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Area forecast discussion...updated for aviation
National Weather Service Peachtree City Georgia
930 PM EDT Thu Mar 23 2017

Update...
no changes planned for the forecast.

41

Previous...
short term /tonight through Friday night/...

Rather progressive pattern expected through the short-term. Current
water vapor imagery reveals a trough across Great Basin and
southwest US...with a broad ridge located downstream from the Lee of
The Rockies into the eastern US...while cyclonic flow persists over
New England. At the sfc...a Lee cyclone is developing across
Colorado in response to the approaching trough...with associated
dryline extending to its south and a cold front to its SW...while
expansive area of high pressure dominates the eastern Seaboard and
ridges down the leeward side of the appalachian mountain range.

Despite a progressive pattern...short-term forecast will remain
quiet. Anticyclonic flow associated with center of sfc high over
northeast is responsible for moisture return/increasing cloud cover
from the south within low-level southerly flow regime today. Cooler
air associated with this airmass also keeping temps in the 60s.
Expecting a quiet end to the day as these conditions persist. Low
temps tonight will be fairly mild with mostly cloudy skies expected.
Could be some very isolated areas of light fog by daybreak
Friday...but really only expecting this in low-lying areas. T-TD
spread will be too high due to cloud cover and slightly elevated
winds for widespread fog.

Friday will be dry and warm with highs in the 70s /higher terrain
low 60s/ as mid level ridge and associated 500 mb height rises continue
to work their way into the region. Sfc high pressure that was
centered over the northeast on Thursday will shift well offshore on
Friday...but ridge influence still expected to be dominant over the
southeast. This will continue to allow lower-level moisture to
increase and clouds to persist.

Friday night will be quiet ahead of the next storm system that is
set to move in early in the long-term. Will start to see some mid
level height falls overnight as the stacked cyclone pushes into the
mid-Mississippi Valley. We again stay dry with lows in the 50s
/higher terrain 40s/.

Kovacik



Long term /Saturday through Thursday/...

Medium-range models continue to remain very progressive through the
period. No significant changes to the recent trends and little
changes made to the long term forecast grids with this cycle.
Weekend system and the early work-week system continue to show
enough instability to maintain thunder in the forecast, however both
systems also continue to show the better energy lifting north of the
state as instability wanes and shear remains limited at best. Please
see the previous long term forecast discussion below.

20

Previous long term discussion /Friday night through Wednesday/...

Surface high pressure well off-shore will continue to move further
out to sea Friday night into Saturday. Meanwhile, ridging aloft
will erode ahead of the next storm system. Expect increasing
clouds Saturday afternoon/evening as a front approaches. In the
mid- levels, a closed low dropping out of The Rockies will pivot
toward the Ohio River valley through the weekend. A cold front
associated with this system will continue to track east across the
central conus, becoming washed out before reaching Georgia. In
addition, the dynamics associated with this system will lift north
as it approaches Saturday night into Sunday. Anticipate showers
will move into northwestern Georgia Saturday afternoon/evening.
With very little surface convergence and much of the energy within
the mid-levels waning, do not have the highest confidence that
this system will hold together, especially through the day
Sunday. Therefore, current thinking is highest pops across the
northern tier of Georgia Saturday night into Sunday with the rest
of the area experiencing chance pops. Also, given weak
instability and shear, kept schc thunderstorm in Saturday evening
through Sunday. The system will lift to the north with the front
never quite making it into Georgia.

For the first half of the work-week model inconsistencies are
making confidence a bit lower. However, a progressive pattern will
continue during this time with another wave of precipitation
(showers/thunderstorms) possible Monday afternoon through
Tuesday. The ecm has another potent system approaching quickly by
mid-week under warm southerly flow. While the GFS is introducing
a distinct frontal passage by Wednesday, bringing drier and cooler
air into the region thereafter. Have hedged at the end of the
period in hopes of seeing better model continuity in time.

Under warm southerly flow through much of the long term, expect above
normal temperatures, highs primarily in the 70s.

26

&&



Aviation...
00z update...
scattered to broken clouds 040-050 should continue through much of the
night. Expect MVFR ceilings to develop just before sunrise
with some improvement by 15z. Scattering possible late afternoon
Friday. Winds east to southeast 8 to 10kt overnight increasing
again Friday after 14z to 10 to 15kt.



//Atl confidence...00z update...
medium on cloud trends...especially MVFR coverage Friday morning
high on all other elements

41

&&



Preliminary point temps/pops...
Athens 45 71 52 75 / 5 5 5 20
Atlanta 49 71 55 75 / 5 5 0 30
Blairsville 42 63 49 68 / 10 10 10 30
Cartersville 49 70 54 74 / 5 5 5 40
Columbus 53 76 57 78 / 0 0 0 30
Gainesville 46 66 52 72 / 5 5 5 30
Macon 49 76 55 79 / 0 0 0 20
Rome 49 71 54 74 / 5 5 5 40
Peachtree City 48 72 52 75 / 5 5 0 30
Vidalia 51 75 56 79 / 0 0 0 20

&&

Ffc watches/warnings/advisories...
none.
&&

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