Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 160444
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1144 PM EST Fri Feb 15 2019


.AVIATION...

After a clearing trend earlier this evening, MVFR based strato cu
have been rapidly expanding back across Se Mi as the low level flow
turns more northwesterly, ducting under a deep low level inversion.
Subtle low level cooling within the northwest flow has only
deepening the inversion. During the course of the morning, the low
level flow will turn more northerly and become increasingly more
divergent as high pressure expands into the northern Great Lakes.
This flow, with a less direct lake influence, is likely to allow
some breaks to develop during the morning. Persistent low level
anticylonic flow, subsidence, and a boost from diurnal mixing is
expected to finally scour our much of the strato cu field late Sat
morning into early afternoon.


.DTW THRESHOLD PROBABILITIES...

* Moderate in ceilings below 5000 ft Saturday morning.

&&

.PREV DISCUSSION...
Issued at 351 PM EST Fri Feb 15 2019

DISCUSSION...

Strong upper level PV associated with the low pressure system will
continue to pivot further to the east into Quebec this evening. Cold
air advection behind the morning cold front will keep windy
afternoon conditions going into the early evening supported by steep
lapse rates and strong low level winds mixing to the surface. Winds
gusting up to around 25-35 mph will begin to decrease through the
evening as the pressure gradient and lower level wind fields weaken
with the incoming high pressure. Dry air, lowering convective
depths, and veering of lower level winds towards the NW has brought
an end to the light snow/flurry activity off Lake Michigan seen
earlier in the day. Fair amount of sunshine has broke out this
afternoon, but anticipate some degree of cloud cover to return over
southeast Michigan and mitigate aby drastic drop in temperatures
overnight. This will hold lows tonight in the teens. Even as winds
begin to weaken, wind chills will drop into the positive single
digits to around 10 degrees this evening and remain in the single
digits overnight.

Sprawling surface high pressure centered across the northern plains
will push some height rises into southeast Michigan. The result will
be quiet weather on Saturday with dry and more stable conditions
under the cold northerly flow. High temperatures will come in
several degrees below normal in the mid to upper 20s with 850
temperatures around -8C to -10C overhead.

Main focus for Sunday will be the potential for light snowfall
arriving by Sunday afternoon. Broad and disorganized troughing over
the western US will carry a piece of energy originating over the
Pacific across the Rockies. This will lead to the development of a
mid level low and surface troughing across the plains. This mid
level energy will be ushered eastward on the northern periphery of a
very strong southern stream jet core that extends from West Texas
through the Ohio Valley. Mid level flow will turn southerly bringing
subtle warm/moist air advection into Lower Michigan ahead of the
approaching low pressure. The mid level front and weak lift should
be able to support slight chances for snow as lower levels become
better saturated and remain below the freezing mark. Considering
fairly weak overall lift with this system, snowfall totals should
remain light with accumulations around an inch or less possible.
Higher totals will be focused along the MI/OH border given the track
of this system and where better forcing will reside. High
temperatures remain below normal in the 20s with little change in
the surface airmass.

Relentless pattern of anticyclonic wave breaking over the NPAC & CWB
over the NATL domain will continue for the duration of the extended
period courtesy of a retracted Pacific jet and active STJ extending
across the USA. This will, at least, result in stagnation of the
current pattern but will more likely favor some degree of longwave
amplification accompanied by a tendency for retrogression of the
mean storm track when energy occasionally ejects from the western US
trough. The forecast is therefore one that migrates toward
increasingly mild outcomes with time. The best chances for snow will
require suppression from the polar jet which will in turn limit
amplification potential and subsequent impact potential while deeper
cyclones will be far more likely to track west of the area and bring
snow-mix-ra transitions. The first manifestations of this tendency
are Sunday`s suppressed low-impact snow potential (discussed above)
followed by 12z NWP depictions of a warmer STJ-influenced system
lifting west of the CWA mid-week next week.

MARINE...

Northwest gales will continue over northern portions of Lake Huron
as a frontal boundary drops south through the area in the wake of
exiting low pressure. A Gale Warning will remain in effect until 10
PM this evening. Further south, westerly winds will steadily ease
into the evening and Gale Warnings over southerns parts of the lake
will be allowed to expire.

Winds will then drop off overnight and especially on Saturday as
high pressure arrives and builds through the region. Moderate
easterly winds then look to develop on Sunday as low pressure tracks
along the Ohio Valley river. Winds flipping around to the northwest
behind this low for early next week.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&

$$

AVIATION.....SC
DISCUSSION...AA
MARINE.......DG


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