Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
352 am CDT Tuesday may 26 2015
Short term...(today and tonight)
issued at 329 am CDT Tuesday may 26 2015
Today and tonight...surface analysis shows a pair of well-defined low
pressure centers...one near kdlh and another near koma...linked by a
trailing cold front from the former to a leading warm front from the latter.
Meanwhile...the combination of the subtropical ridge centered over
Florida with a deep longwave trough axis entering the upper miss River Valley
remains. A cutoff low looks to develop within the trough over eastern South Dakota
and this feature will traverse eastward over southern Minnesota during the day today. In
concert with this scenario...the surface front will also slowly move eastward
across the area while the low pressure center near koma shifts northeastward along
the front. The deepening of the upper low combined with the arrival of
the surface feature will allow for an expansion of showers /and isolated
thunderstorms/ from around the Minnesota/Iowa border northeastward into western WI...possibly
giving a glancing blow to the Twin Cities metropolitan. Best shot of rain
will be mainly along and east of a line from Rice Lake-Cottage Grove-
Fairmont...and hrrr/hopwrf/sref indicates enough cape to potentially
see a few thunderstorms developing within the activity. As the front shifts
off to the east...so will the precipitation shield...so will look for precipitation
to diminish from west to east this evening into the early morning hours. Precipitation
is expected to be well off to the east come daybreak Wednesday morning.
As for temperatures...mild air in advance of the surface front will keep
temperatures in the 50s this morning but modest cold air advection with the advance of the
fnt will hold highs back in the lower 70s today. Only partial clearing
tonight along with winds backing to westerly will result in another mild
night with lows in the middle 50s.
Long term...(wednesday through monday)
issued at 329 am CDT Tuesday may 26 2015
By Wednesday morning skies will have mostly cleared as upper level
ridging builds into the area. The forecast highs remain on track
as a surge of warm air pushes in. Much of the latest guidance
agrees that widespread middle 80s are certainly plausible so made
little change to the forecast highs for tomorrow.
Thursday through Friday...we get on the back side of the upper
ridge by Thursday which means we'll see southwest flow and
increase in moisture and potential for showers and thunderstorms.
Temperatures will be warm again...slightly cooler than Wednesday. Slowed
probability of precipitation down slightly through Thursday afternoon but still have
likely probability of precipitation pushing in form the west ahead of an approaching
trough. Worked those likely probability of precipitation across the remainder of the area
Thursday night into Friday. A decent cold front will push through
from west to east from late Thursday night through Friday. Precipitation
chances go away once the front pushes through.
Friday night through Monday...by the start of the weekend we'll be
in a Post frontal northerly flow with a decent cool down expected
as a surface high from Canada pushes south into the upper Midwest.
Highs on Saturday will be comparable to Friday morning lows...so
its either 10 degrees above or below normal in this pattern. 850mb
temperatures may cool to the lower single digits and with potentially
mostly clear skies and light winds...could see some temperatures in the
30s by Sunday morning. There is quite a bit of disagreement
between the ec and GFS concerning the potential for precipitation in
southern Minnesota Sunday...so stuck with a blend for now and continued
slight chance probability of precipitation. We get back to a more southerly flow Monday
which will lead to a warming trend toward the middle of next week.
Aviation...(for the 06z tafs through 06z Tuesday night)
issued at 1229 am CDT Tuesday may 26 2015
Low stratus across central Minnesota will very slowly drift southeast
overnight...with a mix of IFR/MVFR ceilings. In western WI...fog will
likely impact the taf sites overnight. Keau has already send visible
fall below 2sm. MVFR ceilings are likely through the morning for most
sites...before ceilings raise above 3k feet. Skies begin to scatter
from west to east late tonight. For tomorrow...showers and
thunderstorms are most likely across western WI.
Kmsp...no change from main discussion. Expecting most showery
activity to stay east of msp for Tuesday.
/Outlook for kmsp/
Wednesday...VFR. Winds west 5-10 kts.
Thursday...VFR. Chance p.M. -Shra/-tsra. Winds southeast at 5-10 kts.
Friday...MVFR in shwrs/tsms. IFR possible. Winds SW 5-10 kts becoming
north 10-15 kts.