Area Forecast Discussion
Issued by NWS Mobile, AL

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FXUS64 KMOB 191638 AAB

Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
1038 AM CST Fri Jan 19 2018

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


.UPDATE...Quick update to zones to remove Hard Freeze Warning
headlines which expired. /10


.PREV DISCUSSION... /issued 524 AM CST Fri Jan 19 2018/

DISCUSSION...Updated for latest aviation discussion below.

12Z issuance...VFR conditions expected through the forecast. The
area will see an increase in mid level clouds from the west as
onshore flow becomes more organized tonight, but am not expecting
this to impact operations.


PREV DISCUSSION... /issued 449 AM CST Fri Jan 19 2018/

NEAR TERM /Now Through Friday night/...An upper shortwave shifts
lowly east from over the Southern Plains to over the Lower
Mississippi River Valley. This shifts surface high pressure
centered over western potions of the Southeast to over eastern
portions, restoring onshore flow over the Lower Mississippi River
Valley and western-most portions of the Southeast by sunrise
Saturday. With most organized southerly flow occurring over-night
tonight, today will be pretty dry. With mostly sunny skies,
guidance is consistent in advertising temps around 10 degrees
warmer today than yesterday. There is variation between models of
a few degrees, especially over southeast Mississippi (NAM
coldest/ECMWF warmest)due to different handling of a band of
snow/ice melting over the Southeast. Late in the day visible
satellite shots yesterday hard to get to pick out the state of the
frozen stuff with temps getting back below freezing, so am
assuming there is some around and am leaning towards the middle to
cooler end of the guidance for highs today. With highs getting up
in the 50s, do feel little frozen stuff will be around by

Tonight, with the onshore flow becoming more organized, wild card
is a mid level stratus deck guidance is advertising moving over
the forecast area from the west. Guidance varies on handling the
amount overnight (and radiational cooling), with varying lows the
result. Have went with a blend to work through these differences.
Still, another night of below seasonal temps is the result. /16

SHORT TERM /Saturday Through Sunday night/...A 1025 mb surface
high pressure area across the southeast states will move very
slowly eastward over the western Atlantic, but a trailing surface
ridge will remain across the southeast states and northeast Gulf
of Mexico through Sunday night. A light southerly to southeasterly
wind flow will resume across the forecast area over the weekend
along the western periphery of the surface ridge, bringing
increasing low level moisture and the potential of patchy fog late
Sunday night. An upper shortwave extending from the Mid-Atlantic
region to the western Gulf of Mexico will move slowly east over
the region with little fanfare as the mid layer remains very dry.
As a result, rain-free conditions should remain through the short
term, with only isolated light rain showers possible late Sunday
night across our extreme southwest zones as the low level
moisture increases. /22

LONG TERM /Monday Through Thursday/...A strong upper level low
pressure area over the central Great Plains will move east-
northeast, reaching New England by late Tuesday night. An
associated surface low pressure area, also over the central Great
Plains, will move east-northeast to New England by late Tuesday
night as well. An associated cold front will approach the region
from the west on Monday, moving through the forecast area Monday

This pattern will bring widespread rain to the forecast area on
Monday, along with a slight chance of embedded thunderstorms. A
100 to 130 knot jet stream along the periphery of the upper low
will develop over the eastern conus on Monday, putting our area in
the right entrance region of the upper jet. This enhanced lift
across the area, along with the models trending toward higher
instability and upper level lapse rates, could promote a higher
chance of thunderstorms on Monday.

A few thunderstorms could become strong with gusty winds and
small hail due to a dry mid level air mass. Widespread rainfall
amounts around one-half inch should occur, with locally higher
amounts near one inch possible. The precipitation will then end
from west to east Monday evening. Dry conditions will follow
through Thursday as high pressure once again settles over the
region. /22

MARINE...Surface high pressure over the Lower Mississippi River
Valley will shift to the East Coast into the weekend, restoring
onshore flow to the area. A front will move across the area Monday
night, bringing a return off offshore flow. With surface high
pressure slowly passing north of the area through mid week, winds
slowly shift to a general east to southeast by the end of the
coming work week. /16




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