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Area forecast discussion...updated 
National Weather Service Twin Cities/Chanhassen Minnesota
706 PM CDT Friday Aug 29 2014

Short term...(this evening through saturday)
issued at 256 PM CDT Friday Aug 29 2014

Two areas of convection across the upper Midwest and Central
Plains will likely congeal into a line or broken line across
ec/SC Minnesota by late this afternoon/early evening. This is based on the
current surface trough across central Minnesota and the upper low across
western Iowa slowly moving east/NE across the upper Midwest/western
Great Lakes region by late tonight. The upper low across western
Iowa has a fairly strong jet streak moving northward which has
enhanced an area of upper level divergence in SW Minnesota since 1 PM
/hint increasing convection/. Higher instability across western
WI...as sunshine occurred...has also allowed for scattered thunderstorms and rain to
develop across this area. Weather/probability of precipitation reflect the current trend of the
hrrr/hopwrf as numerous rain showers/thunderstorms and rain are expected to develop across
ec Minnesota in the next few hours. As the upper low finally shears out and
move to the NE...the area of rain showers/thunderstorms and rain should move into wc WI by
middle/late evening. A period of heavy rainfall is likely in ec/SC Minnesota
during the late afternoon/early evening before tapering off after sunset.
Elsewhere...limited instability will likely hold off on widespread
shra/tsra...with only isolated coverage at best through sunset. Surface
winds behind the surface trough are fairly weak which may allow for
fog/low clouds to form overnight where the rainfall ended. Saturday
will be the driest for the weekend as weak high pressure settles
across the region.

Long term...(saturday night through thursday)
issued at 256 PM CDT Friday Aug 29 2014

Saturday night through Sunday night...surface high pressure with narrow
ridging aloft will cross over the region in tandem Sat night...
allowing for a fairly benign 12-hour period with mostly clear skies ahead
of what may be a fairly active late Sunday through Sunday night
period.

A very broad longwave trough over the northern Pacific will move
onshore the western Continental U.S. Sat and it is this trough that will work
with a developing area of low pressure off the northern rockies. A potent
axis off the longwave trough will swing over The Rockies sun while
the main trough centers itself over central Canada. This trough
will grab the developing low pressure center over the northern rockies and
shove it northeastward from northern Wyoming across the Dakotas into northern Minnesota by sun
evening...dragging a cold front into central-southern Minnesota. A warm front associated
with this system will rapidly shift northward during the day on
sun...allowing a strong surge of both warmer air /mid-80s for
highs/ and low-middle level moisture into the region...helping increases
precipitable waters /to over 1.25 inches/ and instability parameters /MUCAPES
over 2500 j/kg/. Even any ongoing morning convection will lift off
to the north...making the morning into early afternoon potentially devoid
of precipitation...setting the stage for later in the day. Strong height
falls combined with heightened deep layer shear will allow for
elevated convection to quickly become surface-based in the middle-to-late
afternoon hours. Best timing for the potential for severe weather looks to
be 21z-00z in western Minnesota...then transitioning into eastern Minnesota into western WI
00z-06z. The current thinking is several clusters of storms will
become quite organized... possibly even showing characteristics of
a mesoscale convective system or qlcs when late day and evening jetting increases. This event
looks to feature The Hazards of large hail and damaging
winds...not so much tornadic characteristics. The cold front looks to
clear Minnesota and much of western WI by daybreak Monday morning...bringing this
event to a close while fairly zonal flow sets up aloft.

Monday-Thursday...a weak quasi-stationary front will develop S of the
area by mid-week... giving more of a focus for organized
showers/thunderstorms Wednesday into Thursday...as opposed to Monday-Tuesday which will be
more of the isolated pop-up variety with little strength. Improved
coverage for storms is expected Wednesday-Thursday with the addition of the
front and several weak shortwave buckles within the prevailing
zonal flow...but mainly showers with possibly a few thunderstorms. Temperatures
cool down on the backside of the departing cold front Monday...with highs
back into the middle-70s before warming back into the lower 80s by
late week as warmer air surges north with the development of the
lingering surface boundary.

&&

Aviation...(for the 00z tafs through 00z Saturday evening)
issued at 705 PM CDT Friday Aug 29 2014

Most of the thunderstorm activity has shifted east into central
WI...but a few cells remain near eau. Otherwise...a band of light
rain from msp to rwf will slowly shift east this evening. Some
rain may fill in to the east as the upper low lifts northeast. Drier
middle level air will erode precipitation chances from the west
overnight...but ample low level moisture will bring the likelihood
of more widespread IFR/LIFR conditions after 08-09z. Gradual
improvement expected Saturday with VFR forecast by early to middle
afternoon.

Kmsp...light rain will continue for the next several hours before
ceilings drop back into IFR and/or LIFR levels overnight. Confidence
is high of this occurring...but confidence in timing is a bit
less.

/Outlook for kmsp/
sun...VFR with MVFR/thunderstorms and rain late. Winds south-southeast at 10-20 kts.
Monday...MVFR/tsra ending early. VFR by afternoon winds west 10-15kts.
Tuesday...VFR with MVFR and a slight chance thunderstorms and rain. Winds west-southwest 10 kts.

&&

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

$$

Short term...jlt
long term...jpc
aviation...borghoff

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