Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 191128

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
728 AM EDT Sun Mar 19 2017


High amplitude mid to upper level ridging will build across the
region today. Subsidence invoked by the large scale height rises has
already been productive in clearing skies out down into the Tri
Cities and Thumb. Fog potential doesn`t appear good with daybreak
commencing. Question is how far south the the aggressive clearing
will make it before diurnal cloud development should fill clouds
back in. Continued to go more pessimistic in tafs with BKN MVFR.
High clouds will then be on the increase this evening with approach
of frontal boundary.


*  High in ceilings below 5000 ft this morning, Moderate this
   afternoon, low tonight.


Issued at 356 AM EDT Sun Mar 19 2017


A much quieter weather pattern is in store for southeastern Michigan
today as an incredible amount of 1000-500mb geopotential height
rises is ongoing across the state. Infrared satellite imagery this
morning supports the height rises are leading to very active mid to
lower level subsidence with a thicker stratus canopy over just about
the entire southern lower Michigan. Not complete clearing of skies
yet with high ambient moisture in the lower troposphere persisting
around the nuisance surface trough. Modeled MSLP suggests the
surface trough should have been nudged out of the area and latest
MSAS suggests that it is about to.

Today...All support for light showers, drizzle has been effectively
stripped out. Expect dry conditions today. Real question centers on
cloud trends. Model data, both the 4km and RAP depicts very
aggressive subsidence punching down and subsaturating the 1.2 to 6
kft agl layer. Given the evidence this is already occurring
confidence is higher that we will see sunshine today. The only
question is timing. Pattern recognition suggests to hold onto cloud
a little longer this morning with decreasing clouds this afternoon.
With that stated there will be some high cloud pushing southward
into the area by towards evening in advance of the approaching weak
cold front. Lack of any gradient will keep relatively colder air in
at the surface. This will lead to both a very stable lake aggregate
setup today along with temperatures holding in the lower to middle

Tonight...Apex of the 500-300mb ridge axis is forecasted to be in
place overhead through 06Z then pushing east of the region between
06-12Z. Any lead shortwave energy is shown to advect eastward north
of the northern Great Lakes, with an actual coherent subsidence
anticyclonic vorticity structure tumbling across southeastern
Michigan the latter half of the night. Moisture will increase and
lapse rates will steepen between 08-12Z across the northern cwa,
however, the preference is to really hold onto a dry forecast before
12Z. Precipitation probability tendencies are decided in more
negative trends for any precipitation prior to 13Z.

Monday...Col structure and very weak cold front is forecasted to
track south southeastward through the cwa during the day. Dynamical
support for ascent will be tied to what is actually an impressive
mix of 850mb moisture transport and 500mb theta e ridge. Forecast
isentropic RH analysis suggests that modeled moisture over the
southern half of the cwa primarily for the 14-20Z window is more
favorable than what past model runs have been showing. The forecast
is carrying likely PoPs which is reasonable. Sounding structure of
fronts is favorable for an elevated convective response with low
static stability aloft under neutral lapse rates. Could be a sneaky
QPF type scenario. Lack of strong PV advection with poor Showalter
support precludes a thunderstorm mention.

Tuesday...Aggressive surface ridging is forecasted on the back of
low level cold air advection at the synoptic scale. The 850mb cold
front with 850mb temperatures as cold as -14C will backdoor
southward across the area Tuesday evening. A very classic early
spring response that will usher in a very cold air mass. In fact,
low temperatures Tuesday night could fall back into the teens to
lower 20s.

Winds will be fairly light today and tonight as high pressure slides
across the area. Modest southerly winds will develop late tonight
into Monday as low pressure tracks into Hudson Bay. This system will
pull a cold front through the Central Great Lakes Monday afternoon,
bringing a wind shift to the northwest. The somewhat gusty northwest
flow that this cold front brings will extend through Wednesday.


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



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