Area Forecast Discussion
Issued by NWS Memphis, TN

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FXUS64 KMEG 261115

Area Forecast Discussion
National Weather Service Memphis TN
615 AM CDT Sat May 26 2018


Updated for the 12Z Aviation Discussion


.PREV DISCUSSION... /issued 357 AM CDT Sat May 26 2018/

Relatively benign weather conditions exist across the Mid-South
this morning, although a few showers have developed just west of
the CWA in the past hour or so. A mid-level trough axis extends
southward from the western Great Lakes into the lower Mississippi
Valley with a ridge building over the Southern Rockies.
Subtropical Storm Alberto is taking shape off the Yucatan
Peninsula but won`t really be a player in our forecast until early
next week.

The Memorial Day Weekend will be highlighted by scattered, diurnal
convection similar to what we have seen the past several days.
Weak forcing and moderate instability will support pulse
thunderstorms capable of producing gusty winds and localized
heavy rainfall. Lapse rates from 700-500mb will remain near 6
C/km, limiting the potential for large hail. While scattered
thunderstorms will be possible area wide this weekend, the
greatest coverage is expected to occur along/south of I-40.
Temperatures this weekend will be in the ballpark of
climatological norms with highs in the mid to upper 80s and
overnight lows near 70 degrees.

Subtropical Storm Alberto will begin tracking in a more northerly
direction later today, eventually moving into the Gulf of Mexico
and gradually intensifying into a Tropical Storm (and perhaps a
Hurricane before landfall). Winds across the southeast CONUS will
begin to respond to the approaching Alberto this weekend and early
next week, backing from the east and northeast as the cyclone
tracks north along the AL/MS border before eventually curving off
to the northeast across middle TN. By this time, the ridge will
break down as a northern stream shortwave trough moves across the
upper Midwest. It`s not unusual to see a dry, subsident region
develop on the western side of a tropical cyclone and that MAY
limit convective coverage across portions of the CWA (primarily
northwest) as Alberto approaches.

Should the current forecast track hold, the heaviest rainfall
remain to our east, but we could still see substantial rain
totals across the TN Valley. In total, we`re looking at 1-3 inches
of rain along and east of the Mississippi River with localized
higher amounts possible (mainly over northeast MS). Lighter totals
are anticipated to the west. Wording for heavy rainfall will be
ramped up a notch in the Hazardous Weather Outlook.

The subtropical ridge will begin to rebuild over the Southern
Plains late this week, with the Mid-South settling beneath
northwest flow aloft. In general, PoPs will be lower given
building geopotential heights, but there is a potential for MCS
activity as shortwaves move over the top of the ridge and across
the Ohio Valley. At this time, confidence is low in any
particular solution regarding convection, so will keep PoPs on the
low side and continue to monitor the pattern over the coming
several days. Regardless, we are likely looking at some warm
temperatures toward the end of next week with highs in the low/mid
90s. Will have to keep an eye on heat indices as dewpoints are
expected to remain in the 70s throughout the afternoon.



12Z TAF cycle

Low clouds are currently over portions of northeast Mississippi
but will gradually lift later this morning. Otherwise, VFR
conditions should prevail for much of the forecast period. Some
scattered thunderstorms are currently over portions of east
Arkansas and more showers and thunderstorms are expected to
develop this afternoon and early this evening. Winds will be light
and mainly from the south for much of the forecast period.




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