Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Sioux Falls South Dakota
616 am CDT Friday Mar 14 2014
Short term...(today and tonight)
issued at 425 am CDT Friday Mar 14 2014
A mild well mixed day ahead as slightly cooler air settled into the
area overnight. The main concern today ill be fire weather over the
southern and western part of the County Warning Area. Not seeing any threat for red
flag conditions but with sustained winds likely close to 20 miles per hour at
times should be a solid very high. Otherwise did not change
temperatures very much with middle 40s over the remaining snow cover in
southwest Minnesota and middle 50s along the Missouri River valley.
Skies should be partly cloudy to mostly sunny but a period of mostly
cloudy will be possible over southwest Minnesota this morning.
Clouds will increase overnight and winds will turn to the east and
northeast as low pressure develops to the west. This will help drag
somewhat cooler air into the area as lows fall into 20s in the north
and around 30 in the south. A very small chance for light snow or
flurries exists in the far northeast County Warning Area as middle level moisture
builds in but not expecting much before sunrise.
Long term...(saturday through thursday)
issued at 425 am CDT Friday Mar 14 2014
For the most part...Saturday will mark the start of a more active
period of late winter weather at the larger scale pattern and a
very active Pacific wave train suggest several systems moving
through the region. The initial system will start on Saturday
morning...with a weak impulse glancing the northeast County Warning Area. Will be
a fairly dry low level wedge to overcome...but some concentrated
frontal lift could bring a little very light snow/flurries to the
far northeast around kmml or kmwm during the morning. Stronger
dynamical system will push in during the afternoon...while low
level thermal gradient starts to collapse southward. This colder
air will likely bring a slowly falling trend with increase in
clouds working southward. Have accelerated the initiation of
precipitation into areas west of i29 and eastward into SW Minnesota
during the afternoon. Thermal profiles would suggest mainly
rainfall for the far south...perhaps a little rain before a quick
change to snow farther northward. Not looking at any great
indication of instability aloft with system...and much of the lift
seems to be a little lower in the profile and away from a fairly
shallow dendritic zone. Expect that overall will have fairly
modest snowfall amounts...generally from 0.5 to 1.5 inch range...
but perhaps locally up to a couple inches in parts of i90 SW Minnesota
into northwest Iowa. Precipitation expected to wind down fairly distinctly from
north to south as drier air wedge pushes southward from Minnesota
and northeast South Dakota during the later evening and overnight.
Should be a fairly significant thermal gradient across the County Warning Area
from a more cloudy north to more sunny south...and could see 20 or
more degree difference from north to south by midday...which will
start to work itself out with temperature falls during the afternoon.
On Sunday...while could be a little lingering light snowfall in
the extreme southeast early...should be a fairly quiet rest of the
day as cool high pressure slides east of the County Warning Area. Will make for a
fairly big struggle to temperatures most locations other than the far
west which should reach close to seasonal numbers. Increasing
south to southeast winds overnight will bring a steady to rising
trend overnight...and within warm advection zone may be dealing
with a few hours of light precipitation threat. For now have gone
with only snow...but with as much as some temperatures aloft indicated to
warm... without any evaporative cooling... may get some mixed type
in parts of SW Minnesota for a while.
Jet energy will begin deepening low pressure in the Western Plains
through the day on Monday. Fairly strong warm frontal boundary
will set up somewhere near the Missouri Valley through the
day...with leading surge of warm air advection perhaps bringing a
few light rain showers north of Interstate 90. Highs again could
be fairly diverse...from middle 40s northeast to around 60 southwest.
Certainty has definitely increased as far as development of a late
winter storm system in the plains states surrounding Tuesday...with
almost every solution now indicating a system around our longitude.
A wide diversity of operational solutions and ensemble spread...
but some potentially interesting storm structure/dynamics may be
in play with perhaps an inverted trough/trowal evolving with
system that could help focus better than nuisance precipitation.
Have played things a bit more broad brushed at this point...
hedging somewhat higher on probability of precipitation...a bit lower in diurnal range...
and moved a bit more into the snow end of things...especially north
and west from later Monday night into Tuesday. Depending on track
and intensity of wave...which varies from north in European model (ecmwf) to south
in Canadian...well envisioned in the ensemble solutions...could
have a fairly significant system with even some potential for
freezing rain on Monday night/early Tuesday. A lot of details to
shake out...so be sure to stay updated on changes over the next
few days...but Worth a stronger long range mention at this point.
To be consistent...knocked a few temperatures back on highs Tuesday...
and increased clouds/winds around system for about 36 hours.
Aviation...(for the 12z tafs through 12z Saturday morning)
issued at 614 am CDT Friday Mar 14 2014
VFR conditions through the period at each of the taf sites. Some
MVFR ceilings will be possible over parts of southwest Minnesota