Area Forecast Discussion
Issued by NWS Memphis, TN

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FXUS64 KMEG 220433 AAA
AFDMEG

Area Forecast Discussion...UPDATED
National Weather Service Memphis TN
1133 PM CDT Sun Oct 21 2018

.UPDATE...
Updated for 06Z Aviation Forecast Discussion below.

&&

.PREV DISCUSSION... /issued 944 PM CDT Sun Oct 21 2018/

UPDATE...

Temperatures are in the upper 30s and lower 40s at this hour.
Latest surface analysis places a 1026mb high pressure center along
the Mississippi River in the heart of the Mid-South. As a result,
winds have gone completely calm across the entire forecast area.
Radiational cooling will continue through tomorrow morning with
lows dropping into the mid to upper 30s areawide. The current
dewpoint field has recovered over the past few hours with most
readings mainly in the upper 30s. As temperatures fall to the
dewpoint, frost will begin to form on grass and some elevated
surfaces and the dewpoint should fall another couple of degrees.

The one question was, "will temperatures still fall to near
freezing in the freeze warning with dewpoints still in the upper
30s?" The short answer is maybe, as some deposition should allow
the dewpoints to fall a few more degrees. MOS guidance has not
resolved the mass field well, but that`s okay because heavy frost
is still expected in the freeze warning area anyways.

Didn`t make any big changes to the forecast. The frost advisory
and freeze warning are in good shape. New zones and grids are now
available.

AC3

PREV DISCUSSION... /issued 325 PM CDT Sun Oct 21 2018/

DISCUSSION...Surface analysis this afternoon places a 1028 mb
ridge of high pressure over the Mid South. This has resulted in
sunny skies and cool temperatures in the 50s at most locations.
Frost/freeze potential late tonight into early Monday morning and
rain chances for the latter half of this week are the predominant
forecast challenges in this afternoon`s forecast issuance.

The aforementioned ridge of high pressure overhead will result in
clear skies, light to nearly calm winds, and temperatures dropping
into the lower to middle 30s across many locations overnight into
early Monday morning. Current short term trends suggest
temperatures may reach between 30 to 32 degrees across portions of
West Tennessee near the Tennessee River and middle 30s across much
of the forecast area. Consequently, I`ve issued a Freeze Warning
for some locations near the Tennessee River and continued but
expanded the Frost Advisory to include more of Northeast
Mississippi and include the Memphis area. The evening shift will
continue to monitor trends and adjust hazards as needed if
conditions warrant any changes.

Otherwise, models indicate a ridge of high pressure will remain in
place across the Mid South through Wednesday resulting in mainly
precipitation free weather with highs in the 60s and lows mainly
in the 40s.

Long term models suggest an initial mid-level shortwave trough
will move through portions of the Middle/Lower Mississippi Valleys
late Wednesday night into Thursday and a reinforcing shortwave
trough Friday night into Saturday. Some model run to run
differences remain between the GFS and ECMWF and have kept rain
chances to a minimum until models come into better agreement.

CJC

&&

.AVIATION...
06Z TAFs

Clear skies and light winds to prevail through the period, with
surface high pressure over the Midsouth.

PWB

&&

.MEG WATCHES/WARNINGS/ADVISORIES...
AR...Frost Advisory from 3 AM to 9 AM CDT Monday for Clay-Craighead-
     Crittenden-Cross-Greene-Mississippi-Poinsett-St. Francis.

MO...Frost Advisory from 3 AM to 9 AM CDT Monday for Dunklin-Pemiscot.

MS...Frost Advisory from 3 AM to 9 AM CDT Monday for Alcorn-Benton MS-
     Calhoun-Chickasaw-DeSoto-Itawamba-Lafayette-Lee MS-Marshall-
     Monroe-Pontotoc-Prentiss-Tippah-Tishomingo-Union.

TN...Frost Advisory from 3 AM to 9 AM CDT Monday for Chester-Crockett-
     Dyer-Fayette-Gibson-Hardeman-Hardin-Haywood-Lake-Lauderdale-
     Madison-McNairy-Obion-Shelby-Tipton-Weakley.

     Freeze Warning from 3 AM to 9 AM CDT Monday for Benton TN-
     Carroll-Decatur-Henderson-Henry.

&&

$$



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