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Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota
428 am CDT Thursday Sep 18 2014

Short term...(today and tonight)
issued at 405 am CDT Thursday Sep 18 2014

A cooler air mass moved SW across Minnesota overnight. The leading edge
of this cooler air mass had some lower clouds...along with gusty
NE winds. Although return flow will commence later today...some
residual low clouds/fog may develop and persist across portions of
Minnesota/WI before noon. Not too many changes overnight as the main forcing
remains north of mpx County Warning Area through 12z Friday. Moisture levels due
increase today/tonight in response to increasing southeast/S winds. The
best chance of rain showers/thunderstorms and rain will occur in central Minnesota...with the bulk of
the heavier activity in northern Minnesota before daybreak Friday. Even
some of the cams reflectivity pattern holds the bulk of the
convection north of mpx County Warning Area. Temperatures may be a few degrees cooler
than on Wednesday...but still rising into the 70s in Minnesota...with
lower to middle 60s in wc WI.

Long term...(friday through wednesday)
issued at 405 am CDT Thursday Sep 18 2014

Friday through Saturday...the main focus for the extended portion
of the forecast remains in this 36-hour period. An approaching upper
level ridge from the northern plains will flatten as it enters the upper
miss River Valley region. Right on the heels of this dissipating
ridge is a digging shortwave trough. This trough will aid in the
lifting of a surface warm front over the Dakotas and MN/WI...while a pair
of low pressure centers /one over southern Manitoba province and another
coming off the Lee of The Rockies/ shift eastward in tandem. A cold front
trailing southwestward from the northern low will slowly approach from the west
during the day on Friday and gradually cross the region Friday night into
Sat morning. A deep plume of moisture from the Gomex on the backside
of the departing high will thrust higher dewpoint air into the
region...helping build instability in advance of the cold front for Friday
afternoon and evening. While some scattered showers and possibly a few thunderstorms
are possible during the day on Friday with the warm front...the bulk of the
precipitation activity will occur Friday night in the warm sector of this
system. Capping aloft will dissipate by the evening hours but there may
be some inversion at/near the surface which may inhibit more
widespread convection. Nevertheless...MUCAPES approach the
1500-2000 j/kg range...0-6km bulk shear reach 40-45 knots and midlvl
lapse rates become decent enough for strong storm strength
/approximately 7.0-8.0 c/km/. This will allow for not only decent
coverage of thunderstorms...especially in eastern Minnesota into western WI...but also for the
small possibility that should storms grow deep enough with the
approaching upper level shortwave trough...some storms could be strong
to severe with large hail or damaging winds. Storm Prediction Center swody2 maintains
a 5 percent severe thunderstorm risk over central and southern portions of the
County warning forecast area for Friday night which is certainly reasonable. As the cold front
pushes through the region Friday night into Sat morning...coverage of
precipitation will diminish as precipitation ends from west to east. Only some
lingering showers are expected for the first half of Saturday. As
for temperatures...a noticeable warming trend will take place with
the lifting of the warm front across the area Friday and ahead of cold air advection that
is not expected to truly kick in until after maximum temperatures have been
reached on Saturday. Highs will hit the middle-upper 70s both days
while dewpoints climb to the climb to the low-middle 60s...producing
heat index values into the low-middle 80s.

Sunday through Wednesday...the warmup and precipitation activity featured
in the Friday-Sat period will not be present for the remainder of the
long-term forecast period as Canadian high pressure follows the cold front Sat
night. This cooler and drier high pressure airmass will then remain
over the area through the middle of next week...keeping the area
devoid of precipitation and temperatures close to normal values.
Highs will struggle to hit the 70-degree mark...likely remaining
in the middle-upper 60s...with lows in the 40s to around 50.

&&

Aviation...(for the 12z tafs through 12z Friday morning)
issued at 415 am CDT Thursday Sep 18 2014

LIFR/IFR ceilings/visibilities at kaxn will likely persist for a few hours
during the morning. Timing is the main concern...but
14-16z...LIFR/IFR ceilings/visibilities should quickly lift. Krwf may see an
hour or two of LIFR ceilings...but again this should lift quickly after
sunrise. Kstc/krhn/Keau will remain the most problematic aviation
sites this morning due to deeper influx of moisture across WI
moving west/northwest across this region. Kept conds IFR/MVFR through
15-17z...before diurnal mixing should allow for ceilings to lift to
VFR during the late morning. Winds will start from the east/NE around
5-10 kts...veer to the southeast and increase during the afternoon. The
pressure gradient remains tight overnight...so kept winds in the
10-15 knots range...even some gusty winds above 20 kts are likely.

Kmsp...

IFR ceilings across WI may affect the air terminal during the morning.
Confidence is low on IFR ceilings...but higher for MVFR ceilings after
13-14z. If these ceilings develop...it should quickly lift to VFR by
the late morning. Winds will start from the NE around 8 kts...veer
to the east this morning...then more southeast and increase above 12 kts
during the aftn/evening. Some gusts will also accompany the higher
wind spds tonight. Any rain showers/thunderstorms and rain activity should be north of the
Airport...with low confidence on vcsh/thunderstorms in the vicinity after 12z/19.

/Outlook for kmsp/

Friday afternoon...VFR. Chance rain showers/thunderstorms and rain before 9 PM. More numerous after 9 PM with
MVFR/IFR cigs/vsbys. Winds S-SW 15-25 knots.
Sat...VFR. Morning -shra possibly MVFR ceilings. Winds northwest 10-15 knots.
Sun...VFR. Winds northwest 10-15 kts.

&&

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

&&

$$

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

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