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Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota
1122 PM CDT Thursday Apr 24 2014

Update...
issued at 1108 PM CDT Thursday Apr 24 2014

Updated to include 06z aviation discussion below.

&&

Short term...(this evening through friday)
issued at 355 PM CDT Thursday Apr 24 2014

Rain was diminishing across the eastern half of the forecast area at middle
afternoon as a middle level low exited into northern Wisconsin. A band
of showers in the wake of this low was associated with an occluded
front. The showers will push east of the Twin Cities by late this
afternoon with the front moving through the forecast area by late this evening.
Scattered showers have developed over portions of the eastern
Dakotas this afternoon under the upper low. A few thunderstorms
can/T be ruled out in west central Minnesota into early this evening with a
few hundred j/kg of ml MUCAPE along with slightly negative Li/S.

Overnight...the main concern is how much fog develops and if it does
will it be dense. We certainly have the low level moisture and
the forecast hydrolapse for much of central and southern Minnesota is
favorable. However...there is uncertainty on how long substantial
wind will prevail during the night as the surface ridge axis moves
in late. Followed the hopwrf on developing fog tonight across much
of the forecast area while most short term solutions indicated very little fog.
It would seem the best place for the potential of dense fog
overnight is from central Minnesota on south to west of the Twin Cities.

Friday is shaping up to be a pretty nice day. Northwest winds will
increase to 10 to 15 miles per hour during the day. Abundant sunshine is
forecast across the Minnesota River Valley with high temperatures from
mix-down indicating middle to upper 60s. It will be cooler to the
northeast (lower 50s to lower 60s) where more cloudiness will
prevail.

Long term...(friday night through thursday)
issued at 355 PM CDT Thursday Apr 24 2014

The long term still looks to be dominated by a closed/cut off upper
low that will bring about a prolonged period of cloudy...rainy...and
cool weather to end April.

The evolution of the upper air pattern in the extended is quite
interesting as a couple of Rex blocks become major players for the
weather pattern across noam. The first will develop this weekend
over the North Atlantic. This causes everything upstream to
amplify...with a Sharp Ridge developing across central noam as deep
troughs flank it on the west and east coasts of the continent. At
the beginning of next week...the Rex block shifts west to central
noam...as the ridge this weekend builds north to western Hudson Bay. As
this happens...the western trough will absorb some energy from the eastern
trough as a cut off low develops over the central Continental U.S....due south
of the upper high in Canada. This is the pattern that will stick
with US much of next week. The European model (ecmwf) continues to offer the most
interesting demise of the central noam Rex block...with The Block
continuing its trek west next weekend...setting up over Alaska.

The long term will start off dry at the very least...but Saturday
will feature both increasing clouds and increasing east winds as a
surface low begins to deepen near the Colorado/KS/NE border in response to the
negatively tilted trough coming out of the southern rockies. As this is
happening...our increasing Erly low level flow will be pulling down
very dry air from a Hudson high...so continued keep things dry
during the day Saturday as the atmo below 700 mb looks to be setup
perfectly for virga. Instead...have likely probability of precipitation coming in south of
the Minnesota river Saturday night as the low to the SW drifts toward
central Nebraska...pointing a good surge of moisture transport and warm air advection
our direction. After that...get used to the clouds and rain. Though
model differences do exist with how far north the high/low centers
of the Rex block setup...the GFS/ECMWF/Gem all paint plenty of quantitative precipitation forecast
across the mpx County Warning Area Monday through Thursday. Though it obviously will
not be raining the entire...when doing 12 hour long pop groups...you
end up with a prolonged period of chance probability of precipitation for much of next week.
Run total qpfs from the Gem/GFS/ECMWF all paint 2 to 4 inches of
rain across the mpx area for next week...so will certainly be
setting a good base to the 2014 growing season.

For p-type...the vast majority of the precipitation will come in the form
of rain...but there will be the potential /mainly north of I-94/ to
mix in some wet snowflakes during the early morning hours depending
on how much we can cool down in the overnight hours. Though no
severe weather is expected /will be plenty of that to the
south/...best Li/S are negative along and south of the Minnesota River
Valley Sunday and Monday more or less...so will likely hear a few
rumbles of thunder as we get into the prolonged isentropic/fgen
forced precipitation event.

Unfortunately...what all of this cloud cover...precip...and east to
north winds means for US is that temperatures from Saturday through
Thursday of next week will be running a good 10 to 15 degrees below
normal. This will ensure that April continues our streak of below
normal months that started in November and will also require the
temperature in may to be well above normal to keep the Spring
/Mar-may/ from being below normal as well.

&&

Aviation...(for the 06z tafs through 06z Friday night)
issued at 1108 PM CDT Thursday Apr 24 2014

With a weak surface trough crossing the area expected to wash out near
the Minnesota/WI state line...the cloud edge of low stratus will linger
near the state border through the overnight hours...possibly
retreating slightly eastward. This means that the Minnesota taf sites will
remain mostly clear from clouds overnight while the WI taf sites
will be dealing with low stratus much of the night...especially Keau. In
addition...with plenty of rain having fallen in eastern Minnesota into western
WI...patchy to areas of fog will be a concern...again particularly
for the usual suspect of Keau but also pretty good confidence that
krnh will deal with a window of IFR conds. Have gone advertised as
such for both WI taf sites while going no worse than MVFR for the
Minnesota taf sites. Conds improve by late morning for all sites...
eventually returning to VFR by early afternoon and remaining there through
the rest of this taf cycle. Light/variable winds overnight eventually
become west to northwest by late morning and remain there...including becoming
a little gusty during the afternoon...before speeds diminish and
directions shift to NE.

Kmsp...mainly VFR for much of the 25/06z taf...with the only
exception being possible MVFR fog approaching daybreak. Not
expecting visibility below 4sm. Edge of low stratus will be sitting near
the Minnesota/WI state line through much of the night...but am not expecting
it to drift west and over the Airport...thus mitigating low stratus
concerns. Midlvl ceilings are likely late morning through much of the
afternoon...but still well within VFR...then sky clear conds likely late Friday
night into Sat morning. Winds become breezy/gusty from the northwest tmrw
afternoon...then settle down to 5-10 knots from the NE tmrw night.

/Outlook for kmsp/
Sat...VFR. NE winds 10-15 kts.
Sun...mainly VFR. MVFR conds possible in -ra. East winds 15-25 kts.
Monday...MVFR/IFR -ra br. East winds 15-25 kts.

&&

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

$$

Update...jpc
short term...trh
long term...mpg
aviation...jpc