Scientific Forecaster Discussion
fxus64 kmeg 121118
Area forecast discussion
National Weather Service Memphis Tennessee
518 am CST Tue Dec 12 2017
Previous discussion... /issued 313 am CST Tue Dec 12 2017/
currently a well mixed boundary layer was keeping temperatures
milder tonight in the wake of yesterday's evening frontal passage.
Readings ranged from the mid 40s to 50f. Winds speeds were
generally in the 10-20 mph range with skies mostly cloudy.
Today through Friday...northwest flow aloft will keep the
midsouth dry...with the passage of two more distinct disturbances
that will see-saw temperatures below and above normals. The next
shortwave will arrive tomorrow evening...so after a cooler start
today temperatures will warm a good 7 to 10 degrees for highs
Wednesday. Reinforcing cooler air will surge back into the area
Thursday and Friday as the next shortwave ripple dives southeast
from the Dakotas. The GFS continues to show a period of stronger
lift Friday that may squeeze out sprinkles or morning snowflakes.
The overall greatest concern the next four days will be an
elevated fire danger. Today's afternoon rh's will drop into the
mid 20's to low 30's..but fortunately the 20ft winds will have
weaken to below redflag criteria. Slightly greater humidity is
anticipated tomorrow through Friday...but the persistent dry
weather could keep the area primed for a continued fire danger.
Saturday through Monday...the GFS has been consistently showing a
change in the pattern...with the upper level flow backing
southwesterly as a trough digs into the southern rockies. This
will provide for a northern surge of midlevel subtropical and low
level Gulf moisture from Texas. The current 00z run from the
European model (ecmwf) has gotten on board with this thinking...and has gone even
further in showing the trough getting pinched off from the main
jetstream across the north. Either solution will bring about a
welcomed 36 hour window for rain. The weather prediction
center...along with several of the gefs solutions show the brunt
of this precipitation occurring south of I-40...where upwards of
an inch could be seen. The euro's 500mb cut-off low would provide
the whole area this soaking. Have increased pops starting
Saturday night through Monday morning...and added the threat for
fog as well...which could become dense. Temperatures this period
will be above normal with readings remaining above freezing.
Patchy midlevel clouds will dissipate early this morning. Winds
will be from the north to northwest 10-15kt with gusts near 20kt
today...diminishing to 5-10kt overnight. Winds will shift from the
southwest early tomorrow. VFR conditions will prevail.