Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
654 PM CDT Monday Apr 20 2015
Update...for 00z aviation discussion below
Short term...(this evening through tuesday)
issued at 334 PM CDT Monday Apr 20 2015
A few rain...snow...or sleet showers have developed this
afternoon across western and southern Minnesota. Brief reductions
in visibility has been the main impact...particularly with the
snow showers...but no accumulation has been reported. These
showers will wane across southwestern Minnesota...but should continue and become
more numerous late tonight and Tuesday north of I-94 as the main
piece of energy swings through. There may be up to a half inch of
snow under the more persistent snow showers late tonight across
northeast Minnesota and northwest WI.
Winds have not been too impressive today...probably due to
shallower mixing brought on by extensive cloud cover. Winds will
remain elevated tonight with gusts of 20 knots continuing...and with
cloud cover remaining overhead...temperatures will hold in the
low to middle 30s. Mixing up to 800 mb Tuesday only yields highs in
the low 40s...so lowered temperatures a bit.
Long term...(tuesday night through monday)
issued at 334 PM CDT Monday Apr 20 2015
Large scale pattern evolution...
We will see things very slowly progress over the course of the
week... as the upper trough over the central/eastern part of the
continent slides east and eventually gives way to westerly/zonal
flow by the weekend.
Forecast item/S/ of concern...
We/ll continue to deal with some lingering rain showers/flurries across the
eastern forecast area on the backside of the departing surface low
through Wednesday. However... precipitation amounts will be limited. Below
freezing temperatures will likely occur each night during the
middle of the week... which could cause issues for any sensitive
plant which may already be growing.
Main differences in the guidance is from Friday into the weekend...
with the European model (ecmwf) a bit quicker with return flow and potential precipitation
moving back into the area. The Canadian offers somewhat of a
compromise in timing between the European model (ecmwf) and slower GFS. The gefs mean
is very similar to the operational GFS... although there is a fair
degree of spread in the solutions. Given the differences and lack of
confidence in any specific solution... did not make any substantive
changes from the consensus/blended guidance.
Sensible weather expectations...
Lingering rain showers/flurries into Wednesday across the east... otherwise
dry with slowly moderating temperatures as the upper trough and
surface ridge slowly slide east over the course of the week.
Introduced some chance probability of precipitation in from the west/southwest Sunday into
Monday... although if the quick European model (ecmwf) pans out that may need to be
sped up a bit.
Aviation...(for the 00z tafs through 00z Tuesday evening)
issued at 655 PM CDT Monday Apr 20 2015
Scattered showers /rain and snow/ across northern and central Minnesota
will continue filtering south-southeast across the taf area this
evening...with additional development mainly across central Minnesota
and western WI continuing through Tuesday. This will result in
prolonged vcsh mentions given the showers will be fleeting and
any impacts brief. MVFR ceilings over northern Minnesota will gradually sink
south and east across the area as well...with all sites except
krwf seeing a ovc020-030 deck prevail through the overnight hours.
Improvement to a low-end VFR ceiling is expected to occur during the
middle to late morning hours of Tuesday...with the exception of WI
sites /krnh and Keau/ where prolonged MVFR ceilings and more shower
activity is expected into the afternoon. West/northwest winds
stay gusty through the period...with only minor nocturnal
expect rain and even some snow showers in the vicinity of the site
tonight. No accumulations however. By 15z Tuesday...activity is
expected to be to the north-northeast of kmsp. Ceilings become MVFR
/circa 2500 feet/ this evening through around 15z Tuesday. Wind gusts
decrease only slightly this evening...then increase again by late
/Outlook for kmsp/
Wednesday...VFR. Winds northwest 15g25kts.
Thursday...VFR. Winds northwest 10-15kt.
Friday...VFR. Winds NE 5-10 knots.