Area Forecast Discussion
Issued by NWS Huntsville, AL
FXUS64 KHUN 241113 AAA
Area Forecast Discussion...UPDATED
National Weather Service Huntsville AL
613 AM CDT WED AUG 24 2016
For 12Z TAFs.
(Issued 341 AM CDT WED AUG 24 2016)
Across the greater North American domain, a troughing-west and
ridging-east large scale pattern continues in the mid and upper
levels of the troposphere. Within a busy northern stream/polar jet,
a vigorous upper level system moving eastward just north of the
US/Canada border should weaken as it heads to north of the Great
Lake to SE Canada. It will be joined by a disturbance moving to the
northeast across the central Front Range. South of the Polar jet,
strong upper level ridging in the 597 decameter height range was in
place across the northern Gulf, bringing a light northerly flow over
this region. Otherwise, mostly clear skies ruled across the area
this morning, with overnight lows into the upper 60s to lower 70s.
Today, with less clouds, very warm to hot conditions are in the
forecast this afternoon. A light southeast to south surface flow
will continue a feed of moisture to the region. This moisture and
passing upper level systems should lead to isolated shower and
thunderstorm formation, mainly this afternoon. A look at forecast
soundings suggests the usual gusty winds to 40 mph and brief
downpours with the more substantial showers. Any showers that form
should quickly fade late in the afternoon/early evening with a loss
of daytime heating. A similar forecast is expected on Thursday, with
a slight chance of mainly afternoon convection.
Daily high temperatures into the lower 90s is generally expected for
most of this forecast period. This warmth along with dewpoints
rising into the low, and at times mid 70s degrees will yield heat
indices ranging from the mid/upper 90s our eastern areas, and to the
100-105 range over NW Alabama. Thursday afternoon will be the
hottest day, with the higher heat index values. Areal coverage of
the 105 degree area per grids looks too small for heat advisory
considerations at this time. Even so, usual summer time precautions
for heat are in order.
The above noted southern Canadian low as it moves east will bring a
cold front towards the region late this week. Yesterday, looked like
it would pass across the area during Friday; now it appears it will
be a close call per the GFS/ECMWF. In any case, the proximity of
this boundary will lead to somewhat higher rain chances on Friday.
The focus now switches to the tropics, and what will become of a
disturbance nearing the Leeward Islands of the NE Caribbean.
Tropical track forecasts from 00Z are in remarkably good agreement
moving it just north of the Virgin Islands, Puerto Rico, Hispanola,
and across the Bahamas through Saturday. Afterward, low confidence
on what will become track and strength of this system. The ECMWF
had been the most consistent run-to-run with this system till this
morning`s run --- moving its landfalling location from southern
Alabama to western Lousiana. The GFS on the other hand has been
maintaining a more northward track along the east coast of Florida.
Given tropical system are hard to forecast this far out, what comes
from this system will greatly affect our sensible forecast early
next week. This go around stayed close to continuity and a slight
chance of showers/t-storms on Mon.
For 12Z TAFs: With a fairly strong ridge of high pressure in place
from the mid Atlantic Basin into the lower SE states, VFR conds are
generally xpcted through the TAF period. Mid/high clouds are again
xpcted across the area later today, with sfc winds veering toward the
s near 5kt.
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