS Forecast Discussion

000
FXUS63 KDTX 230352
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1152 PM EDT Sat Apr 22 2017


.AVIATION...

A ridge of high pressure will extend across srn Lower Mi into early
Sunday afternoon. Strong mid level subsidence and abundant dry air
combined with this sfc high will sustain tranquil aviation
conditions into Sun afternoon. A cold front will then accelerate
southward across Lake Huron late in the day, advancing into MBS
toward early evening and into metro Detroit around 06Z Monday. The
front will be marked by an abrupt wind shift to the northeast.

//DTW THRESHOLD PROBABILITIES...

* none

&&

.PREV DISCUSSION...
Issued at 337 PM EDT Sat Apr 22 2017

DISCUSSION...

High pressure over the Central Great Lakes will continue to provide
quiet weather tonight into Sunday. Large scale subsidence will
overtake the area tonight as shortwave ridging expands into Lower
Michigan, providing clear skies overnight after cirrus exits. Calm
winds, clear skies and temperatures falling into the 30s will
provide a good chance for frost formation across the area and will
issue a frost advisory for counties along and south of the I-69
corridor. This is where the growing season has already progressed
far enough for frost to damage sensitive vegetation. The exception
within the advisory will likely be over the more urban areas of
Metro-Detroit, particularly in Wayne County, and along the shoreline
of Lake Erie in Monroe County where temperatures where stay a little
warmer. Only element of uncertainty for the remainder of the
advisory area will be moisture recovery overnight. Dewpoints have
only fallen into the low/mid 30s this afternoon as flow remains off
Lake Huron and soils remain more moist than over the rest of the
State from recent rainfall. Enough moisture for frost formation is a
concern, but confidence is higher in Southeast Michigan than for the
remainder of Lower Michigan.

Upper energy dropping through Central Canada will meanwhile push
surface low pressure across Ontario and Quebec, with surface
troughing brushing across the Northern Great Lakes tonight into
early Sunday. This will push a pretty strong cold front down into
Northern Michigan and Lake Huron. The front will mark the
delineation between cooler and cloudy conditions on the north side,
and much more mild and pleasant conditions on the south side. The
front will only settle slowly to the south through the day on Sunday
as it loses upper support and becomes parallel to flow aloft,
stalling near or just north of the extreme northern portion of the
forecast area. Sunny skies with max temperatures well into the 60s
remain in the forecast for Southeast Michigan, but will watch to see
if front could progress slightly further south into
Bay/Midland/Huron counties. Lake Huron could aid in this, as the
cold waters will do little to impede the surface front.

High pressure will become suppressed to our south and east late
Sunday night into Monday. This may allow the cold front poised just
to our north to progress into south-central Lower Michigan
overnight, before low pressure approaching from the Plains and Upper
Midwest lifts it back northward again. Overall, expecting not much
change in sensible weather from Sunday to Monday, other than some
increasing clouds late.

One of the changes in the long-range forecast compared to
yesterday`s 12Z suite is the lack of upper-level disturbances that
were expected to perturbed across the Great Lakes through Tuesday.
As a result, conditions are expected to remain dry throughout the
day on Tuesday, although cloud cover will gradually increase from
morning into evening, with overcast skies expected nearing sunset
and into the overnight hours. A weak low, pushing in from MO into
the Great Lakes Wednesday into Thursday, will veer winds from SE to
SW Tuesday into Wednesday, allowing daytime temperatures to peak in
the low to mid-70s as warmer air is advected into the region. A cold
front dragging behind the low will also bring the chance for rain
showers and thunderstorms, however, model solutions continue to
diverge regarding the timing of the front.

The GFS drags the cold front through as early Wednesday morning into
early afternoon (which would limit the possibility or at the very
least the extent of seeing 70s through the afternoon), while both
the GEM and ECMWF model runs push the front through late Wednesday
into Thursday morning. In any case, confidence remains moderate to
high regarding the chance for rain Wednesday into Thursday, however,
confidence is low regarding timing of rain and potential
thunderstorms.

Additional chances for rain and potentially thunderstorms Friday
into Saturday, however, models continue to diverge on potential
solutions, so PoP values will remain sub-50 heading into the weekend
until better convergence is seen. Tweaking of daytime highs and lows
will also be possible as stark contrasts can be seen regarding
WAA/CAA over the weekend. For example, GFS puts 14C temperatures at
850 mb on 18Z Sat while the GEM run exhibits -5 C at the same time.

MARINE...

High pressure will maintain favorable marine conditions into tonight
as it settles slowly south of the area. Southwest flow will increase
slightly late tonight on the northern periphery of this high, but do
not expect gusts any higher than 20 knots or so. A cold front will
bring a quick shift to north winds on Sunday over Lake Huron. Flow
will then back to the east Sunday night into Monday. Gusts will once
again increase and range between 20 and 25 knots on Monday, mainly
over far northern Lake Huron.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Frost Advisory until 8 AM EDT Sunday for MIZ060>063-068>070-075-076-
     082-083.

Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&

$$

AVIATION.....SC
DISCUSSION...HLO/AM
MARINE.......DG


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NWS DTX Office Area Forecast Discussion