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Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
526 am CDT Sat Apr 19 2014
Short term...(today and tonight)
issued at 340 am CDT Sat Apr 19 2014
Short term concerns are shower/thunder threat today into tonight and
strong winds over the northwest County Warning Area early this morning.
Latest radar showing some weak returns moving into the northwest
corner of the County Warning Area this morning. Movement is east northeast around
50 kts. This does extend back to the southwest into Easter South
Dakota. Pressure falls remain over the northwest corner of the
state...and strong pressure gradient remains strong over the area.
This will will continue the strong winds into the area into the
morning hours. Will also likely see some gusty winds associated with
any heavier showers into the early morning as well...with strong low level jet
arcing to the northeast over the area and steep middle level lapse
rates. Isolated thunder still possible along the northern County Warning Area as the
trough approaches. We do expect the wind to gradually diminish as
the surface low moves northeast and weakens further and the surface
front moves into western Minnesota. The best forcing remains over the
northern portion of the state through the morning. Instability is
meager with the system. Best lifted indice's are fairly meager and the middle
level lapse rates begin to decrease into the afternoon...as the main
upper trough lifts northeast over the northeast corner of Minnesota. Still
will likely have enough convergence along the front to generate at
least some scattered type showers. Will retain the isolated thunder
mention as well...along the front into the evening. Afternoon
temperatures are expected to range close to 70 in the far south with
60s common in the snow free areas.
The front sags southeast over the area overnight and stall over far
southern Minnesota. Clouds should limit significant cooling to the
south...but clearing to the northwest will yield temperatures back
into the 30s overnight.
Long term...(sunday through friday)
issued at 340 am CDT Sat Apr 19 2014
The front will remain nearly stationary across southern Minnesota
Sunday. This will keep the shower/storm chances going across far
southern Minnesota and portions of western WI...but there are some uncertainties
regarding how far north this activity will develop. NAM/GFS are
much drier and further south while the Gem and European model (ecmwf) are further
north and seem to phase a bit with the feature approaching from
the plains. Did not modify probability of precipitation a whole lot from the previous
forecast to maintain some continuity...but probability of precipitation may need to be
expanded a bit if the NAM/GFS trend toward the Gem/ECMWF.
Meanwhile...drier air will encompass areas well north of the
front. Dew points may end up being a bit drier than currently
forecast...but light winds throughout the boundary layer may not
completely mix out the moisture at the surface as forecast
soundings indicate. Abundant sunshine should allow for steep low
level lapse rates...easily tapping into the warm air aloft and
making for a rather mild day with highs in the upper 60s to lower
Weak low pressure will track from North Dakota across northern Minnesota and
the northern Great Lakes Monday. Thermal ridging will be tamped
down late with the front and the surface high pressure building
south into the plains. Should still be enough time and available
sunshine to bring highs back into the 60s.
The surface high pushing across Minnesota will become elongated...
stretching from the Mississippi and Ohio valleys northwest into
northern Canada next week. As low pressure becomes organized over
the High Plains and northern rockies in response to a deepening
trough down the West Coast...a cool east/southeasterly boundary
layer flow will strengthen across the Midwest. Robust warm sector
across the plains and strong southwest middle level winds will spread
the eml northeastward into Minnesota/WI midweek. Low level warm air advection/moisture
advection on a potent low level jet and decent isentropic upglide
will be sufficient to generate a band of showers and thunderstorms
north of the warm front late Wednesday and Wednesday night.
The evolution of the system is less certain Thursday and Friday.
The European model (ecmwf) becomes negatively tilted and eventually occludes the
system over the County Warning Area with widespread showers continuing for the
remainder of the week. The Gem is further north and neutrally
tilted with the warm sector pushing north into Minnesota. The GFS is even
further north...but is quite fast with the cold front and dry
slots the County Warning Area Thursday with backside showers reaching the area
Friday. Given all of this...maintained chance probability of precipitation for late in the
week but most signs point to an unsettled period.
Aviation...(for the 12z tafs through 12z Sunday morning)
issued at 451 am CDT Sat Apr 19 2014
Areas of rain showers lifting northeast across the northern areas this
morning. Expect that to remain north...affecting kaxn/kstc. Then
front sags southeast over the area into the afternoon/evening.
Forcing remains weak...but scattered rain showers still possible with the
boundary into the evening. Any thunder threat should remain isolated
through the period. Expect ceilings to remain VFR with the
activity. Otherwise threat will end with frontal passage. Strong southeast
to south winds through the morning east and south...diminishing
first to the west...ahead of the boundary. Winds becoming more
southwest to wet with frontal passage...and eventually light north overnight.
still think most of the morning shower activity will remain to
the north of the Airport. Will continue the trend of best shot at
rain showers in the 19z/23z period. Expect VFR conditions through the
period. Strong southeast to south winds ahead of front will
diminish as front approaches late in the afternoon.
/Outlook for kmsp/
Sun afternoon/night...VFR. Winds north-northeast 5 kts becoming variable.
Monday...VFR. Winds northwest 10-15 kts.
Tuesday...VFR. Winds north 5 to 10 kts.