Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Mobile Alabama
953 PM CST Wednesday Dec 17 2014

Update...infrared satellite imagery shows high level cloud cover
increasing across the forecast area late this evening...and we have
increased the sky coverage through the overnight period. We left the
overnight minimum temperature forecast alone for the most part at this point
given the increased cloud coverage. All other elements are on track. /21


Previous discussion... /issued 530 PM CST Wednesday Dec 17 2014/

18.00z terminal forecast discussion...
VFR conditions will continue through the next 24 hours underneath
scattered to occasionally broken middle and high level cloud cover. Calm
to light north to northeast winds will prevail into Thursday
afternoon. /21

Previous discussion... /issued 328 PM CST Wednesday Dec 17 2014/

Short term [tonight through Thursday afternoon]...surface high
pressure will continue to ridge south from the northern plains and
Great Lakes into the southeast states through Thursday. A shortwave
currently over The Four Corners will move east into the Southern
Plains/Ozarks by early Thursday morning. Southwest upper level flow
on the south side of this system will bring periods of high
cloudiness into the forecast region through the course of the night.
Light winds...low dewpoints...and very dry soil conditions will
favor strong radiational cooling. The extent of the high clouds will
ultimately determine how cold it will get tonight. Forecast lows are
slightly cooler than the mav (the mav has not done well recently
with low temperatures due to the dry soils)...but did not go quite as low
as the met due to the cloud cover. This yields lows in generally in
the upper 30s to around 40. If the high clouds stay thin
enough...then it will likely be a few degrees colder.

The aforementioned shortwave shears out as it moves east into the
Ohio Valley on Thursday. An area of light rain that develops tonight
west of the MS river will weaken as it moves east toward the area
Thursday afternoon as all deep layer forcing is lost. Only a slight
chance of very light rain across mainly Choctaw County late Thursday
afternoon. Otherwise...conditions remain dry with just a further
increase in cloud cover. Highs generally in the low to middle
60s...with some upper 50s north of Waynesboro/Butler. 34/jfb

[thursday night through friday]...a medium amplified upper level
shortwave over The Rockies Thursday night will move eastward over
the Central Plains on Friday...and then over the Mississippi River
valley Friday night. An area of surface low pressure will form over
the extreme northeast portion of the Gulf of Mexico and move east
along the northern Gulf Coast...reaching the Mississippi Sound by
late Friday night. Large surface high pressure across the eastern
Continental U.S. Will lift northeast and maintain a light northeasterly to
easterly wind flow across the forecast area. While a warm front
associated with the approaching surface low is expected to remain
over the north central Gulf waters or push slightly inland from the
beaches Friday night.

Cloud coverage and rain chances will continue to increase Thursday
night and Friday as precipitable water values increase to between
1.25 to 1.5 inches. Expect isolated to scattered precipitation west of the
Alabama River Thursday night...followed by scattered to numerous
coverage during the day Friday across the entire forecast area. The
best chance of rain will occur Friday night as the system approaches
from the west...with likely to definite rain chances. Instability and
shear remain low at this time...but depending on the eventual track
of the system...some strong storms may be possible along the
immediate coast. Rainfall amounts will range from around one-half
inch near Destin to 1.5 inches across inland southeast Mississippi.

Lows Thursday night will fall into the low to middle 40s inland
areas...with upper 40s to lower 50s along the immediate coastal
sections. Highs on Friday will range from 54 to 59 degrees. Lows
Friday night will range between 34 and 39 degrees inland areas...and
from 40 to 45 degrees along the immediate coastal sections. /22

Long term [saturday through wednesday]...the surface low moves
across the coastal portion of the forecast area on Saturday and
looks to have a dry slot impacting the will have chance
to good chance probability of precipitation for most of the area on Saturday then dry
conditions follow for Saturday night. May see a continuing
potential for some strong storms early Saturday over the eastern
coastal portion of the area. An upper trough meanwhile amplifies over
the central states through Sunday and continues to strengthen
through Tuesday into a longwave trough while beginning to advance into
the eastern states late in the period. With a southwest flow aloft
over the area and a series of shortwaves moving across the
region...expect to see a series of surface lows track eastward
across the northern Gulf through Monday followed by a cold frontal
passage Tuesday night. This pattern supports small probability of precipitation returning
to the southern portion of the area Sunday night which gradually
increase to chance probability of precipitation across the area by Tuesday. There is the
potential for a vigorous surface low to develop on the cold frontal
boundary as the front advances to near the area which could portend
strong storms for Tuesday...but this is well into the extended
period and will monitor for now. /29

17.18z kmob/kbfm and kpns taf cycle
VFR conditions will persist through the next 24 hours. 34/jfb

Marine...a surface ridge to the north of the area will maintain a
light northeast flow tonight...becoming more easterly on Thursday.
Winds increase out of the east on Friday and veer to the southeast
and south Friday afternoon into Friday night ahead of a developing low
pressure system off the Texas coast. The low tracks along the coast of
Alabama/northwest Florida late Friday night into early Saturday...and some strong
storms with gusty winds are possible especially over the open Gulf
waters. A light to moderate offshore flow is expected in the wake of
the system over the weekend. Winds become southerly on Monday and
gradually increase Monday night ahead of the next developing storm
system. Seas build to around 4 feet Friday/Friday night...but diminish back
to 1-2 feet by late Saturday night into Sunday. 34/jfb


Preliminary point temps/pops...
Mobile 39 65 47 63 55 / 00 10 20 60 70
Pensacola 42 64 49 63 58 / 00 05 05 50 70
Destin 44 63 49 64 59 / 00 05 05 40 50
Evergreen 36 62 41 61 49 / 00 05 05 60 80
Waynesboro 37 60 42 58 44 / 00 10 30 70 80
Camden 36 61 40 56 45 / 00 10 05 70 80
Crestview 35 65 43 64 52 / 00 05 05 40 60


Mob watches/warnings/advisories...


National Weather Service Glossary of Abbreviations