Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
1242 PM CDT sun Oct 4 2015
Short term...(today and tonight)
issued at 255 am CDT sun Oct 4 2015
Today Marks the beginning of a pattern change...as southwest flow
develops upstream of the upper low along the California coast.
Clouds will increase ahead of this feature...and a weak ripple of
energy at the middle levels of the atmosphere will eject across west
central to northern Minnesota today. The lower levels are fairly dry
however...so any precipitation that falls will be light in
intensity/amount...and really only deserving of a 20 pop.
Surface winds /mixing/ will be lower today than Saturday...and given
the increased cloud cover...expect high temperatures to top out in the
upper 50s to lower 60s. More cloud cover tonight will keep frost
concerns at Bay...wit readings in the 40s expected.
Long term...(monday through saturday)
issued at 255 am CDT sun Oct 4 2015
A split flow regime will be noted in the extended period /Wed Thursday
Friday/ which gives uncertainty on phasing of the southern/northern
jets. Although a potent weather system is likely to move across the
northern plains/upper Midwest late Wed/Thu...the phasing of the
jets will lead to uncertainty of the surface low development...speed
of the short wave trough and precipitation field. Both the ec/GFS
have more influence on the northern jet and associated surface
low...but timing differences are noted with the ec slower. The Gem
has more influence on the southern jet and holds back the energy
of the northern stream until late in the week. Ec/GFS are more in
line of a more progressive short wave leading to the precipitation
to move out of the region by Friday. However...if the Gem has a
better handle on the phasing of the jets...the precipitation could
linger into Friday and possibly Saturday.
Other than the precipitation chances late in the week...the upper
air pattern will be more conducive for much milder temperatures /drier/
next weekend...and possibly lingering into the week of the 12th.
The mean upper air pattern next week is very similar to an El Nino
pattern across the Gulf of Alaska with a broad long wave trough
/anomaly low surface pressure/. This will keep unsettled conds from
the northwestern Continental U.S. And into the Gulf of Alaska. This will also
leads to the polar jet further north across Canada. This is a
warmer and drier pattern for the upper Midwest. Until there is a
pattern change in which the long wave trough holds in the Gulf of
Alaska...our weather will be influence by more mild zonal/SW flow.
Aviation...(for the 18z tafs through 18z Monday afternoon)
issued at 1240 PM CDT sun Oct 4 2015
Fairly thick coverage of cumulus clouds has recently developed
over eastern Minnesota and west central WI...and with cloud bases around
2500-3000 feet and broken coverage...MVFR ceilings could persist for the
next few hours. VFR is likely to return to all terminals by
sunset. However...guidance is becoming more favorable for a
stratus deck to push northwestward over the eau and rnh terminals
overnight through Monday morning. MVFR ceilings are once again
possible at these sites after 06z. Winds will remain light across
the region...generally out of the southeast through tonight becoming
southerly on Monday.
Kmsp...a broken deck of low cumulus clouds has quickly
developed...and MVFR ceilings are currently occurring at the terminal.
While these clouds could certainly become more scattered in the
next couple hours...cannot rule out MVFR ceilings during the early
evening. These low clouds will dissipate by sunset...and VFR is
likely for the rest of the period. However...a stratus deck is
expected to develop just to the southeast of msp between 09z-15z...so
there is a slight chance that MVFR ceilings could occur during that
time as well. Winds will remain light...veering from the southeast
tonight to southerly on Monday.
/Outlook for kmsp/
Monday...VFR. Wind S 5-8 kts.
Tuesday...VFR. Wind SW becoming northwest 5 kts.
Wednesday...VFR. Chance -shra late. Wind east-southeast 5-10 kts.