Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Memphis Tennessee
527 am CST sun Mar 1 2015
updated for 12z aviation discussion.
Previous discussion... /issued 427 am CST sun Mar 1 2015/
Currently...inverted surface trough extends from the lower MS
valley into north MS and west Tennessee. NE Arkansas and the MO bootheel
on the cold side of this feature and light north winds continue to
advect 30-32f temperatures into that area. Meanwhile light overrunning
precipitation continues across the northwest half of the forecast area. This
precipitation is falling in the form of light freezing rain where temperatures
are sub freezing. Given the latest surface temperatures on the mesoscale plots
decided to add the bootheel and Cross County to the Winter Weather
Advisory and extend it out to 9 am CST. No significant icing
accumulations expected just a light glaze in spots with some slick
areas on roads.
Today...an upper level disturbance moving through the middle MS
valley will help generate lift over the relatively cool airmass
at the surface across the midsouth. 850 mb winds increase to 30-35
kts by 18z. Rain will continue to increase in coverage today and
gradually shift east and southeast as the low level jet veers from south-southwest to west by
00z. Undercut temperature guidance across NE Arkansas and the MO bootheel where
the NAM seems to have a good handle. Elsewhere highs will range from
the middle 40s to middle 50s.
Tonight...high pressure starts to build in with precipitation tapering
off across the north. The best chances for rain will be over north
Mississippi where a developing frontal boundary will continue to
generate some overrunning through the night. Across the northern tier
could see some light freezing rain late tonight into early Monday
as temperatures drop to around freezing.
Monday...looking relatively quiet with high pressure centered over
the middle MS valley and a stationary front south of the region.
Lingering rain possible over north Mississippi but this should be
tapering off as some ridging aloft moves in. Temperatures will be cool
with highs in the 40s.
Monday night and Tuesday...stationary front near the Gulf Coast
will lift north as a warm front Monday night into Tuesday with
showers and a few thunderstorms possible by Tuesday afternoon as
surface temperatures climb into the 60s to around 70 and surface
dewpoints top 60 over much of the area. Potential for strong or
severe storms still appears low as overall instability is very
Tuesday night through Wednesday night...still looking very
interesting. The 00z European model (ecmwf)/06z GFS/06z NAM pushing the cold front
through late Tuesday night into Wednesday with rapidly falling
temperatures. The positively titled upper trough hangs well back to the
west while strong...moist SW flow aloft continues over the region
after the cold front moves through. This points toward a good
deal of Post frontal precipitation. The 00z European model (ecmwf) is very aggressive with
well over an inch liquid behind the front while the 06z GFS has
less but still a significant amount. Will gradually transition
from rain to freezing...sleet and the snow as the cold air depth
deepens from northwest to southeast Wednesday into Wednesday night. Too early to
talk about amounts but significant winter precipitation seems possible
over at least part of the midsouth. Expect precipitation to taper off
Wednesday night as upper trough finally pushes though. Arctic
airmass building in will drop temperatures into the upper teens and lower
20s by Thursday morning.
Thursday through Saturday....very cold for end of the week with
some warming by the weekend though still below normal. A
disturbance moving out of Texas may bring some rain to southern
areas by later Saturday.
Occasional -fzrapl early at jbr...otherwise the sites will
experience scattered rainshowers. Most will be light...but this
afternoon a few may become moderate. MVFR/VFR ceilings initially will
lower to IFR/MVFR. Winds will be light and variable...but a
passing cold front will align them from the northeast late. Wind
gusts of 16-22 kts can be expected during the late night.
Arkansas...Winter Weather Advisory until 9 am CST this morning for Clay-
MO...Winter Weather Advisory until 9 am CST this morning for Dunklin-