Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion...updated 
National Weather Service Twin Cities/Chanhassen Minnesota
708 PM CDT Wednesday Oct 1 2014

Short term...(this evening through thursday)
issued at 316 PM CDT Wednesday Oct 1 2014

Afternoon analysis shows a stacked low over Manitoba...with the
associated boundary straddling the Minnesota/Dakotas border. The first
related wave of lift generated a healthy area of showers that will
continue to lift from east central Minnesota and west central WI toward
Lake Superior. In its wake...residual low level moisture and light
winds will contribute to pesky stratus and fog development tonight
into Thursday. Will need to watch west central Wisconsin where
conditions could lead to dense fog overnight...particularly near Eau

On Thursday...the next wave ejects northeast across the area from
the southern stream system. Expect another round of rain with a few
thunderstorms to Blossom over south/east central Minnesota and west central
WI Thursday afternoon. The primary uncertainty is how far west the
precipitation shield will extend. Have leaned toward the NAM/European model (ecmwf)
which restrict the categorical probability of precipitation east of a Redwood Falls to St
cloud Minnesota line. Have included 70-80 probability of precipitation along and east of the
Interstate 35 corridor for Thursday afternoon.

Temperatures tonight will hang in the upper 40s to middle 50s under the
extensive cloud cover...with low/middle 60s anticipated for Thursday.

Long term...(thursday night through wednesday)
issued at 316 PM CDT Wednesday Oct 1 2014

Thursday night through Friday night...the long term forecast picks up
during quite an active period of weather. An impressive fall low
pressure system will be coming together across the Midwest by
Thursday evening...and will spread moderate to heavy rain at times
into southeastern Minnesota through western Wisconsin. At this upper level trough that is positioned over The Four
Corners region today...will lift northeast as it begins to phase
with a deeply amplified northern trough dropping southeast from
Alberta through Saskatchewan. Strong frontogenesis...accompanied by
decent differential divergence and strong isentropic lift will be
focused from a line near Fairmont...through the east metropolitan toward
Taylors Falls and areas to the east. The surface low will advance
northeast from Missouri to near Green Bay by midnight Thursday
night...and will rapidly deepen overnight through much of Friday as
the northern and southern troughs phase together. For much of
central and especially western Minnesota...Friday will be mostly
dry. However...the deepening surface low will create very windy
conditions as a 1030mb surface high move in to Montana...meaning
quite a tight pressure gradient is expected across the upper Midwest
through the day. The center of the upper trough will be overhead by
middle day...and strong cold air advection will hold daytime
temperatures about 20 degrees below seasonal normals. Cold air
advection looks stronger at this point with 850h temperatures of -4 to cooled high temperatures Friday by about two to three degrees
everywhere...meaning most will see highs in the 40s...with wind
chill values lower than that. On Friday night...models indicate an
area of decent Theta-E advection moving through on the backside of
the system which may produce light precipitation across the eastern half of
the County Warning Area. Temperatures look to be cold enough for mixing in some
snowflakes overnight...especially across western Wisconsin...but at
this time no accumulation is expected.

Saturday through Monday...during this period...the aforementioned
fall system will advance north toward Hudson Bay and continue
deepening initially. Mainly dry conditions are in the forecast for
our area. The upper trough will keep the strong northwest wind
flowing over our area during this time...meaning quite a cold
weekend is in store. Early Saturday morning...temperatures in the
30s will be common...with areas in the northwest potentially
dropping below freezing. From Sunday through Monday...the strong
system will retrograde to just southwest of the Hudson Bay and
become vertically stacked.

Monday night through Wednesday...the weakening system will begin
pushing east and 850h temperatures will be on the rise. Temperatures are
expected to return to the 60s for highs on Tuesday. Disagreement
remains between the GFS/ec about the upper pattern toward the middle
and end of next week...which will dictate temperatures across the


Aviation...(for the 00z tafs through 00z Thursday evening)
issued at 708 PM CDT Wednesday Oct 1 2014

IFR or lower conditions are in place at taf issuance time over
most of eastern Minnesota and western WI as stratus and visibilities lower.
However...VFR conditions are in place from just west of St cloud
to just west of Mankato. Not anticipating this clearing to make
much or any progress eastward tonight with conditions remaining
steady or slowly deteriorating through the overnight. A slow
improvement expected Thursday ahead of more rain to move across
eastern Minnesota and western WI late in the period.

Kmsp...IFR or LIFR conditions through middle/late morning with MVFR
returning late in the period.

/Outlook for kmsp/
Friday...mainly MVFR with chance -shra. Winds west-northwest 20g30 kts.
Sat...VFR. Winds northwest 10-15 kts.
Sun...VFR. Winds northwest 10 kts.


Mpx watches/warnings/advisories...


long term...speed

National Weather Service Glossary of Abbreviations