Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
FXUS63 KDTX 241931
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
331 PM EDT Mon Apr 24 2017
Dry airmass remains in place (PW value of 0.27 inches per 12z DTX
raob) leading to above average diurnal swing, as temperatures reach
70+ degrees this afternoon away from Lake shadows.
Large upper level low over the Southeast Conus will pull back some
Atlantic moisture into the Central Great Lakes Tonight into Tuesday
morning, with PW values approaching 1 inch. A weak upper wave and
associated 6 hr pressure falls to move over southern Lower Michigan
around 12z Tuesday, but still does not appear sufficient to generate
showers, with SREF weighted probabilistic guidance still only
indicating pops above 15 percent but under 30 percent, and
preference will be to maintain dry forecast for majority of
southeast Michigan, with just slight chance across the Thumb Region
Tuesday morning. Moistening of the low levels and mid level clouds
will level out our warming trend for a day, as maxes likely only
peak near 70 degrees.
Amplifying upper level trough west of the Mississippi River Valley
as copious amount of upper level energy off the coast of the Pacific
Northwest moves onshore. Surface low progged to move into Iowa and
then into western Wisconsin on Wednesday, with thermal ridge axis
over southeast Michigan, as 850 mb temps rise into the mid teens,
with 700 mb temps up in the high single numbers. 12z NAM soundings
showing very strong CAP (CINS in excess of 100 J/KG), and expecting
a dry day with temperatures peaking out around 80 degrees as surface
winds swing around to 180-200 degrees late in the day. If the cap
does not hold for some reason, marginal risk of severe with MLcapes
in excess of 1000 J/kg and 0-6 km of bulk shear of 40 knots or
greater, especially if influence of Saginaw Bay comes into play and
the warm front gets hung up near Tri-Cities region, which looks
doubtful at the moment.
Second low pressure system coming out of the southern Plains,
lifting past St. Louis Wednesday evening, but system taking on
negative tilt may prevent showers/thunderstorms from arriving until
Thursday, supported by both the 12z Canadian/EURO and NAM solutions.
While discrepancies continue to exist regarding the track of
Thursday`s low, low pressure will likely drag a cold front behind it
Thursday morning into Thursday afternoon, providing enough lift see
rain showers and possibly thunderstorms along the front. Most places
are expected to stay relatively dry through Friday morning and
afternoon as temperatures remain more moderate with daytime highs in
the mid to upper 60s. A warm front is then expected to push north
into southern Michigan starting Friday afternoon into evening, which
will bring the slight chance to see pop-up rain showers.
This weekend looks to be a fairly active one as the advent of warmer
air and a series of low pressure systems brings the likely chances
for rain and possible chances for thunderstorms. A weak low pushing
from MO/IA into the Lower Peninsula will bring the low chances for
rain throughout Saturday. The better chance for rain will exist
throughout Sunday as the low pushes northeast from ArkLaTex into the
Ohio Valley. Thunderstorm chances will also be possible Sunday as
the GFS and ECMWF runs place SE MI in the warm sector. Thunderstorm
chances will continue into Monday as the low looks to drag a cold
front through Michigan.
A long duration of moderate southeasterly flow will exist through
Wednesday as the region remains between exiting high pressure and
low pressue lifting into the Mid Mississippi Valley. Sustained wind
of 15 to 20 knots at times, but with a higher degree of stability
under this pattern limiting the gust potential. Winds turn
southwesterly as low pressure lifts into great lakes on Thursday.
Issued at 1246 PM EDT Mon Apr 24 2017
Modest easterly flow will exist through the latter half of the day,
sustained south of high pressure. Intermittent gustiness to this
wind may emerge at the height of peak heating, but with gusts below
20 kts. Otherwise, this dry and stable environment will yield a
clear sky through the evening period. Extensive canopy of mid cloud
tied an expanding area of Atlantic moisture will pivot northwest and
into the southeast Michigan airspace overnight. This will bring an
increasing ceiling at 6 to 8 kft. There is at least some potential
for a lower ceiling to emerge by Tuesday morning /low VFR to MVFR/
depending on the degree of moisture transport, but confidence in
this evolution remains low at this time.
For DTW...Persistent east-northeast wind will continue to support
northeast operations through this evening. Mid cloud thickens
overnight and Tuesday morning, likely carrying cigs in the 6 to 8k
ft range...at least initially. Low confidence on a subsequent drop
in ceiling heights below 5000 ft with time through the morning.
//DTW THRESHOLD PROBABILITIES...
* Low for ceiling at or below 5000 ft late tonight and Tuesday
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
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