Area Forecast Discussion
Issued by NWS Memphis, TN
FXUS64 KMEG 261755 AAA
Area Forecast Discussion...UPDATED
National Weather Service Memphis TN
1155 AM CST Sun Feb 26 2017
Updated for 18Z Aviation Forecast Discussion below.
.PREV DISCUSSION... /issued 1027 AM CST Sun Feb 26 2017/
At 10AM, temperatures have warmed quickly from the 20s and into
the mid to upper 40s in this arctic airmass. As a result, relative
humidity values have already dropped into the lower 30s along and
east of the Mississippi River. Although moisture return will
occur west of the Mississippi River, eastern areas will not see
much recovery with southeast winds. Went ahead and issued a fire
weather notification message for the eastern half of the forecast
area due to dry vegetation and very dry air in place.
Also went ahead and bumped temperatures up a couple of degrees
across the southern and eastern parts of the forecast area. All
other weather parameters are on track. New zones and grids are now
PREV DISCUSSION... /issued 524 AM CST Sun Feb 26 2017/
Updated for the 12Z Aviation Discussion
PREV DISCUSSION... /issued 357 AM CST Sun Feb 26 2017/
The surface anticyclone has settled over the Mid-South early this
morning, resulting in light and variable winds. Temperatures have
dropped into the mid 20s and lower 30s across the CWA and will
fall a few more degrees before sunrise. Quasi-zonal flow aloft
will highlight the synoptic pattern today, gradually becoming a
bit more southwesterly early next week. Southeast winds will
resume at around 10 mph today as the surface high moves east.
Moisture will increase with time as southerly flow persists,
resulting in warmer overnight lows and fueling the upcoming rain
chances. Temperatures will be warmer across the region this
afternoon, with highs generally in the mid 50s to near 60 degrees.
Dry weather is expected across the forecast area through this
afternoon, but rain chances will ramp up quickly during the
evening and overnight hours.
A complex of showers, and possibly a few thunderstorms, is
expected to affect the area Sunday night and Monday. The greatest
rain chances on Monday will occur before noon, as the primary
forcing slides east with the departing shortwave trough. Much of
the area may be dry Monday afternoon. Temperatures will top out in
the upper 50s to mid 60s but skies will remain mostly cloudy.
We`ll see another uptick in rain chances Monday night as the a
more subtle shortwave trough interacts with an intensifying low-
level jet. That said, coverage should be limited enough to only
warrant chance PoPs at this time. Monday night lows are expected
to remain in the 50s.
Models continue to indicate an abundance of cloud cover across the
region on Tuesday. Both the GFS/NAM MOS temperatures look a bit
overdone given the anticipated cloud cover. Forecast highs were
kept in the mid/upper 70s across the CWA, which are still near
record values at several sites. Continued moisture advection on
Tuesday will help push dewpoints into the mid 60s. A surface low
moving into the Midwest will drag a cold front through the Central
Plains on Tuesday.
Strong surface instability (by late February standards) and
significant deep-layer shear will promote the development of
organized thunderstorms in the warm sector of the aforementioned
cyclone Tuesday afternoon. While storms may eventually grow
upscale in mode, storms could be more discrete earlier in the
period. In the end, it could be a messy, complex convective
setup. Here`s the main message: Strong to severe thunderstorms
will be possible Tuesday afternoon, continuing through the
overnight hours into the day on Wednesday. The primary hazard
will depend heavily on storm mode, so the details are still
unclear at this point.
The cold front will move across the Mid-South on Wednesday. The
severe threat will continue along and east of the surface
boundary, which is currently forecast to be near the Mississippi
River by midday. Rain chances will linger into Wednesday night,
but cooler and drier air will advect into the area in the wake of
the cold front. Dry weather is anticipated Thursday through at
least Saturday as quasi-zonal flow aloft resumes over much of the
CONUS. Temperatures will be near climatology Thursday and Friday
(lows in the 30s and highs in the mid/upper 50s) but should begin
to climb by Saturday.
The GFS, ECMWF, and GEM all indicate a trough approaching from the
west late in the period. However, differences in timing and
strength of the trough currently exist, resulting in little
confidence in any particular solution.
VFR to prevail through the late evening, as increased moisture
in the FL050 to FL100 layer arrives from the southwest,
overspreading an initially dry layer below.
Primary forecast concern is timing and position of a marine warm
front overnight. NAM model depicts a shallow marine layer surging
north into the north MS toward 12Z, ahead of a midlevel disturbance.
TSRA will be possible along and north of the advancing surface
warm front. This would provide MEM and outside chance of thunder
between 08Z and 10Z, based on projected warm front placement and
midlevel disturbance timing. Further north near JBR, reinforcing
cooler air should provide better chances for LIFR toward 12Z. TUP
will see most persistent TS chances into the daylight morning
hours, until the convectively-enhanced midlevel disturbance