Scientific Forecaster Discussion
fxus64 kmeg 240302
Area forecast discussion
National Weather Service Memphis Tennessee
1002 PM CDT Wed Oct 23 2019
Surface high pressure is situated over the southeast US with clear skies
and light winds across the mid-south. Good radiational cooling
conditions will allow temps to fall in the lower to mid 40s in the
Delta Region and around 40 toward the Tennessee River. A few cooler
sites across west Tennessee could see some upper 30s. Forecast looks
Previous discussion... /issued 344 PM CDT Wed Oct 23 2019/
A broad trough sits over much of the Continental U.S. This afternoon with
the strong vortex anchored over northern Ontario. A shortwave
trough is moving east across the northern plains, with a strong,
southwesterly polar jet on the southern flank of this wave. Dry
air aloft prevails over our neck of the Woods, providing sunny
conditions across the mid-south. Temperatures are near normal this
afternoon, primarily in the lower 70s. Winds have been a bit
gusty across the Delta in response to a surface low traversing Iowa
at this time.
We'll see another chilly night across much of the mid-south given
the light winds, clear skies, and dry air. However, it should be a
few degrees warmer than last night with lows near 40f in the Tennessee
Valley and in the low/mid 40s elsewhere across the County Warning Area. Expect
another pleasant day tomorrow although cloud cover will begin to
increase as the next wave approaches. Highs on Thursday will be in
the upper 60s and lower 70s.
Weather conditions look to turn south on Friday as the shortwave
trough currently diving southeast across the northern rockies cuts
off to our west and moves slowly toward the MS valley through
Saturday. A surface low is progged to develop near the mouth of
the Sabine River along the Gulf of Mexico early Friday, keeping
the mid-south well north of the warm front. Isentropic ascent
and the approaching warm front aloft will assist in the
development of scattered to numerous showers on Friday, with
rain chances increasing Friday night.
The surface low is forecast to lift to the north-northeast Friday
night, with the warm front perhaps moving as far north as I-40 by
12z Saturday. The greatest chance for thunderstorms will be south
of the front where instability will be the greatest. However,
there may be enough elevated instability to support a few rumbles
of thunder Saturday afternoon. The severe weather threat remains
relatively low at this time, but we will continue to monitor the
instability trends. Locally heavy rainfall may be more of an
issue. Widespread rainfall of 1-3 inches is expected across the
mid-south and there may be localized higher amounts, especially
across northeast MS.
Rain chances will continue through Saturday as moisture wraps
around the backside of the slowly departing cyclone, but
conditions are expected to gradually improve by mid afternoon.
Lingering rain chances will give way to dry weather by Sunday
morning as surface high pressure builds into the region.
The remainder of the forecast period is highlighted by significant
uncertainty. The global models remain at odds with the evolution
of the synoptic pattern next week. The progressive GFS brings a
fast-moving trough across the region on Monday, providing another
shot at light rain followed by a cold front. The European model (ecmwf) and CMC
both hold this trough back over the western Continental U.S. Until midweek,
with generally dry weather Monday and increasing rain chances
Tuesday and Wednesday. The 12z European model (ecmwf) (and most of the gefs)
ensemble members are largely dry with this Monday system, lending
more credence to the slower solutions. Thus, will maintain a dry
forecast on Monday with only 20-30% pops Tuesday and Wednesday.
Extended temperatures during the forecast period will remain below
normal for the most part with highs in the 60s most days. Lows
will generally be in the 40s and 50s, although some areas may dip
into the 30s by early next week.
00z taf cycle
VFR conditions will continue for the entire forecast period. Winds
will be mainly from the south at around 5 knots tonight before
shifting to the southeast at around 5 knots on Thursday.