Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus63 kdtx 270450 
afddtx

Area forecast discussion
National Weather Service Detroit/Pontiac Michigan
1150 PM EST sun Feb 26 2017



Aviation...

Southwest winds 10 to 12 knots will ease further overnight as
surface ridge builds across area. Winds will then remain under 10
knots Monday as they back to south and then southeast by evening.
With northern/southern streams currently split, concentration of
clouds will be north/south of area with just sct-bkn 5-10kft deck in
between. This will change somewhat Monday afternoon/evening as the
northern edge of southern shortwave traversing the Ohio Valley leads
to increased moisture and possibly a more persist bkn-ovc deck in
the 4-5kft area.

For dtw...south-southwest winds of 10 to 12 knots will decrease overnight and
remain light Monday, backing to the S and then southeast. Scattered VFR
clouds will be the rule into Monday afternoon with an increasing
chance of lower VFR bkn cigs on the order of 4-5kft after ~22z.

//Dtw threshold probabilities...

* low in ceilings aob 5000 feet after 22z Monday.

&&

Previous discussion...
issued at 342 PM EST sun Feb 26 2017

Discussion...

Upper wave will continue working across the northern Great Lakes
this evening, pushing surface low pressure eastward from Ontario
into Quebec tonight. Weak ascent at the leading edge of warm air and
Theta-E advection has allowed some virga to show up on radar over
the southern portion of Michigan. Cold front is meanwhile settling
into northern and central Michigan, with stronger forcing allowing a
snow showers to reach the ground there. These showers may brush the
Saginaw Valley or far northern thumb through mid-evening, but will
keep pops low due to very dry air observed in the low levels. Wind
gusts are expected to pick up for several hours this evening as we
reach peak heating and as low-level jet punches up into Southeast
Michigan. Steep low-level lapse rates may allow gusts near 40 mph to
reach the surface, particularly north of I-69, for several hours
between now and 800 PM before diurnal cooling allows surface-based
inversions to begin forming and gusts diminish.

The front will lose upper support and wash out over central Michigan
tonight and early Monday. Main impact from this boundary will be an
increase in clouds late tonight and Monday as it not only pushes
moisture southward, but also interacts with moisture streaming
northward between low pressure over the Southern Plains and a strong
dome of high pressure off the mid-Atlantic coast. Southerly flow
will boost temperatures into the mid and upper 40s tomorrow. Winds
will also be much lighter, cutting wind chill factor and making for
a pretty nice late winter day.

Upper trough off the Pacific northwest will swing into the nation's
mid-section Tuesday into Tuesday night, pushing an area of surface
low pressure up across the Great Lakes. As typical this many days in
advance, there are still model variations with the center of the low
track that leads to uncertainty with onset time and location of
precipitation. Despite other differences, models remain in line with
the idea of surface temperatures being warm enough for all rain late
Monday night through Tuesday night. Theta-E advection and
instability will ramp up late Tuesday and Tuesday night as 60 knot
low-level jet noses up into lower Michigan. This is when the best
chance for rain will be, with perhaps a few thunderstorms occuring
as well. The surge of warm air will also send temperatures back to
well above normal, in the 50s for most locations on Tuesday.

Surface low pressure east of Lake Huron will bring the continued
chance for precipitation throughout Wednesday, with pops diminishing
into the evening and overnight hours as the dry slot edges its way
into the Great Lakes region. Both GFS and Gem models show a robust
swath of drier air enter behind the low, while the NAM and European model (ecmwf)
models exhibit a second, disjointed surface low pushing through
southern Michigan throughout Wednesday morning and afternoon,
allowing precipitation to fall throughout the day. Additional
convergence between model runs will be needed in order to increase
confidence in both timing and pops. In any case, model runs do
converge on colder air entering the region behind the low. 850 mb
temperatures averaging 5-7 c on 12z Wednesday will quickly drop
below freezing by 21z weds. Surface temperatures will peak in the
upper 40s to lower 50s throughout the afternoon, dropping to
freezing/below freezing by the evening and overnight hours. As a
result, an all rain solution is forecasted for morning and early
part of the day on Wednesday, with a swift transition to a wintry
mix to snow solution by the evening from north to south. Otherwise,
a weak surface low will bring light snow chances Thursday into
Friday.

Well above normal temperatures are still on track for Wednesday as
warmer air ahead of the surface low allows temperatures to peak in
the upper 40s to lower 50s. Wednesday's cold front will return
temperatures into the 30s by both Thursday and Friday, with warmer
air once again expected to return for the weekend, bringing a second
chance to see another round of 40s/50s.

Marine...

A Gale Warning remains in effect today through this evening for
Saginaw Bay and Central Lake Huron with small craft advisories in
effect for the remaining marine areas. A cold front will settle over
lower Michigan and Central Lake Huron tonight and dissipate in favor
of high pressure by Monday morning. Favorable marine conditions in
the form of light south wind and milder air will then continue
through Tuesday. The next low pressure system is projected to arrive
Wednesday on a track through the central Great Lakes followed by
colder air on moderate northerly wind for the end of the week.

&&

DTX watches/warnings/advisories...
Michigan...none.
Lake Huron...none.
Lake St Clair...none.
Michigan waters of Lake Erie...none.
&&

$$

Aviation.....Dg
discussion...hlo/am

National Weather Service Glossary of Abbreviations