Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 020457
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1157 PM EST Mon Mar 1 2021

.AVIATION...

High pressure continues making inroads across southern lower
Michigan late tonight with abundant dry air keeping VFR conditions
favored through the forecast. The center of the high slides along
the MI/IN/OH border region early in the period with surface winds
then organizing out of the SSW during the morning hours. The next
low pressure system quickly moves into the northern Great Lakes today
bringing an increase in SW wind along with thickening mid level
clouds mainly to the north. Wind gusts ramp up to the 20 to 25 kt
range during the late afternoon then taper off during the evening
with the loss of daytime mixing. The low tracks off to the east late
in the period with dry/VFR conditions prevailing.

.DTW THRESHOLD PROBABILITIES...

* None.

&&

.PREV DISCUSSION...
Issued at 403 PM EST Mon Mar 1 2021

DISCUSSION...

Closed low up to 400 mb migrates eastward this evening with
departing confluence over the Ohio Valley. A surface cold/arctic
front has already cleared the CWA with surface obs denoting slightly
veered winds (290-320 degrees) and dewpoints trending toward single
digit values. Morning WSR-88D Z returns illustrated the efficacy of
subsaturated air in the lowest kilometer AGL. Just a few midday
flakes reported from passing stratocumulus sustained along a layer
of orthogonal system-relative saturated isentropic ascent (850-600
mb) in phase with a filament of CVA. Most of the broken line has now
crossed south of the MI/OH border at press time, and will therefore
advertise dry PoPs after 21Z. Additionally, expect winds/gusts to
diminish into the overnight hours as the deep mixed-layer thins
toward the surface inhibiting downward momentum transfer coincident
with weakening sub-H8 flow behind the wave.

Robust differential cold advection will cease after midnight as the
inflection point within the northern stream jet tracks into the
northern Great Lakes. Expect chilly temperatures overnight with lows
in the low-mid teens. Did bump mins up a couple degrees this cycle
given sky trends holding on to some BL and marginal elevated
moisture causing periodic cloud to help preserve some outgoing
longwave radiation. The sheared inbound ridge axis with warmer air
begins to moderate the low-mid portion of column early Tuesday
morning as H8 temps rebound into to positive territory over the
course of the day. Zonal shift in the H8-H7 layer with modest quasi-
geostrophic speeds could mix down peak gusts in the 25-30 mph range
late Tuesday (19-23Z) within prevailing southwesterly gradient. Max
gusts will be closer to 35 mph for locations IVOF the Tri-
Cities/Thumb as the amplified LLJ carves through central Lower
Michigan. With the exception of some stratocumulus, mid-level
anticyclone ensures a dry forecast on Tuesday while central surface
high pressure brushes south of the region.

Went against blended guidance (auto-populated 0-2 PoPs) for
Wednesday evening and night. Although moisture quality is sub-par,
still enough associated lift with the cold FROPA to support perhaps
Slight Chance for precip over the southern half of the FA.
Borderline snow/rain along the frontal slope based on forecast
soundings and the height/temperature level of inversion. Current
solutions appear lacking in available IN given the extensive mid-
level (875-575 mb) dryness. For what it`s worth, 01.12Z GFS is much
warmer than the equivalent NAM12 (recent cold bias), thus recommend
rain as the more likely outcome. A liquid p-type also makes more
sense in the context of diurnal heating coupled with resident low-
level warm sector airmass traced back to Gulf origin. Afterwards,
longwave troughing toward the Canadian Maritimes yields to a folding
central CONUS ridge late this weekend guiding temperatures from near
normal to well above normal by Sunday and Monday with mainly dry
conditions.

MARINE...

Ongoing northwest gales and freezing spray over Lake Huron will
continue into the evening before tapering off tonight as cold
advection gradually wanes. Wave heights increase through the
afternoon for the Lake Huron nearshore zones - peaking around 5 to 7
ft this evening - and a Small Craft Advisory remains in effect
through late tonight. A brief lull in wind strength occurs Tuesday
morning as high pressure shifts across the southern Great Lakes.
However, another low pressure system will be quick to drop into the
northern lakes and the resultant gradient will bring an uptick in
southwest winds across central Lake Huron on Tuesday. Another period
of gales is becoming increasingly likely for during the afternoon
and evening hours. Will allow the current Gale Warning to end later
this evening before issuing the next round. The associated cold
front moves through by Wednesday morning and will be much weaker
than the Sunday evening and Monday cold fronts. It will open the
door for an extended period of NW to N winds for the late week that
look to remain below headline criteria.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...NONE.

Lake Huron...Gale Warning from noon to 10 PM EST Tuesday for LHZ362-363-462.

     Small Craft Advisory until 10 PM EST Tuesday for LHZ421-441.

     Small Craft Advisory until 4 AM EST Tuesday for LHZ442-443.

Lake St Clair...NONE.

Michigan waters of Lake Erie...NONE.

&&

$$

AVIATION.....TF
DISCUSSION...KK
MARINE.......TF


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