Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 200402
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1202 AM EDT Sat Apr 20 2019


.AVIATION...

Cold surface flow has resulted in high static stability through
10kft agl. Given moist conditions, classic setup for laminar stratus
overnight. Shortwave ridging has broken down to allow light
overrunning precipitation to infiltrate far southeastern sections of
the cwa. Coupled upper level jet structure will allow elevated theta
e ridge to backdoor up against Southeast Michigan later Saturday
morning. System relative isentropic ascent is not the greatest, but
direct cva from PV anomaly lifting directly into the cwa and narrow
axis of deep midlevel moisture will bring increasing rain chances
for Southeast Michigan after 10 or 11Z Saturday. There is some lower
confidence on coverage given model depictions of a very narrow axis
of precipitation, however, the data suggests a relatively longer
duration of rain through early afternoon Saturday for those areas
directly impacted.

For DTW...There will be a tendency for the wind direction to veer
toward the north-northeast late this evening. The strengthening
gradient will support gusty NNE winds through daybreak Saturday.

.DTW THRESHOLD PROBABILITIES...

* High for cigs aob 5kft.

&&

.PREV DISCUSSION...
Issued at 245 PM EDT Fri Apr 19 2019

DISCUSSION...

Mainly dry conditions (outside of a little bit of drizzle) this
afternoon with low clouds holding on, along with brisk north-
northwest winds and temperatures in the the 40s.

Large upper level system over the Gulf Coast States this afternoon
with be tracking northeast, with max 6HR height fall center lifting
through Eastern Ohio tomorrow morning and through Western PA during
the afternoon. The surface low looks to be bottoming out this
evening (982-984 MB) close to the eastern Kentucky/West Virgina
border. The pressure falls over the Central Appalachians has helped
the winds go northwest over western Lake Erie, which is helping keep
water levels in manageable levels for the moment. Although, winds
should still come back around to the north-northeast and increase
overnight as the surface low (987 MB or less) reaches near
Pittsburgh PA, and will issue a lakeshore flood advisory
for Monroe county, with Luna Pier and points south seeing the
biggest impact due to the due to the northerly wind direction.
The Lakeshore flood advisory continues to look good for Saginaw Bay
and southern Lake Huron, as Essexville continues to reside above 50
inches above LWD.

Narrowing moisture/instability axis lifting into the eastern Great
lakes, arching back into the Central Great Lakes, with 12z NAM/GFS
indicating good 850-700 MB lift with the deformation axis lifting
from southeast/Monroe county (~12z) to northwest/Tri-Cities region
(~21z) during Saturday with 6 g/kg of Specific Humidity to work
with. Even so, local probabilistic guidance suggests QPF only around
half an inch for much of the CWA due to the progressive movement of
the forcing. This amount of QPF should not be much of a problem with
the extended mainly dry period this afternoon/evening helping.

The narrowing 850-700 MB Theta-E ridge will attempt to slide into
western Lower Michigan late in the day, or just continue to
wane/dissipate over southeast Michigan Saturday Evening/Night. If
low clouds clear out, fog could become an issue with calm/near calm
winds and saturated ground. However, it is looking more likely
there will be enough low level moisture (925-850 MB) trapped
underneath the mid level subsidence/inversion to hold low clouds in
through a good part of Sunday before mixing depths increase enough
and drier northwest winds kick up. Even when low clouds clear, warm
advection high clouds will then be on the increase as the upper
level ridge axis over Western Great Lakes slowly weakens and folds
over into southeast Michigan Sunday evening. Banking on late day
clearing on Sunday to get temps into the 60s as forecasted, but
confidence is average at best.

Going into next week, conditions will feature more normal
temperatures and a chance for rain mainly late Monday into Tuesday.
Temperatures on Monday are still looking to push to the 70 degree
mark despite cloud cover moving in from the approaching wave.  This
wave moves across the area later on Monday bringing chances for rain
through Tuesday before surface high pressure moves back in.  This
high will keep the area dry through the remainder of the extended
period.  Highs throughout the rest of the week will reside near the
60s for highs and in the 40s for overnight lows.

MARINE...

A compact low pressure system forecast to lift into the upper Ohio
Valley and eastern Great Lakes on Saturday will support increasing
north-northeast winds across the lakes tonight into Saturday.
Probabilities are high that wind gusts across Saginaw Bay and the
southern basin of Lake Huron will be around 30 knots. The strength of
the gradient will also support gusts of 25 to 30 knots across Lake
St Clair and western Lake Erie. This and the resulting waves will
sustain hazardous conditions to small boats. The departure and
subsequent weakening of the low will result in steadily decreasing
winds and waves across the lakes Saturday afternoon and evening. The
weak gradient and sfc winds will give way to light southeast winds
late Sunday into Monday.

HYDROLOGY...

As of this afternoon, 24-hour rainfall totals across Se Mi have
ranged from a third an inch around Midland to three quarters of an
inch across metro Detroit/Ann Arbor and points south. After a break
in the rainfall this afternoon and evening, another round of rain is
forecast to lift into the region from the east late tonight through
Saturday morning. The rain is forecast to dissipate over the area
Saturday afternoon. Additional rainfall totals late tonight/Saturday
are forecast to be around a half inch or less. Given the large break
in rainfall today, these forecast rainfall amounts do not pose any
flooding concerns.

Strengthening northeast winds tonight into Saturday morning will
create the risk for some erosion and minor flooding along the
lakeshores, mainly around Saginaw Bay, Lake Huron and Lake Erie
south of Monroe.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Lakeshore Flood Advisory until 5 PM EDT this afternoon for MIZ048-
     049-054-055-063.

     Lakeshore Flood Advisory until noon EDT today for MIZ083.

Lake Huron...Small Craft Advisory until 5 PM EDT this afternoon for LHZ421-422-
     441>443.

Lake St Clair...Small Craft Advisory until 10 AM EDT this morning for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 10 AM EDT this morning for LEZ444.

&&

$$

AVIATION.....JVC
DISCUSSION...SF/SP
MARINE.......SC
HYDROLOGY....SC


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