Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 282026

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
326 PM CDT WED SEP 28 2016

.SHORT TERM...(This evening through Thursday)
Issued at 315 PM CDT Wed Sep 28 2016

Water vapor imagery indicates the center of the upper low has
progresses southward today, with the main circulation over northern
Indiana.  This low is the culprit for the widespread cloud cover
across the forecast area today.  The stratus is beginning to erode
across far western MN at this time, but one of the main concerns
this forecast period is if we need to slow down the departure of the
stratus.  Some of the available guidance wanted to keep the clouds
in place through the night, but the majority was still optimistic in
scouring it out.  Given the cool temps, shrinking daylight hours,
and the upper low nearby, I don`t see the clouds truly clearing
until the ridge axis arrives.  So, went ahead and increased cloud
cover through the night and much of tomorrow morning.  But, maybe
not enough.  A feasible scenario is to continue to see erosion in
western MN through this afternoon, but what can happen this time of
year is for that erosion to halt once its dark out, with the clouds
having no reason to move.  This will be monitored this evening and
increased further if the erosion of the western edge does stop. What
is holding us back from going with an overcast forecast overnight is
the dry air pushing in from the west and the fact that the upper low
is going to continue distancing itself from here, reaching Kentucky
by tomorrow morning.

For tonight, should see temperatures into the low and mid 40s in
western MN where confidence is better in seeing partly cloudy to
clear skies.  Farther east where clouds may linger, kept temps in
the upper 40s or lower 50s. Would not be surprised to see fog
develop in eastern MN/western WI if the clouds scatter out, but only
if that happens.  On Thursday the upper ridge continues pushing in
so while we may have cloud cover lingering through the morning,
should see that scatter out as dry air wins out.  Highs will
generally be in the mid 60s and at the surface the pressure gradient
will have weakened which will provide a reprieve from the recent
windy conditions.  No precipitation is expected.

.LONG TERM...(Thursday night through Wednesday)
Issued at 315 PM CDT Wed Sep 28 2016

The longer term concern is the movement of closed upper
circulation over the Great Lakes and Ohio River valley early
on...then trending the continuation of amplified pattern toward

The long term deterministic models continue to slow movement of
the upper circulation over the Great Lakes region through Sunday.
The low rotates northwest and will likely spread more clouds over
the area Friday night through Saturday night. A small chance of
showers will also move into west central Wisconsin Saturday as the
deepest moisture moves across that region. Further west...a
surface ridge remains quasi stationary through the weekend with
light winds expected.

This upper low will be finally be jettisoned to the east early
next week as another strong trough moves ashore over the western
CONUS. This energy shifts east...and may be slowed by a
combination of amplified ridging to the east and the influence of
the next tropical system/Matthew moving through the Caribbean. We
will trend slower with increasing pops again to mainly the western
CONUS Monday night and then east across the cwa through Tuesday
night. There is some thunder threat as well...with the GFS faster
with the initial short wave and developing at least a weak line of
convection Tuesday night and more so Wednesday for the slower
ECMWF. Depending how this energy lifts out of the western CONUS
trough...some strong storms could occur Tuesday least
for a portion of the cwa. We will have to continue to monitor long
term trends for this possibility. Temperatures should range close
to normal early...with warmer than normal conditions ahead of the
next trough into midweek.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1254 PM CDT Wed Sep 28 2016

Stratus shield blanketed across the Upper Midwest this afternoon
has gradually lifted with pockets of VFR mixed in with MVFR cigs.
The ceiling should continue to slowly lift with all sites going
VFR this afternoon. The big concern with this forecast is for
tonight and tomorrow. Continue to advertise clearing of skies but
there is bust potential given the upper ridge axis takes until
tomorrow to reach our area. If the clouds are able to scatter out,
we could see fog form overnight which has been advertised in a few
of the sites.

KMSP...concern that the SKC forecast at 02Z could be really early.
A few models indicate the clouds could stick around and that MSP
might see MVFR ceilings form early tomorrow morning.

Thu...VFR. Wind NE at 5-10kt
Fri...VFR. Wind ENE at 05kt
Sat...VFR. Wind ENE at 05kt.


.MPX Watches/Warnings/Advisories...


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