Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 191429
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1029 AM EDT Fri May 19 2017

.UPDATE...

MCV is showing up nicely on satellite and radar imagery over
Illinois this morning. This feature is forecast to lift through the
Ohio Valley and Southern Michigan this afternoon/evening. Last
several runs of the HRRR have had the best handle on precipitation
being generated by this feature and what`s still left over from last
night. Hard to judge how much of this activity will survive as the
MVC works northeast later today. IR satellite imagery shows cloud
tops associated with the convection rapidly warming. Additionally,
remnant activity will be encountering very dry mid-level air and
ridging building over Michigan. For this reason, forecast update
limited pops to the chance category with only light rain amounts
forecast.

&&

.PREV DISCUSSION...
Issued at 616 AM EDT Fri May 19 2017

AVIATION...

MVFR stratus has been drifting southward through the early morning
hours as cold air funnels into the region across Lake Huron. CIGS
will slowly lift through the early afternoon before drier air helps
scour out the low stratus. Higher clouds will slide in this
afternoon associated with the large convective complex lifting
northeast out of the plains. All the while, northerly winds will be
veering to the northeast but remaining below 10 knots for the most
part. CIGS will lower once again on Saturday as the next low
pressure system lifts into the region with an attendant warm front.
Showers could begin as early as Saturday afternoon.

//DTW THRESHOLD PROBABILITIES...

* High for ceilings below 5kft this morning. Low for tonight.

PREV DISCUSSION...
Issued at 355 AM EDT Fri May 19 2017

DISCUSSION...

Strong cold air advection across the lowest 925 mb well underway
early this morning, the process now augmented by an additional
marine contribution under increasingly northerly flow.  This inbound
air mass will present a significant downward trend in the overall
thermal profile for today, as 925 mb temperatures hold in the single
digits. Recent satellite trends in conjunction with model sounding
data also suggest some degree of low stratus will exist for at least
the morning period, before gradually diminishing in coverage as drier
air mixes in during the latter half of the day. Under a prevailing
northeast gradient, this all works to minimize the overall diurnal
response and limit highs to within a couple degree of 60F. Existing
ambient moisture depth appears too lean to support shower production
today. However, downstream evolution of the extensive convection now
lifting into Missouri will be closely monitored, as the potential
does exist for a MCV supported complex or clusters to maintain some
integrity as they lift toward the lake Michigan corridor. Local
environment certainly much less supportive relative to points
upstream, but still plausible some remnant showers survive into lower
Michigan by late afternoon/evening.

Attention then turns to the closed mid level system currently
centered over the central rockies.  This system remains projected to
lift northeast through the upcoming weekend, reaching western lake
Superior by Sunday.  Standard low-mid level response immediately
downstream as this process unfolds, with deepening southwest flow
establishing a broad warm conveyor belt preceding the attendant cold
front.  Lead wing of moist isentropic ascent working across the
existing 850-925 mb warm frontal slope will struggle against a
residually dry deep layer profile on Saturday.  This continues to
cast doubt as to potential precipitation chances during the daylight
period.  Surface warm front holds well to the south, ensuring cooler
easterly flow remains locked in locally throughout the day. General
air mass modification as upper heights briefly climb will ease highs
into the 60s.

Best rainfall potential centered Saturday night/early Sunday, driven
by a combination of increasing height falls, frontal forcing and
strong theta-e advection.  Diminishing mid level stability will be
conducive for elevated thunder as well.  Retention of a high degree
of stability across the lowest 2-3 kft will minimize the potential
of witnessing more organized convection, simply some heavier
rainfall possible at times as the main moisture axis pivots through.

Moisture axis looks to outpace the actual frontal passage by several
hours on Sunday, providing a window for modest pre-frontal recovery
during the daylight period.  Actual frontal timing likely dictates
whether a secondary period of development occurs at the frontal
interface before lifting into Canada.   A moderately mixed southwest
gradient will work off from a relatively mild morning temperature to
lift readings into the 70s.

Consolidation of the aforementioned closed low with shortwave energy
of northern Canadian origin will establish broader longwave
troughing over the north-central conus during the early-mid week
period.  This will maintain a cooler pattern, although with
temperatures currently progged to reside just below normal for mid
May /mid-upper 60s/.  Potentially unsettled as well, particularly
Tuesday into Wednesday as a piece of the main wave breaks off and
pivots into the region.

MARINE...

Northerly winds remain gusty in the wake of a cold front dropping
though the southern Great Lakes. Long fetch will build waves across
the southern Huron basin resulting in small craft advisories
continuing into this afternoon. Winds will weaken some later in the
day while becoming more northeasterly as high pressure slides across
Ontario. Winds will continue to veer through easterly Saturday
becoming southeasterly Saturday night as the next system, and warm
front, lifts into the region.

HYDROLOGY...

Low pressure will lift across the Upper Midwest this weekend
bringing showers and thunderstorms over the area late Saturday
through Sunday. Total rainfall looks to average in the 0.5 to 1.0
range, with higher totals expected in places where thunderstorms
occur.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory until 4 PM EDT this afternoon for LHZ421-422-
     441>443.

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

$$

UPDATE.......HLO
AVIATION.....DRK
DISCUSSION...MR
MARINE.......DRK
HYDROLOGY....DRK


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