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Area forecast discussion 
National Weather Service Detroit/Pontiac Michigan
1155 PM EST sun Dec 28 2014



Aviation...

A secondary cold front is slowly bringing low clouds back to the taf
sites from north to south early this morning. These clouds are
already overhead at fnt and mbs and should make it over the metropolitan
airports by 08z. The initial surge is MVFR...with ceilings rising to
VFR a few hours after they are overhead. These low clouds should
last through the afternoon hours over the taf sites with some
possible relief Monday evening.

For dtw...a secondary cold front is expected to bring ceilings down to
around 2500 feet by 08z...slowly lifting to around 3500 feet by
09z...lasting through the afternoon hours. Surface winds will remain
relatively light...veering light northwest with time.

//Dtw threshold probabilities...

* high that ceilings will fall below 5000 feet by 08z...lasting through
Monday afternoon.

&&

Previous discussion...issued 345 PM EST sun Dec 28 2014

Short term...tonight

Low level cold advection in northerly flow regime with increasing
confluence aloft will allow surface ridging to aggressively build
across the Great Lakes region tonight. A secondary cold front...now
in place over portions of northern Wisconsin and the up...will enter
into the northern basin of Lake Huron tonight and become hung up at
least partially due to lake aggregate effects. The lower
tropopsheric frontal structure will push slowly southward toward the
County Warning Area...but is expected to remain north of the County Warning Area through 12z Monday.
Southeastern Michigan will remain under the upper level jet axis
overnight which maintains the potential for high cloud. Satellite
high cloud now in place over portions of sodak and so min is
forecasted to spill eastward with time sliding over the area towards
daybreak. Increased clouds late...but should not have a huge
influence on lows...with temperatures expected to fall into the middle
20s by midnight.

Long term... Monday through Sunday

An Arctic cold front moving southward through the northern Great
Lakes and plains today will settle into lower Michigan during
Monday. Upstream observations indicate just some flurries associated
with a lean supply of Pacific moisture in the middle levels except for
in the Lee of Lake Superior. A modest lake effect response is in
progress there and mostly describes the character of the front as
needing that boost from the lakes to produce any meaningful snow. A
strong northwest component in the low level wind field is shown with
good agreement in model data by the time the front reaches Southeast
Michigan Monday morning. A low end chance pop for snow showers will
cover frontal convergence maintaining some integrity while coming
Down Lake Huron into The Thumb. After that...the surface front will
quickly wash out into broad northwest flow as the water generates
weak/thermally induced pressure troughing over Middle Lake by
afternoon. Confluent flow aloft and increasing influence of the left
entrance region of upper jet in southern stream will present
increasingly unfavorable large scale support which will squash an
infusion of new Pacific moisture in the middle levels. Plan to then
maintain dry conditions or no more than a snow flurry during the
rest of the day through Monday night over inland areas of Southeast
Michigan.

Persistent northwest low level flow will maintain cold but dry
conditions through the middle week period. The latest model output
remains locked in on digging the Pacific coast energy in the
southern stream into a closed upper low over Southern California by
Wednesday. The northern stream trough axis that is linked to the
closed low will then break away to the east and reinforce cold air
over the Great Lakes. This will set up a cold entrance for the New
Year with solid looking guidance offering maximum temperatures barely in the
20s Wednesday.

The latest global model solutions show impressive adjustments on the
large scale pattern during the second half of the week and
especially next weekend. European model (ecmwf) dprog/dt at 00z Sunday is about as
dramatic as it gets as it keeps the upper low closed as it drifts
into Texas by Saturday. The other models all offer faster absorption
of the low into the northern stream as extra height falls over
western Canada act as a kicker during the end of the week. It is
encouraging to see the parallel GFS show meaningful spread with a
considerably slower solution than the operational GFS...but the
forecast spread among the individual solutions remains immense. A
substantial rain/snow event remains in play for Southeast Michigan by
Saturday as depicted by the operational GFS...but so does dry and
continued cool conditions depicted by the European model (ecmwf). The cut-off
character of the southern stream system during middle week continues to
favor slower and/or farther east solutions...but taking the dramatic
European model (ecmwf) adjustment with some caution.

Marine...

Modest west to northwest wind will persist tonight and be reinforced
by the passage of an Arctic front during Monday. Much colder air
will funnel over Lake Huron and lower Michigan with this front but
wind speed will remain at moderate levels through Tuesday. Some
increase in winds is expected by Wednesday and Thursday presenting a
low potential for west or southwest gales over central portions of
Lake Huron during this time.

&&

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

$$

Aviation.....Kurimski
short term...cumulonimbus
long term....bt
marine.......bt



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