Area Forecast Discussion
Issued by NWS Huntsville, AL

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS64 KHUN 242259
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
559 PM CDT TUE MAY 24 2016

.UPDATE...
For 00Z TAFs.

&&

.SYNOPSIS...
(Issued 309 PM CDT TUE MAY 24 2016)

A quasi-Omega pattern is setup over much of North America with
evidence of its gradual demise already showing within water vapor
sat imagery. This pattern is characterized by an upper low off the
CONUS Atlantic coast, ridging over the Midwest/Southeast and upper
low over the Western half of the country. The curious thing about
the Western half of the Omega block is there are several shortwave
troughs within the primary upper low. The sensible impacts to the TN
Valley forecast will be a gradual increase in low-mid levels, warm
daytime high temperatures in the 80s, and increasing chances for
thunderstorms beginning Memorial Day Weekend.

SL.77

&&

.DISCUSSION...
 (Issued 309 PM CDT TUE MAY 24 2016)

The prevailing NW flow aloft on the western flank of the
aforementioned upper low just off the New England coast has brought
a generally subsident environment across the Southeast. An impact of
this subsident, dry environment is the air quality alerts that are in
effect for nearby metro areas of Birmingham, Nashville, and Atlanta.
Will continue to monitor our area in case we need one over the coming
days.

For tonight, expect pleasant, warm conditions to prevail with
overnight lows expected to be a little warmer in the upper 50s to
low 60s. Wednesday`s forecast should be similar to today`s weather
with daytime highs rising into the upper 80s (if not 90). However, as
the upper low continues to move off to the northeast, weakly
amplified shortwaves moving within the subtropical jet edging towards
the TN valley may in fact bring isolated/scattered thunderstorms over
MS/OH river valleys. Though a few of these storms may move close to
the TN valley, anticipating that the dry air over the TN valley will
likely cause these storms to dissipate before arrival. So, the main
impact may be more cloud cover.

The ridge amplifies across the MS/TN river valleys on Thursday and
am slightly increasing daytime highs. With subsident profile
increasing once again on Thursday, have kept a dry, but warm
forecast. However, surface dewpoints will likely be higher given the
movement of the sfc high pressure system eastward over the Atlantic
yielding moisture advection from the Gulf of Mexico/western Atlantic.

As the upper flow pattern continues to shift, several shortwave
troughs over the western half of the country will continue to bring
the possibility of showers and thunderstorms over those areas. In
fact, an additional chance for showers and thunderstorms will be
possible over the Central and Southern Plains into the Ozarks on
Friday. In addition, the movement of the Southeast/OH River Valley
ridge eastward towards the Atlantic (that had been in place on
Thursday) will likely lend towards greater possibility of isolated
afternoon thunderstorms developing over the TN Valley especially over
NW Alabama.

The model depiction of the pattern change for the weekend is rather
chaotic due to what looks to be a tropical/subtropical disturbance
forming just off the Florida Atlantic Coastline underneath the
ridge on Saturday. Meanwhile that Plains shortwave trough will be
moving over the Midwest and Northern Plains effectively up/over the
ridge. The primary impact from the trajectory of that tropical
disturbance (if that model solution verifies) would likely be dry
air inhibiting storm growth. Though the tropical disturbance will
likely not indirectly impact storm growth on Saturday/Sunday,
isolated thunderstorms would still be possible on both days mainly
due to daytime heating. The nature of these storms would tend
towards pulse-like updrafts with quick episodes of rain.

Though higher chances of showers/storms are currently in the
forecast exist on Memorial Day/Tuesday, have included low chance
pops mainly due to aforementioned dry air that would inhibit storm
development.

SL.77

&&

.AVIATION...
For 00Z TAFs: A sfc high covers much of the sern us along with a
weak upper ridge. Convection over AR/MO will dissipate as it tries to
move east tonight. This is due to subsidence across the area and a
fairy dry atmosphere from 7H to the sfc. However will have sct/bkn
ci across the taf sites thru the fcst period. Otherwise vfr
conditions are expected for the next 24 hours for both KMSL and KHSV.

007

&&

.HUN Watches/Warnings/Advisories...
AL...NONE.
TN...NONE.
&&

$$

For more information please visit our website
at weather.gov/huntsville.


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.