Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 201436 AAB

Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
836 AM CST Mon Nov 20 2017

.DISCUSSION...See updated information for land areas below.


.UPDATE...Have updated for the expiration of the Freeze Warning.
No other major changes. /29


.PREV DISCUSSION... /issued 531 AM CST Mon Nov 20 2017/

DISCUSSION...Updated for latest aviation discussion below.

12Z issuance...VFR CIGs/VISBYs expected through the day as surface
high pressure passes north of the area, with a winds shift from
northeast to east the only real change. Tonight, the development
of a surface trough over the northeast Gulf will bringing
increasing mid level cloud over the area along and southeast of
I65, but am not expecting this to impact operations, with CIGs
remaining well above MVFR levels.


PREV DISCUSSION... /issued 452 AM CST Mon Nov 20 2017/

NEAR TERM /Now Through Monday night/...A shortwave system moves from
over Tx eastward over the northern Gulf before ultimately ending
up over the north-central Gulf coast by Tuesday morn. This system
along with another, stronger system moving east over the
US/Canadian border, pushes a surface high from over the
Mississippi River eastward, to off the the Carolina coast. This
surface high gets a squeeze in the process, leaving a surface
ridge stretching west over the eastern Conus and bring a general
easterly flow over the forecast area, especially coastal waters.
As the Tx system moves over the Gulf later today and tonight, it
begins to develop a surface trough over the northeastern Gulf
tonight and with that, clouds spread north over areas along and
southeast of I65. Rain starts to spread north over along the
eastern boundary of the forecast area. Coastal areas of the
western Florida panhandle may see some light shra, but am not
anticipating much inland penetration before sunrise. With the loss
of cool northerly push along with abundant heating from the sun
today, some areas see temps moderating upward (areas north of
Highway 84) whilst the rest of the forecast area see highs around
the same as yesterday. Highs ranging from around 60 to 65 expected
today. Tonight sees the greatest rebound, especially areas
southeast of I65 as increasing clouds decrease overnight cooling.
Lows ranging from upper 30s northwest to upper 40s southeast. /16

SHORT TERM /Tuesday Through Wednesday night/...An upper level
trough amplifies across the eastern half of the CONUS and Gulf of
Mexico, while upper level ridging persists across the western
portion of the CONUS through mid-week. This pattern opens the door
for several shortwaves to spill into the region during the short

Surface high pressure quickly departs the region early Tuesday and
is pushed into the western Atlantic. A surface low in southern
Canada associated with the aforementioned deep upper level trough
will swing a weak cold front down through the Plains and Mississippi
River Valley region Tuesday and Tuesday night. Meanwhile, a surface
low develops over the northeastern Gulf during this timeframe (well
south and east of our marine area). The departing high and formation
of a low over the Gulf allow moisture to briefly return across the
area on Tuesday, especially across the southern and eastern portion
of the area. Temperatures will respond to the increase in moisture
and will rise into the mid to upper 60s with a few spots hitting 70
on Tuesday. Isolated to scattered rain showers cannot be ruled out
Tuesday and Tuesday night due to wrap-around precipitation from the
surface low over the Gulf. Any rain that does occur will generally
be east of I-65 with the bulk of the rain staying well east of our
area. Lows by Tuesday night will dip into the mid to low 40s west of
I-65 with upper 40s and low 50s east of I-65.

In the wake of the first shortwave and weak cold front, drier air
spills into our northwestern counties once again during the day on
Wednesday. There remains an outside chance of isolated showers
across the Florida panhandle and south central Alabama again on
Wednesday, but the remainder of the area will stay dry. This
moisture contrast will be reflected in the temperatures on Wednesday
as the northwestern portion of the local area stays dry and thus
will remain on the cooler side. Conversely, daytime temperatures
across the southeastern half of the area will rise into the upper
60s in response to the moisture. By Wednesday evening, temperatures
will dip into the 30s west of I-65, while only falling into the mid
to low 40s east of I-65. 07/MB

LONG TERM /Thursday Through Sunday/...The upper level trough
across the eastern half of the CONUS will slowly shift east toward
the western Atlantic through the weekend. As this occurs, the upper
level ridge across the western half of the CONUS begins to meander
east toward the region late in the weekend and early next week.

Despite several more shortwaves moving through the trough, the
location of the trough (with respect to the local area) will keep
northerly flow into the region through the end of the work week.
This will continue to usher drier air into the local area and will
keep the forecast dry. High pressure builds back into the central
part of the CONUS mid-week and spreads east into the Deep South late
in the week. Another surface low develops and quickly dives across
southern Canada on Friday, which may drop yet another weak front
through the region later the weekend. However, there does not appear
to be much moisture return ahead of the front, thus will continue
a dry forecast through the weekend.

Thanksgiving will be cool with highs in the upper 50s west of I-65
with temperatures topping out in the mid to low 60s further east.
Saturday should be the warmest day as highs will top out in the
upper 60s and low 70s. Lows will fall into the 30s and 40s inland
each night with slightly warmer temperatures at the beaches. 07/MB

MARINE...Surface high pressure shifts east to off the Carolina
coast, leaving a surface ridge over the eastern Conus. This shifts
winds from northeast to east, decreasing with the shift. As a Tx
upper system moves over the Gulf, a surface trough develops over
the northeastern Gulf, returning winds back to northerly, but
leaving them on the lighter side. More upper energy digging
southeast over the Plains begins to develop a surface low over the
eastern Gulf Wednesday night, strengthening the offshore flow
over area coastal waters in the process. Winds settle into the
weekend, but remain offshore as surface high pressure moves over
the Plains, then stalls. /16




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