Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 270441 AAC

Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
1141 PM CDT MON SEP 26 2016

.DISCUSSION...Updated for latest aviation discussion below.


06Z issuance...Frontal zone has eased into the far northwest zones.
East of the boundary, there are indications that low cigs and fog
will be developing overnight mostly over the interior. Vsby could be
reduced to IFR/LIFR levels at times. Winds light to calm. /10


.PREV DISCUSSION... /issued 958 PM CDT MON SEP 26 2016/

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

UPDATE...Weather maps this evening shows a deeply reflected low
pressure system (surface and aloft positioned) over southern Ontario
Canada to the upper Mid-West. Extending out from this large scale
synoptic scale low, a frontal zone was draped from the Ohio River
Valley to northern Al/northern LA back across eastern TX. East of
this boundary, an upper level low pressure system that has been in
place over the southeast the past few days is filling and will be
absorbed as lower heights aloft at the base of the larger long wave
trof move in from the northwest. Still seeing some lingering shower
activity over the northwest zones.

With the close proximity of the front, most notable change comes
with the potential for late night low clouds and fog development. The
high resolution NMM and NAM12 indicates that areas of fog are favored
overnight, reducing visibility to less than 3 miles mainly along and
north of I-10. Short range ensembles show increased percentages of
fog in the same areas. Considering this, forecasters have made an
update to gridded weather indicating fog development late. /10

PREV DISCUSSION... /issued 628 PM CDT MON SEP 26 2016/

DISCUSSION...Updated for latest aviation discussion below.

00Z issuance...Bulk of afternoon convection that has been slipping
generally southward across the forecast area has shown a decreasing
trend in areal coverage to start off the evening forecast. Will
maintain a vcty of shra thru 27.03z for MOB/BFM given latest radar
trends. Left over cigs are forecast to remain at mid and high levels
thru 27.06Z. Could see some LIFR/IFR cigs as a result of patchy late
night br development in some areas mainly after 27.09Z, especially in
areas that received afternoon rain. Wind light to calm. /10

PREV DISCUSSION... /issued 404 PM CDT MON SEP 26 2016/

NEAR TERM /Now Through Tuesday/...Scattered showers and thunderstorms
continue to develop over the much of the forecast area this
afternoon with heavy rainfall and frequent cloud to ground lightning
being the main threats so far today. As a result have had to issue a
few flood advisories for lower parts of Baldwin county in Al and
Escambia county in NWFL with the latest advisory valid until 5 pm.
For the remainder of today expect more scattered showers and
thunderstorms to develop over most locations in the forecast area
with the best coverage occurring generally along and south of the I-
10 corridor through early this evening. With limited instability and
forcing compared to the last couple of days believe the main threat
with the heavier showers or thunderstorms will be heavy rainfall
rates possible up to 2 inches per hour along with frequent cloud to
ground lightning. Gusty winds mostly below 40 mph will also be
possible with the some of the stronger thunderstorms by late
afternoon. For late tonight and most of Tue morning expect mostly
clear skies with some patchy fog reducing visibilities to 2 to 4
miles mainly around sunrise. By late Tues a broad upper trof over
the upper plains and great lakes will begin to dig south late in the
day allowing slightly better forcing in the mid levels to eventually
shift southward late in the day. With this expect more scattered
showers and thunderstorms to develop over most locations in the
forecast area with the best coverage occurring over the western and
norther parts of the forecast late in the day for now. With the
slightly better forcing in the mid levels late in the day combined
with slightly higher surface based instability a few stronger
thunderstorms will be possible over inland areas late in the day.
Gusty straight line winds...frequent cloud to ground and heavy
rainfall will be the main threats with the stronger storms. 32/ee

As for temps will start with the blended guidance and adjust closer
to the current mav guidance mostly due to persistence and better
consistency with surrounding wfos. Lows tonight will range from the
upper 60s for most inland areas and the lower to middle 70s along
the immediate coast. Highs tue will climb to the upper 80s to near
90 inland and the mid to upper 80s near the coast. 32/ee

SHORT TERM /Tuesday night Through Thursday night/...A massive upper
low over the Great Lakes region and interior northeast states shifts
southward through Wednesday night, dominating the eastern states through
Thursday night. A frontal boundary will be draped across the forecast
area Tuesday evening, and slowly shifts southward into the northern
Gulf on Wednesday while a reinforcing cold front approaches from the
north. The reinforcing cold front moves through the forecast area on
Thursday and ushers cooler air into the region. Precipitable water
values drop off precipitously (sorry) from near 1.5 inches Tuesday
evening to around 0.5 inches by Wednesday evening as the deep layer
northerly flow ushers in drier air, with similar values persisting
through Thursday night. With the movement of the front and drier air
shifting into the area, will have slight chance pops for much of the
area Tuesday night and slight chance pops near the coast Wednesday
morning, followed by dry conditions for the remainder of the period.
Lows Tuesday night range from the lower/mid 60s inland to near 70 at
the coast, then trend cooler to the mid 50s inland and lower 60s near
the coast by Thursday night. Lows Thursday night will be several
degrees below normal over interior areas, trending to a bit below
normal closer to the coast. /29

LONG TERM /Friday Through Monday/...The large upper low over the
eastern states shifts northward slowly through Sunday, then finally
breaks down to an open wave and ejects off to the north through
Monday. A deep layer northerly flow persists over the area through
the period as a massive surface ridge builds into the eastern
states. Dry conditions follow through Monday. Highs will be around 80
on Friday, values which are a few degrees below normal, then
gradually recover to the mid/upper 80s by Monday. Lows Friday night
will range from the mid 50s inland to the lower 60s near the coast,
a few degrees below normal, then likewise trend warmer through the
remainder of the period with lows Sunday night around 60 inland with
the upper 60s near the coast. /29

MARINE...Weak high pressure will continue over the north central
gulf through Wed then build Wed night and continue through the
remainder of the week in the wake of a cold front that moves across
the region. Expect light winds through Wed followed by a moderate
northerly flow through early Sat. A light onshore flow will develop
by the late Sat and redevelop each afternoon through early next
week. Expect less coverage of showers and thunderstorms mostly over
the near shore waters in the wake of the front through early next
week. 32/ee


.MOB Watches/Warnings/Advisories...


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