Area Forecast Discussion
Issued by NWS Mobile, AL
FXUS64 KMOB 270517
Area Forecast Discussion
National Weather Service Mobile AL
1217 AM CDT MON JUN 27 2016
.DISCUSSION...Updated for latest aviation discussion below.
06Z issuance...Isolated TSRA with gusty winds and heavy rain will
impact southeast MS to the west of the KMOB/KBFM terminals through
around 27.06-07Z. VFR should generally prevail overnight, though will
have to watch for some patchy at least MVFR fog for a few hours early
Monday morning, especially near locations where heavy rains fell
Sunday. Additional scattered TSRA, some with strong wind gusts and
reduced visibilities due to heavy rain will impact the area again
Monday. Confidence was high enough to introduce PROB30 at
KMOB/KBFM/KPNS after 27.18Z.
.PREV DISCUSSION... /issued 1008 PM CDT SUN JUN 26 2016/
DISCUSSION...See updated information for land areas below.
UPDATE...Busy evening weather-wise across our area. Scattered
strong to severe storms developed across portions of south central
and southwest AL as well as across a good portion of the northwest
FL Panhandle as a shortwave trough rotating around the eastern
periphery of the upper ridge axis interacted with a highly moist and
unstable environment (2000-3000 J/KG of MLCAPE) and 25-30 knots of
deep layer shear. Earlier convection produced an extensive outflow
boundary which is now pushing into Washington, Mobile and southern
Baldwin counties in southwest AL as of 10 PM. Still rather decent
coverage of convection ongoing behind this feature, with new cells
developing over southeast MS. We updated the forecast to increase
gridded POPs to 30-50 percent over these areas through the remainder
of the evening. Convection is expected to diminish by 1 AM...and will
leave POPs below 20 percent after then for now, but will continue to
monitor trends for further updates. /21
PREV DISCUSSION... /issued 622 PM CDT SUN JUN 26 2016/
DISCUSSION...Updated for latest aviation discussion below.
00Z issuance...VFR conditions will prevail through much of the night
into Monday morning. Sct showers and thunderstorms will develop
during the afternoon Monday with associated reduced visbys and cigs.
PREV DISCUSSION... /issued 326 PM CDT SUN JUN 26 2016/
NEAR TERM /Now Through Monday/...
Upper ridging will continue to weaken and shift westward through
Monday. Meanwhile, a weak front will sink southward across the
Tennessee Valley during the day on Monday. Increasing moisture (PW
values around 2 inches) combined with the weakening upper ridge will
allow for an enhancement in afternoon showers and thunderstorms.
Scattered showers and thunderstorms are expected area wide during
the peak heating hours. Strong instability combined with some
lingering dry air in the sub- cloud layer will create a favorable
environment for gusty winds in the stronger storms. Outside of any
relief from storms, hot and muggy conditions will continue with highs
in the low to mid 90s and heat index values off 100-106. Lows tonight
will fall into the mid 70s inland to upper 70s along the coast. /13
SHORT TERM /Monday night Through Wednesday night/...
A fairly active convective weather pattern is anticipated through
Monday night scattered thunderstorms should continue in the
conditionally unstable airmass overlying the area where layer
precipitable water values average around 2.0 inches. The upper level
ridge that had dominated area weather is carved back to the west.
With the ridge to our west minor shortwave troughs will move across
the area and couple with a surface trough of low pressure overlying
the area...triggering convection.
Convective activity increases as a major shortwave trough moving
down the longwave trough developing over the region drives a frontal
boundary southward across the forecast area. Layer precipitable
water values rise well above normal and approach 2.25 inches.
Thunderstorms and showers are expected to become numerous during the
day. Lack of shear limits the severe risk but could possibly see a
strong outflow boundary with an organized cold pool develop north of
the forecast area where vertical shear is more favorable and then push
south across the area by late afternoon. The greatest threat would be
strong to possibly marginally severe straight line winds. Strong
updrafts are quite possible as afternoon MU CAPE climb to 4000 to
5000 J/kg but large hail remains unlikely as Wet Bulb Zeros remain up
above 14000`. Periods of heavy rainfall are possible and amounts of 1
to 3 inches are possible which could cause some localized nuisance
flooding along poor drainages.
Models have been somewhat inconsistent in whether or nor the front
makes it southward off the coast Tuesday night. With nocturnal
cooling over land giving it a little extra push it`s more likely than
not the weakening boundary moves over the near coastal waters. Due to
some uncertainty...left low end chances for thunderstorms over the
region but bumped them up over the marine area.
Wednesday looks to be another convectively active day as the
boundary shifts north with added push from the sea breeze. Showers
and thunderstorms are expected to become numerous again over our
coastal counties becoming more scattered inland. Precipitable water
amounts remain highest along the coast...around 2.0 inches. Amounts
decrease rapidly moving inland to fairly dry 1 to 1.25 inches over
our more inland counties. Activity is expected to taper off overnight
with the chances for showers or thunderstorms basically being
confined to areas near the coast and over the Gulf waters.
Temperatures should be held in check with the increased convective
activity expected to occur across the area...average daily
temperatures should trend near to a little cooler than
climatological norms through the period. /08
LONG TERM /Thursday Through Sunday/...
Drier conditions are expected from Thursday through Sunday. An upper
level longwave trough remains anchored over the Eastern States with
the forecast area remaining generally west of its axis. This will
provide for a much drier airmass then we experienced earlier in the
week. Layer precipitable water amounts will trend below to near
normal for this time of year. And a generally diurnally driven wind
and convective pattern develops over the area. Winds onshore during
the day...offshore at night. Pop up showers generally developing over
land during the day and then over the Gulf at night. The GFS does
start increasing layer precipitable water amounts by Saturday night
and pushes a frontal boundary near the northern portion of the
forecast area Sunday. Too much uncertainty to completely buy off on
this solution at the moment but have kept high chance PoPs in the
forecast for now on Sunday. Daily average temperatures are expected
to trend near to a little warmer than average Thursday through Sunday.
High pressure will remain in place across the marine area
through the week. This will maintain a generally light onshore flow
during the day, with a slight enhancement due to the seabreeze. Seas
will remain 1-2 feet. /13
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