Area Forecast Discussion
Issued by NWS Springfield, MO
FXUS63 KSGF 262121
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPRINGFIELD MO
321 PM CST Thu Feb 26 2015
.SHORT TERM...(This Evening through Friday Night)
Issued at 308 PM CST THU FEB 26 2015
An Arctic airmass continues to advect into the area this
afternoon, with temperatures topping out in the mid 20s in most
locations. With a steady north winds across the region, wind
chills have remained in the teens.
Deep high pressure, currently centered over northeastern Montana,
will build south through the Missouri River basin tonight into
tomorrow morning. This should set the stage for a very cold night
tonight, with lows ranging from around 10 degrees across
southeastern Kansas and far southern Missouri, to the single
digits across central Missouri and the eastern Ozarks. With the
center of the high remaining just to our north throughout the
night, a light northeast to easterly breeze will be maintained
overnight. This will help drop wind chills to between 5 and 10
below zero in most locations.
That cold, and dry, airmass will slowly translate east tomorrow,
with temperatures on Friday only in the low 20s. An area of
light snow will try to impinge on the area from the southwest
tomorrow afternoon and evening, but it`s not clear at this time
whether the magnitude of the dry air will be too great to keep
anything of significance from making it into the CWA. Will
maintain a very low end chance for light snow over the
southwestern portions of the forecast area Friday afternoon and
Temperatures Friday night should then fall back into the teens, as
winds become southeasterly with time.
.LONG TERM...(Saturday through Thursday)
Issued at 308 PM CST THU FEB 26 2015
A very active pattern is expected from this weekend into the
middle of next week as an upper level trough of low pressure
deepens over the western U.S. and puts the Ozarks in an increasing
southwesterly flow aloft. The first time period of concern will be
from Saturday into Saturday night as multiple weak short wave
troughs eject across the central Plains and towards the Mid-
Mississippi Valley. While those waves will provide some weak upper
level lift, the main lifting mechanisms will be in the lower and
middle levels of the atmosphere as isentropic upglide overspreads
Expectations have not changed much...with precipitation onset
expected from west to east from Saturday into Saturday evening.
Precipitation will initially be in the form of snow with perhaps
some sleet mixed in at onset. Models do then bring a warm nose
into southern Missouri starting Saturday evening and progress it
north into Sunday morning. Models do differ on how far north this
feature will make it...along with some timing differences.
Nevertheless, confidence continues to increase that we will see
light freezing rain potential spread from south to north
throughout the period. Precipitation may then change to rain from
south to north on Sunday as temperatures warm into the upper 30s
to lower 40s. While precipitation should tend to taper off into
Sunday night, some very light precipitation (in the form of rain
or freezing rain) will remain possible.
As for snow and ice accumulation amounts, current expectations are
for a general 1-3" swath north of a Cassville to Winona line.
The heaviest totals would be across west-central Missouri and back
towards the Fort Scott, Kansas area. We could see amounts push 4"
over parts of that area. Ice accumulations are expected to remain
below a tenth of an inch. We painted the "highest" amounts
generally along and south of a Pittsburg, Kansas to Salem,
Missouri line where confidence is highest regarding warm nose
intrusion. Accumulations may need to be increased across central
Missouri if confidence increases that the warm nose will make it
that far north.
While we may see a break in the action from later Sunday night
into early Monday, it will be short-lived. The upper level flow
will continue to amplify with the Ozarks becoming firmly
established in a southwesterly flow aloft. Global models have
increased their trend towards a warmer solution as precipitation
once again overspreads the area from later Monday into Monday
night. If this trend holds, this should support mainly liquid
precipitation. Interestingly, models are actually showing a pretty
decent signal for returning moisture from the Gulf of Mexico and
resulting instability. We have therefore introduced a chance for
thunder. We have also continued the trends of warming temperatures
as we get into Tuesday. One item we will have to watch is hydro as
this pattern would support decent rainfall potential.
Global models then depict some sort of trailing wave which could
extend precipitation chances into the Wednesday or Thursday time
frame. Confidence is low on whether or not this will occur, so we
kept PoPs in the 20-30% range once we get beyond Tuesday night.
After what may be a mild Tuesday, temperatures will cool off by
Wednesday and Thursday.
.AVIATION...(For the 18Z TAFS through 18Z Friday Afternoon)
Issued at 1115 AM CST THU FEB 26 2015
VFR conditions are expected through mid day tomorrow at all
terminals. High pressure will sink south-southeast across the
Missouri River Valley tonight, resulting in northerly winds
becoming northeast with time, and eventually easterly by mid day
tomorrow. Sct high level clouds will remain across the region,
with some mid level clouds beginning to move into far southwestern
Missouri by very late in the TAF period on Friday.