National Weather Service Raw Text Product

Displaying AFOS PIL: AFDDTX Received: 2019-03-20 07:20 UTC


873 
FXUS63 KDTX 200720
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
320 AM EDT Wed Mar 20 2019

.DISCUSSION...

NEAR TERM / TODAY THROUGH TONIGHT

As of 320 AM EDT...The first early morning of spring (although 
technically does not start until around 6pm this evening) continues 
to start off quiet across the region as surface high pressure 
continues to slide eastward into the Mid-Atlantic region/New 
England. Generally clear skies across the region will gradually give 
way to increasing cloud cover as the morning progresses ahead of two 
pieces of energy approaching from the west.

One piece of energy will be associated with a northern stream wave 
diving south from the northern Great Lakes, which continues to look 
fairly robust on water vapor satellite imagery. This feature will 
interact with a piece of shortwave energy ejecting out of the 
central Plains, with water vapor imagery also depicting a compact 
circulation associated with this feature. The end result will be the 
development of a weak surface low that tracks northeast across lower 
Michigan later today as the upper-level PV anomalies phase. 
Increasing midlevel height falls will result in a modest 
low/midlevel mass adjustment as a LLJ increasing to around 40 knots 
helps transport increasing moisture over the region as PWAT values 
increase over 0.50 inch. Isentropic analysis depicts modest ascent 
in the 1000-700 hPa layer, but bulk of dynamic lift will correspond 
to arrival of height falls this afternoon/evening.

Hi-res and local probabilistic guidance are in good agreement with 
precipitation holding off until after 1pm, with temperatures warming 
well into the 40s and even near 50 across portions of the Detroit 
metro resulting in precipitation falling as rain. Coverage looks to 
be widespread, especially from 3pm-8pm when the bulk of the rain 
will fall. Overall intensity will generally be light in nature, with 
best coverage of more moderate rain elements focused north of the M-
59 corridor. For more on expected rainfall amounts, see the 
Hydrology section below. 

In addition to rain today, southwest flow will strengthen and become 
gusty at times during the afternoon, with peak gusts 20-30 mph. Rain 
will transition to more of a showery nature this evening as the 
northern stream trough axis swings through. As the boundary layer 
cools with loss of daytime heating, a few wet snowflakes will mix in 
at times, especially north of the I-69 corridor. Not expecting much 
in the way of accumulation with any wet snow activity outside of 
maybe a dusting on some grassy surfaces. A weak cold front will move 
south across the region tonight with winds becoming northwest in its 
wake. Cold air advection will be minimal with the frontal passage 
(850 hPa temps falling from -2 to -4 C) helping to keep low 
temperatures at bay and settling in the low/mid 30s.

SHORT TERM / THURSDAY THROUGH FRIDAY NIGHT

Deepening longwave trough over the eastern seaboard will result in 
north/northwest flow setting up aloft during the day Thursday. 
Shortwave ridging and strong anticyclonic vorticity advection will 
ensure that Thursday is dry with high temperatures in the 40s. 
Trailing shortwave energy will race south through the mean longwave 
trough Thursday night into early Friday morning, and will brush 
eastern areas (particularly the Thumb) with scattered rain/snow 
showers. 00z GFS/ECMWF are a little more aggressive with coverage, 
with daytime heating during the day Friday potentially resulting in 
activity lingering into the afternoon hours. The trailing wave will 
usher in a brief period of colder temperatures Friday as the low-
level thermal trough swings through. Highs look to only reach the 
upper 30s for most areas, with lower 40s possible closer the Ohio 
border.

LONG TERM / SATURDAY THROUGH TUESDAY

Highly amplified ridging will then set up over the Great Lakes and 
Midwest for the weekend, with southeast Michigan residing on the 
eastern edge of the ridging. This placement will ensure dry weather 
with abundant sunshine throughout much of the weekend. Building 
heights/thicknesses aloft will allow temperatures to rebound, with 
highs Saturday back in the 40s, with upper 40s to lower 50s Sunday. 
Ridging will break down late Sunday into Sunday night, with the 
potential for precipitation along a developing cold front that will 
sag south across the region. GFS continues to be more aggressive 
with coverage, while the ECMWF remains drier. Given the overall 
synoptic setup across North America, which looks to feature a quasi-
Omega block pattern over Canada with strong high pressure moving 
from Manitoba into the northern Plains/Great Lakes, will side with 
the ECMWF solution as this pattern should favor the bulk of 
available moisture remaining south of the region. Aforementioned 
high pressure then becomes established over the region for early/mid 
next week with seasonable temperatures.

&&

.MARINE...

A low pressure system will settle across the region through tonight. 
Moderate southwest winds will exist today locally in advance of this 
system. Gusts 20 to 25 knots at times. A diminishing gradient as 
the low passes through will allow winds to ease tonight. Modest 
winds Thursday, before strengthening from the northwest Thursday 
night. Strongest northwest winds noted Friday, when a period of 
gusts to low end gales will be possible. Expect ice breakup to 
continue with the changing wind conditions and relatively mild 
weather.

&&

.HYDROLOGY...

Light rain will overspread the region this afternoon and evening. 
Rainfall totals of two to four tenths of an inch are expected. Most 
mainstem river levels have subsided significantly over the last 
several days. The additional precipitation will only serve to slow 
the steady decrease with no additional river flooding expected. 
Susceptible collection areas, that likely already contain run-off 
water, will swell with the additional precipitation.

&&

.PREV DISCUSSION...
Issued at 1146 PM EDT Tue Mar 19 2019 

AVIATION...

The onset of nighttime cooling will lead to a clearing of the 
remnant diurnal cu field over the next couple hours and will lower 
the south-southwest winds speeds around/shortly after sunset. Se Mi 
will remain under the influence of departing sfc high pressure 
through the night. So other than a few high clouds, this system will 
sustain clear skies into early Wed morning. A deepening low pressure 
system will advance into Lower Mi Wed afternoon/evening. This system 
and its associated moisture transport will allow widespread rain, 
with steadily lowering ceilings, to advance across Se Mi during the 
course of the afternoon Wednesday. 

DTW THRESHOLD PROBABILITIES...  

* High in ceilings below 5000 ft late Wed afternoon and evening. 

* High in precip type being all rain Wed afternoon and evening.


&&

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

$$

DISCUSSION...IRL
MARINE.......MR
HYDROLOGY....MR
AVIATION.....SC


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