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Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota
329 am CDT sun Apr 20 2014

Short term...(today and tonight)
issued at 301 am CDT sun Apr 20 2014

Latest surface analysis shows a nice surface dewpoint gradient
extending from southwest Minnesota northeast into northwest
Wisconsin. Rap 925-700mb layer moisture convergence shows a decent
area of deep moisture convergence along this same general axis...
and we continue to see scattered rain showers developing along it. The rap
suggests it will remain fairly stationary through around 10z then
sink southeast and mainly just impact the far southeast/east portion
of the forecast area. The hrrr and hopwrf indicate a similar
evolution of things... with activity dropping a bit south after 10z
or so. However... the baroclinic zone doesn/T look to drop too much
farther south through tonight... so although we should see activity
get south of the Twin Cities metropolitan this morning... it doesn/T look
to completely exit the forecast area anytime soon. In fact... the
shortwave currently evident over the northwest Continental U.S. In water vapor
imagery will make its way east toward the area this evening. This
will mainly work to generate some precipitation with a surface wave to our
north along/north of the Canadian border tonight into Monday
morning. However... the southern extension of the upper wave looks
like it will help generate a wave along the stalled baroclinic zone
nearly the southern portion of the forecast area during the
overnight into early Monday morning. The GFS and European model (ecmwf) bring precipitation
farther north again later tonight into Monday as this occurs... and
it would seem to make sense given the additional forcing and area of
elevated instability prognosticated to move through the area along/ahead of
the upper wave. So... generally pushed probability of precipitation southward through the
day today... then lifted chances north again tonight before
gradually shifting them eastward late tonight as we finally see see
some surface ridging begin to move in from the west.

Long term...(monday through saturday)
issued at 301 am CDT sun Apr 20 2014

Longer term concerns include fire weather potential Monday
afternoon across the west. Then the development of the western
Continental U.S. Trough toward midweek with the thunder threat building east
into the area Wednesday into Thursday. Ultimate timing of the
trough over the area also remains a problem through the remainder
of the week.

The models may have slowed the progression of the front across the
region for Monday morning. Will leave a small chance over the
eastern County Warning Area through about midday Monday. Then cooler...drier air moves into
the area with increasing northwest winds. We should see a general
clearing sky with perhaps some cumulus development over the
Central Area into Monday afternoon as the cooler air moves in.
Northwest winds 20-25 miles per hour are expected to develop over the west
into the afternoon and relative humidity values will drop off to
25 to 30 percent over the southwest in the afternoon. Will have to
monitor this region during the day and see if dewpoints drop
further. Will continue to mention the drier humidity and winds in
the fire weather discussion.

Pleasant weather expected for Tuesday with lighter winds as the
high drops over the area. The western Continental U.S. Trough moves east with
increasing moisture and instability increasing especially Wednesday
night into Thursday over the area. Will likely see some initial warm air advection
showers move in Tuesday night. The low level jet increasing to the west over
the eastern Dakotas later Wednesday night and spills into far
western Minnesota late. Then this will translate east into Wednesday with
the continued chance of showers. Some isolated thunder will work
into western areas mainly during the day Wednesday. We did remove
the thunder threat farther to the east.

The trough and associated surface low develops to the northeast
Wednesday night into Friday. The longer term models remain in
disagreement on how fast the trough moves the the area. The GFS
remains the slowest and will likely trend that way for now. Will
continue thunder threat over the entire County Warning Area Wednesday night and
Thursday. Severe weather threat will be limited as it appears the
real warm sector may be have some difficulty penetrating the
cooler/cloudy area over much of Minnesota. It still appears it
will get cold enough for at least a rain/snow mix developing
Friday night into Saturday and again Saturday night into Sunday.

&&

Aviation...(for the 06z tafs through 06z Sunday night)
issued at 1212 am CDT sun Apr 20 2014

Primary aviation concerns are the chances for some rain showers over the
southeast half or so of the area overnight into the morning... along
with the potential for fog from the northern edge of that precipitation on
northward during the overnight hours into early this morning. A
frontal boundary is very slowly sinking southeast... with some
weak warm advection and moisture transport aloft helping to keep
scattered rain showers going near the boundary. The hrrr and hopwrf keep
some activity near kmsp for the next few hours... then drop it
southeast and out of all but perhaps Keau by morning. Ceilings
should remain VFR with any rain showers... but could see visibilities dip
into MVFR range for brief periods. North of the frontal boundary
and scattered rain showers we/re seeing fog develop in areas north of the
cloud cover... particularly where snow melted yesterday. Could
definitely see some issues with IFR and perhaps some LIFR at kstc
and krnh through 13z or so this morning. Otherwise... the next
item of interest will be a weak shortwave that is expected to move
through the region later tonight... potentially rejuvenating the
rain showers activity across the area since the baroclinic zone will still
be loitering in the vicinity. It appears to be an issue mainly
after 06z... so at this point the only taf where any mention is
needed should be kmsp... so included a vcsh there after 07z.

Kmsp...primary uncertainties are with when we/ll see the current
rain showers activity finally drop south of the area. Have reasonable
confidence in the forecast timing... but it/S possible it could be
1-2 hours slower. In addition... included some MVFR fog before
daybreak as the thicker cloud cover departs and we potentially see
a bit of radiation fog development. Confidence in that possibility
is also fairly low... and it could easily not occur or be a bit
worse should clouds depart more quickly than expected.

/Outlook for kmsp/
Monday...MVFR ceilings and visibilities possible early with a
chance of rain showers. Northwest wind 10 to 20 knots.
Monday night...VFR. Northwest wind 10 to 15 knots.
Tuesday...VFR. Northwest wind less than 10 knots becoming variable
less than 5 knots.
Tuesday night...VFR. Southeast wind 5 to 10 knots.
Wednesday through Thursday...MVFR ceilings and visibilities
expected with rain likely. IFR conditions possible along with a
chance of thunderstorms. Southeast wind 10 to 20 knots becoming
southwest.



&&

Mpx watches/warnings/advisories...
Minnesota...none.
WI...none.
&&

$$

Short term...trh
long term...dwe
aviation...