Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 171549 AAC
AFDMOB

Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
949 AM CST Tue Jan 17 2017

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

&&

.UPDATE...Latest observations show that morning fog has been slowly
lifting with a net improvement in visibility. Any lingering, patchy fog
should lift entirely by the end of the morning.

17.12Z upper air map analysis shows an amplified deep layer ridge
positioned over the northwest Caribbean and the southern Gulf. To the
west and north of this ridge, an east Pacific connection of moisture
was streaming northeast across northern Mexico into the southeastern
US within a well established high level southwest flow. At the
surface, a cold front was draped from the Ohio River Valley to the
upper Texas coast. An assessment of deep layer moisture (pwat values)
east of the frontal zone shows values from near 1 inch over northern
Alabama to around 1.4 inches over the lower Texas coast. From a
climatological perspective, these values are near 180% of normal.
Despite the modified layer moisture, the better forcing for showers
will be closer to the frontal zone to our west. Thus, will maintain
only a slight chance of showers today. For temperatures, no changes.
Will continue to see daytime highs from the mid to upper 70s, being
well above climatic normals. /10

&&

.PREV DISCUSSION... /issued 636 AM CST Tue Jan 17 2017/

DISCUSSION...See updated information for land areas and aviation
discussion below.

UPDATE...Updated zone forecast to headline a High Risk of rip
currents along the beaches of Alabama and the northwestern Florida
panhandle.

AVIATION...
17/12Z issuance...Patchy fog limiting vsbys in some locations this
morning, but only MOB reporting vsby less than 1/4 mile at times.
Generally only light fog with no substantial restrictions for most
locations. Fog dissipates by midmorning, but returns tonight. Surface
winds south to southeast 5 to 10 knots through tonight. 12/DS

PREV DISCUSSION... /issued 519 AM CST Tue Jan 17 2017/

NEAR TERM /Now Through Tuesday night/...Surface high pressure will
continue to ridge into the forecast area from the east through
tonight, while a weakly defined surface frontal bondary initially
extending from northern Alabama, across Mississippi and into northern
Louisiana early this morning drifts slightly south and east through
tonight (but remains just to the northwest of our forecast area).
Aloft a high pressure ridge remains centered over the southeastern
Gulf of Mexico. This pattern will maintain a deep layer south to
southwest flow over our area. Overall this means little change to the
observed weather over the near term period. The moist onshore flow
has again allowed patchy fog to develop across portions of the region
this morning, and expect more of the same tonight. Currently, except
at a few locations, fog is not dense although some areas will
possibly see visibilities drop to 1/4 mile or less both early this
morning and again late tonight. Will monitor for DFA criteria, but at
this time not widespread enough to warrant an Advisory. No real
forcing of note today or tonight, but with the continually moistening
airmass (PWATs ~ 1.2 inches) could see some isolated showers later
today. Could be a few embedded thunderstorms over northwestern
counties where greatest instability will be. Otherwise will continue
to see temperatures that are well above climatic normals. Highs today
in the mid to upper 70s most locations, lows tonight ranging from the
upper 50s interior to lower 60s at the coast. 12/DS

SHORT TERM /Wednesday Through Thursday night/...Deep cut off low in
the mid to upper levels gradually shifts east northeast over the
central plains states wed through thu...becoming negative tilted
further south over the lower ms river valley and north central gulf
states late thu and thu night as a strong 40 to 50 kt h8 jet shifts
east from la/ms to al/nwfl from early thu afternoon through thu
evening. Also...the RRQ of an h2 upper jet is noted moving from the
lower ms river the tn river valley through thu evening supporting
a strong divergence signal aloft. At the sfc high pressure continues
along the eastern seaboard with a developing sfc low in the vicinity
of the upper low over the central conus. By thu afternoon mucapes
climb to around 1000 j/kg leading to good convection initiation in
the lower levels for this time of the year. As a result better
thunderstorm development is expected on thu with a few strong to
severe thunderstorms possible thu afternoon and thu evening.
Damaging straight line winds and large hail will be possible with the
stronger thunderstorms during the thu afternoon/thu evening
timeframe. Currently...a marginal risk for severe weather has been
posted by SPC in the day 3 outlook. Skies will be mostly cloudy
through the short term period with high temps generally ranging from
lower to middle 70s with lows mostly in the upper 50s to lower 60s.

LONG TERM /Friday Through Monday/...By fri the better dynamics
aloft moves off to the northeast with the main upper trof in the mid
to upper levels still well off to the west...progged to shift east
across the lower half of the country over the weekend and early next
week. With this pattern expect another round of strong upper level
forcing combined with slightly better sfc based instability possibly
leading to another round of strong to severe thunderstorms moving
across the forecast area sat afternoon through early sun morning.
Damaging straight line winds...large hail along with isolated
tornadoes can`t be ruled out with the stronger storms. Skies will
remain mostly cloudy fri through mon with high temps mostly in lower
to middle 70s fri thru sun with lows ranging from the mid 50s well
inland and the lower 60s closer to the coast. By mon a surface cold
front moves across the region leading to cooler temps mon and mon
night with light rain possible mostly in the morning. Skies begin to
clear from west to east by late mon afternoon. 32/ee

MARINE...High pressure off the mid Atlantic coast will continue to
ridge west across the marine area through early Wednesday then
weaken Thursday and Thursday night as a cold front moves east toward
and then across the coastal waters. This front stalls near the Gulf
Coast Friday and Saturday, then another stronger front approaches
from the west on Saturday. Showers and thunderstorms can be expected
with each front. A general mostly onshore light to sometimes
moderate (especially towards end of the week and early weekend) flow
is expected through the forecast period. 12/DS

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...High Rip Current Risk until 6 PM CST this evening for ALZ265-266.

FL...High Rip Current Risk until 6 PM CST this evening for FLZ202-204-
     206.

MS...None.
GM...None.
&&

$$

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