May 20, 2013
NEAR TERM [Through Tonight]...
The large scale longwave split flow pattern is highlighted by a Rex
block out west, a positively tilted trough from eastern Canada swwd to
a closed low and ewd moving shortwave over New Mexico, and a ridge
over the Caribbean. Water vapor imagery continues to show
persistent moisture plume feeding newd between the trough and
ridge which includes the NE Gulf region. Into tonight, the low
will move newd across TX panhandle into ern ks. This will allow
trough to continue to pivot ewd with Gulf moisture plume sagging
further sewd. At surface, a stalled front was draped across the NRN
FL Peninsula stretching sw across the Gulf of Mexico to low
pressure in the Bay of Campeche.
Regional radars indicate a shield of mainly light rain, associated
with post frontal wave, extended from the Ern Gulf newd into the
Carolinas. The back end of this rain shield will move nw-se across
local area this evening and exit the SE Big Bend before sunrise.
In its wake, noticeably cooler and drier air will move in with low
rain chances or more likely drizzle and sprinkles focused on the
FL Big Bend zones mainly until midnight. So 0-40% mainly eve NW-SE
PoP gradient. Latest obs show that cooler air/declining clouds
moving faster than earlier anticipated. Mid-Aftn temps along MS/AL
border already in upper 30s. This is reflected in latest GFS/NAM and
adjusted MET which all came in around 2 degrees cooler Wrn third,
3 degrees cooler Cntrl third and 5 degrees cooler Ern third of
CWA than 00Z run. However, WRF, MOS guidance, ARW4, and adjusted
MET all came in at or slightly higher than previous run. Will
tweak down inherited temps a degree or two most sites. New min
temps justify a light freeze warning 4-9 AM tonight into early
Friday for Nrn portions of SE AL and the Nrn tier GA counties.
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