Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Mobile Alabama
1140 PM CDT Sat may 23 2015
24.06z issuance...VFR conditions will prevail through
Sunday morning. Lower clouds bases will develop through the late
morning on Sunday as moisture levels increase. Chances for scattered
showers and thunderstorms will also increase with thunderstorms in the vicinity expected at
all terminals by early afternoon. Southerly winds around 10 knots
tonight will increase to around 15 knots Sunday afternoon. /13
Previous discussion... /issued 401 PM CDT Sat may 23 2015/
Short term...(tonight through Monday night)..for tonight through
Sunday...a surface ridge of high pressure
continues to extend from the western Atlantic Ocean and eastern
Seaboard to the eastern Gulf of Mexico this afternoon...while an
upper level ridge of high pressure meanwhile stretches from the
eastern Gulf to the western Atlantic. Subsidence associated with
high pressure has surpressed convective development across the
region this afternoon...though visible satellite imagery has shown
some cumulus which has attempted to tower along the seabreeze though
with not much Luck. Surface observations indicate that temperatures
have warmed into the middle 80s to around 90 across the forecast area
this afternoon. Dewpoints were much lower over interior areas to the
north of the seabreeze...generally in the upper 50s to lower 60s...
while low level moisture was increasing south of the seabreeze with
dewpoints rising into the middle 60s to around 70.
Surface high pressure will continue to remain oriented from the
western Atlantic/eastern Seaboard through the eastern Gulf tonight
before moving slowly eastward during the day Sunday. Upper level
ridging will also continue to remain intact over its current
position overnight before also slowly progressing eastward Sunday.
Southwest flow aloft is expected to increase across our forecast
area during the day Sunday as the ridge axis moves east and as a
deep upper level trough over the Rocky Mountains region slowly moves
eastward. Little change to the overall forecast reasoning tonight.
Winds become light easterly over inland areas tonight...and upper
ridge should suppress convection through the evening. A few of the
short range/hi-res models have shown potential for development of
isolated showers near the immediate coast and the offshore marine
zones late tonight into early Sunday morning along narrow axis of
moisture along weak coastal boundary and increasing southwest upper
flow. We will keep a slight chance of convection over the coastal
zones and adjacent marine zones after midnight. Convection should
become more scattered in coverage across much of the County warning forecast area during the
day Sunday underneath more pronounced southwest upper low and
increasing boundary layer moisture/precipitable water values between
1.5 and 1.7 inches. A few of the typical stronger afternoon
storms could produce brief strong and gusty winds...frequent
lightning and heavy rainfall. An isolated/brief marginally
severe storm cannot be ruled out given afternoon MLCAPE values
approaching 1500 j/kg. Lows tonight will range from the middle to upper
60s inland to the lower 70s near the coast. Highs Sunday will range
from the middle 80s to around 90. /21
Sunday night through Monday night...the energy from a disorganizing
upper system over the Desert Southwest moves northeast across the
plains...pushing an upper ridge over the eastern Continental U.S. Eastward.
This allows the energy to affect more of the lower miss River Valley
and southeastern Continental U.S.. with the shifting of the upper ridge and the
added upper energy passing over/near the forecast area...the chance of rain GOES
up for this period of the forecast. The best chance is expected to be
over northwestern portions of the forecast area...closer to the passing energy.
With the higher probability of precipitation comes a smaller diurnal temperature range...mainly for
northwestern portions of the forecast area.
Looking at the chance of strong to severe...with abundant daytime
heating expected mainly over the eastern half of the
forecast area...thunderstorms could become strong to severe. Wind-shear is
limited and unidirectional...so am not expecting supercells.
Basically looks like the usual pulse severe scenario...with strong
winds and hail the primary threats for any storm that does become
strong to severe.
Long term...(tuesday on)...Tuesday through Wednesday night...the
last of the energy from the southwestern system moves northeast over
the miss River Valley to over the Great Lakes...lessening it affect
on the chance of rain over the forecast area. It does weaken the surface ridge
stretching west over the southeastern states...and the more organized
onshore flow over the lower miss River Valley and southeastern Continental U.S..
with the slow decrease in the chance of rain...but the upper ridge
shifting east...temperatures moderate upward a bit. Overnight lows remain a
bit above seasonal...with daytime highs around.
Thursday through Saturday...more upper energy moves southeast over
the western Continental U.S....then begins to meander eastward over the southern
US rockies and Central Plains. The upper ridge that has shifted to
off the East Coast remains pretty much where it is. The energy as it
is. The surface ridge stretching west over the southeastern Continental U.S.
Remains pretty much as is...in a weakened...but present state. Temperatures
a bit above seasonal...with isolated afternoon/evening thunderstorms and rain.
23.18z terminal forecast discussion...
a VFR forecast are forecast to prevail through the next 24 hours.
Scattered cumulus decks with bases of 5-6 kft above ground level will persist this
afternoon along with higher cloud decks. Fog potential remains low
tonight though brief MVFR visible reductions cannot be entirely ruled
out over a few locations. Lower level cloud decks...possibly MVFR
could develop Sunday morning...but confidence was low enough to keep
out of taf/S at this time. /21
Marine...a ridge of high pressure will build from the western
Atlantic to the north central Gulf through early next week.
Southeasterly winds will continue to increase over the marine area
this afternoon and evening...with moderate to occasionally strong
southeast flow prevailing into Tuesday. Small craft should exercise
caution late tonight through Tuesday as wind speeds increase to the
15-20 knot range offshore and near local bays/sounds. Seas will
increase to 4-6 feet well offshore Sunday through Tuesday. /21
Preliminary point temps/pops...
Mobile 70 88 70 85 71 / 20 40 30 60 50
Pensacola 73 87 73 86 74 / 20 40 30 40 50
Destin 74 86 75 85 75 / 20 30 20 50 50
Evergreen 66 87 70 88 68 / 10 30 30 30 60
Waynesboro 66 86 70 81 68 / 10 40 50 60 60
Camden 66 87 70 88 67 / 10 30 30 40 60
Crestview 67 90 68 89 70 / 20 30 30 40 60
Alabama...high rip current risk from Sunday morning through Tuesday
afternoon for lower Baldwin-lower Mobile.
Florida...high rip current risk from Sunday morning through Tuesday
afternoon for coastal Escambia-coastal Okaloosa-coastal