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fxus64 kmeg 202322 

Area forecast discussion
National Weather Service Memphis Tennessee
522 PM CST Wed Nov 20 2019

see the 00z aviation discussion.


Previous discussion... /issued 330 PM CST Wed Nov 20 2019/

a progressive split upper level pattern will prevail over the
lower 48 states into early next week, bringing a couple of rain
events to the midsouth. Arctic air will remain bottled up over the
central and northern plains. A brief, glancing pass of colder air
may extend down to the mid-MS river by the middle of next week.
Bottom line for the midsouth: little to no chances of Arctic
intrusions and temps not far from late November norms.

Our first rain event will extend over a two day period. A lead
shortwave will track from a closed low over the Desert Southwest
into the upper Midwest early Thursday. A weak trof axis will
extend south of the shortwave through the Ozarks. Forcing will
remain on the weak side initially, but subtropical moisture plume
carrying 1.5 inches of precipitable water will accompany the trof
as it lifts through the midsouth on Thursday. NAM bufr sounding
depict insufficient instability for mention of thunder.

A cold front will drop through the mid-MS River Valley Thursday
night, behind the exiting shortwave. This will be about the time
the closed low lifts into the plains, strengthening a downstream
upper level speed Max from the arklatex through the southern Ohio
Valley - roughly overlaid across the surface cold front. An
initial corridor of persistent light to moderate rain will likely
set up along the front north of the I-40 corridor, then follow the
front as it sags south behind an exiting shortwave Friday
afternoon. Model consensus on rainfall exit timing is a bit
lacking, but a blended solution ends the rain with the intrusion
of a midlevel dry slot late Friday night. Most of the midsouth is
expected to receive 1.5 to 2 inches of rainfall across the
Thursday morning through Saturday morning period. Dry and cool
Pacific surface high pressure will prevail from Saturday afternoon
through Monday.

Strengthening southerly flow will return modified maritime air to
the midsouth Monday night, in advance of an upper trof lifting
through the Central Plains on Tuesday. While the operational GFS
maintains a deeper closed low, the GFS ensemble mean depicts an
open trof, similar to the European model (ecmwf). The implications for the midsouth
would be a reduced (though still non-zero) severe weather threat
on Tuesday, compared earlier model solutions. Still plenty of time
for additional guidance changes.



/00z tafs/

Mid/high clouds will increase tonight with ceilings gradually
lowering through the morning hours. Light showers will develop
around or after 12z but coverage/intensity will remain scattered
much of the day. MVFR ceilings are expected in jbr by late morning
at at mem/mkl around 00z. There is a potential for these ceilings
to arrive slightly earlier if rain develops more quickly. Finally,
a southerly low-level jet will intensify to 30-35 kts late
tonight, increasing southerly surface winds throughout the day.



Meg watches/warnings/advisories...

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