Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
600 am CDT Sat may 25 2013
Short term...(today and tonight)
issued at 344 am CDT Sat may 25 2013
Initial shield of warm air advection showers that was depicted well on 310k
isentropic surface on the NAM/GFS is fading away across western WI as this
batch of forcing weakens and dives southeast. In its wake...we have
warm air advection at 850 mb...but the deeper moisture has pushed east...so precipitation has
cut off pretty quick. With the warm air advection and weak moisture
transport...should be able to get some light showers/sprinkles
across Minnesota this morning...but not much more than that.
Best chance for rain today will be across southern Minnesota. Warm front now can
be found across south central Nebraska into NE kan...with a strong low level jet
overrunning it. This has generated an mesoscale convective system over eastern Nebraska this morning.
Thunder starting to increase across Iowa as well as the low level jet has slowly
worked east. Most of this thunderstorm activity will remain south of
Minnesota through the day...but all hi-res models show some of this
moisture from Iowa sneaking up into south central Minnesota through
morning...where some high chance/likely probability of precipitation are continued through
the morning hours. For the afternoon...precipitation looks to shut
off...but we will be stuck with fairly broad cloud cover...with the
only hope for some breaks across the NE mpx County Warning Area thanks to the
influence of a dry surface high that will be splayed out across the
Great Lakes. Given the cloud cover will be a cool day...with
temperatures in south central Minnesota likely staying in the 50s thanks to
better rain chances and thicker cloud cover.
For tonight...all models show another round of convection riding
along north of the warm front...kind of like what we have seen
overnight to our southwest. Question becomes how far north does the
activity make it. Consensus placement from the warm front places it
by 12z Sunday morning from the Black Hills...down through
Yankton...South Dakota and then down to the central Iowa/MO border. Once
again...will see a low level jet overrunning this frontal feature...which
should generate yet another mesoscale convective system. Given the fronts placement to our
southwest...best chances for thunderstorms tonight will be south of
the upper Minnesota river in SW Minnesota into SC Minnesota. For timing...favored highest
probability of precipitation to after 6z...as convection should fire this evening over southeast
sodak into NE Nebraska...then head toward SW/SC Minnesota. All of this activity
would be elevated...so severe threat looks minimal...with the main
impact being the potential for heavy rain...as we have seen this
evening in Nebraska.
Long term...(sunday through friday)
issued at 344 am CDT Sat may 25 2013
The long term period continues to look increasingly wet and
stormy. This is due to the region being sandwiched between a
building upper high along the eastern Seaboard... while a very
deep trough pushes into the western half of the United States.
There should be a round of convection pass across southern Minnesota
Sunday morning...very similar to what has been ongoing overnight
across NE/IA. The storms to our south currently have been basically
sub severe... but very efficient rain producers... with upwards of
1.75 inches of rain in three hours. This is the trend expected
Sunday morning across southern Minnesota... especially the I-90
corridor. Thereafter... a significant diminishing trend in the
precipitation for Sunday afternoon and evening with the nmm/arw
WRF/S in agreement.
Memorial Day is looking a little worse now with even the European model (ecmwf)
driving a wave of convection across the forecast area during the day and
evening. Just general thunder indicated on swody2 which seems
reasonable with the main warm frontal boundary meandering from the
Central Plains to the lower Ohio Valley. Again... the concern will
be localized heavy rainfall. The deterministic runs would also
suggest another round of convection for US late Monday night and
Tuesday morning... especially across southern Minnesota.
This repeating rounds of potential convection is disturbing with
areas of southern and especially southeast Minnesota running well above
normal on rainfall for the month of may. The threat for flash
flooding will be on the increase. It was pointed out on Friday
in the weathertalk from Dr Seely at the umn that since March
1st...(meteorological spring) it has been one of the wettest in
history for many areas of Minnesota. Add this to the cips analogs
for 5 days from now and one sees a very wet pattern across all of
the region with 2 inches of rainfall exceeding 30 percent
probability with even widespread 3 inches having a 10 percent
probability. This is in addition to the rains Sunday through
Tuesday. Not surprising then are the run totals from the GFS and
European model (ecmwf) through next Friday which paint the landscape with 2 to 4
inches of rain... with 4 inches or more south of US. Digressing
for a moment... one of the months/years that has shown up in the
cips analogs recently is July 1993... with record flooding in this
part of the country. A review from ncdc showed low pressure aloft
over the western High Plains with a strong SW jet at 250 mb across
our area. The Bermuda high had pushed into the southeast United
States with organized 850 mb winds from the western Gulf of Mexico
to the western Great Lakes. Hence... the flooding potential is a
big concern for the week ahead as the pattern in the Summer of
1993 mimics our week ahead quite well.
Finally... and just as important... will be the threat for severe
weather next week as the warm front lifts north into our area
beginning on Tuesday. Not too concern about severe on Sunday. The
chance increases some on Monday (isolated)...especially if
afternoon convection develops as deep layer shear rises. Then from
Tuesday Onward there is severe potential each day. The cips
analogs contain many severe reports for US for the middle of next
week with severe probabilities from 15 to 30 percent for the
entire forecast area using the top 8 analogs. A cold front may move across
the forecast area from Friday into Saturday...diminishing the severe weather
threat.
&&
Aviation...(for the 12z tafs through 12z Sunday morning)
issued at 600 am CDT Sat may 25 2013
Lots of convection on the radar...but it is all well to the south.
May see a few sprinkles/light showers across Minnesota through the
morning...with anything more substantial staying confined to the
I-90 corridor. For the rest of the day...will have to track MVFR
ceilings emanating from the thunderstorms and rain activity in Iowa. Continued to favor a
hrrr/rap depiction for the handling of these low clouds...keeping
MVFR ceilings during the day confined to rwf. With southeast flow...NAM along
with the rap show MVFR ceilings working northwest into nodak...which should
bring MVFR ceilings to axn this afternoon or evening. Msp/stc look to be
sitting on the edge of the MVFR ceilings by the end of the taf period
and at this point...stuck with VFR conditions at both locations
throughout...though certainly some MVFR ceilings could be seen after
06z. Expect another round of thunderstorms tonight...though with
warm front drifting north...storms Saturday night should be a bit
farther north of where they are now. Best chance for thunder looks
to be along/south of the Minnesota river...so introduced some thunderstorms in the vicinity to the
end of the rwf taf. For winds...they will be remarkably persistent
this period out of the southeast...with winds today expected to
increase to near what was seen Friday across Minnesota.
Kmsp...confidence high in taf through 06z. After 06z...MVFR ceilings
that will be southwest of the field will start to push northeast and
could begin to impact the field. However...sticking with the theme
of the GFS...with ceilings remaining above 4k feet. Will also have to
watch how activity evolves to the southwest late tonight...as there
are indications from the GFS/European model (ecmwf) that some light activity could
approach the field Sunday morning. However...at this time...with the
warm front expected down across central Iowa...feel better rain showers/thunderstorms and rain
chances Sunday morning will be down across south central Minnesota...so
kept any sort of precipitation mention out of the taf.
/Outlook for kmsp/
sun...chance MVFR or lower ceilings. Chance shra/tsra. Winds southeast 10-15 kts.
Monday...chance MVFR or lower ceilings. Chance shra/tsra. Winds southeast 10 kts.
Tuesday...chance MVFR or lower ceilings. Thunderstorms and rain likely. Winds south-southeast 5-10 kts.
&&
Mpx watches/warnings/advisories...
Minnesota...none.
WI...none.
&&
$$
Short term...mpg
long term...rah
aviation...mpg
