Scientific Forecaster Discussion
fxus64 kbmx 221737
Area forecast discussion
National Weather Service Birmingham Alabama
1237 PM CDT sun Sep 22 2019
for 18z aviation.
/updated at 0318 am CDT sun Sep 22 2019/
One more day of easterly flow for the area, as high pressure begins
to move east and elongate off the East Coast. The easterly component
will keep temperatures in the upper 80s to low 90s, with just some
fair weather cumulus lat morning through the afternoon. Once the sun
sets, winds calm and we drop into the 60s to near 70.
/updated at 0318 am CDT sun Sep 22 2019/
Monday through Saturday.
A shortwave trough will move from the Great Lakes to New England
along Monday, allowing the subtropical ridge to flatten somewhat
over northern Alabama with mid-level flow becoming northwesterly. This
will allow a cold front to move towards the Tennessee Valley by
afternoon. A narrow moist axis of tropical origins will be
advected in from the west right along/ahead of the front, with
pwats around 2 inches. On the other hand, forcing will be weak
with warm temperatures aloft. Thus instability will be limited
with weak mid-level lapse rates, keeping any thunder potential
isolated. Scattered showers will be be possible in our far
northwest counties by late afternoon. Given the somewhat moist air
mass, coverage could over-perform in our far northwest counties,
but rainfall amounts should be light given the limited
instability. Activity should weaken with the loss of daytime
heating as it approaches the I-59 corridor around sunset and
encounters greater inhibition. Elsewhere, rain-free conditions
will continue with pre-frontal westerly flow causing temperatures
to warm well into the lower 90s.
Westerly flow will be present Tuesday/Wednesday between flat
ridging over the Gulf and an amplifying trough over the northern
plains, while a cutoff low spins over Arizona and the northern
baja. The front will begin to stall out somewhere over our far
southern counties Tuesday afternoon, though models disagree
regarding how far south it will make it. The front and associated
moist axis will serve as a potential focus for showers/storms,
but ridging and warm temperatures aloft will limit coverage to
either isolated or widely scattered across our southern counties.
Highs will be at least a couple degrees cooler across our
northern counties. Lows Tuesday night should reach the 50s in our
typically cooler northeastern counties. The front will begin to
lift back to the northeast on Wednesday in response to a surface
low over Ontario, with just enough moisture for an isolated
shower/storm to be possible in West Alabama. Highs will be in the
low to mid 90s.
A cold front will stall out well to our north on Thursday as
ridging strengthens over Florida and the cutoff low lifts towards
The Four Corners. There could be just enough moisture for an
isolated shower/storm in our northeast counties but chances appear
to be only 10 percent or less at this time. The warming trend will
continue. An amplified western trough/eastern ridge pattern is
still on track to set up for next weekend, aided by a blocking
ridge over the North Pacific and a developing Rex block over the
North Atlantic. Nearby anomalous 596 decameter ridge will result
in highs in the mid to upper 90s. Recent dry conditions, and 500mb
heights and 850/925mb temps ranging from the 99th percentile to
the climatological maxima per the European model (ecmwf) ensemble situational
awareness table support record highs, keeping in mind that our
record highs have begun their climatological descent.
18z taf discussion.
VFR conds thru the period with no cig or vsby issues. Fair weather
cumulus will persist thru 00z, then erode by 01z. Sfc winds will
be in the 4-6 kt range this afternoon, but a weak gradient will
result in vrbl directions. A cool front will move into northwest
by 15z and sfc winds will become west-southwest after 15z ahead of
the boundary. Weak forcing with the front, along with the
presence of dry air aloft, will cause the pre-frontal showers to
weaken and not likely have any impact on northern taf sites.
Dry and warm conditions continue today. The next chance of rain
comes Monday, but with only isolated to scattered coverage across
northwestern areas. Afternoon relative humidity values are
expected to remain above 30 percent each afternoon today and
Monday, potentially reaching 30 percent in northern portions of
central Alabama Tuesday afternoon. Kbdi values will remain
elevated as drought conditions persist.
Preliminary point temps/pops...
Gadsden 60 92 66 89 57 / 0 10 10 10 0
Anniston 62 92 68 90 59 / 0 0 10 10 0
Birmingham 66 93 70 91 62 / 0 10 10 10 0
Tuscaloosa 66 92 70 91 64 / 0 10 10 10 10
Calera 63 93 70 91 62 / 0 0 10 10 0
Auburn 64 90 69 90 64 / 0 0 10 20 10
Montgomery 63 93 70 94 66 / 0 0 0 20 10
Troy 63 93 67 93 65 / 0 0 0 20 10