FXUS62 KFFC 301129 AAA
Area Forecast Discussion...Updated
National Weather Service Peachtree City GA
730 AM EDT Sun Apr 30 2017
.SHORT TERM /Today through Monday/...
Main focus of the short-term forecast period remains the possibility
of severe thunderstorms from early Monday morning through the
afternoon. Hi-res models are not generating much of any convection
across the forecast area today, and this makes sense considering the
warm mid-levels evident on the forecast soundings. May see some
isolated convection during the afternoon, mainly across the north.
Timing of the main line of convection associated with the system
moving out of the Mississippi Valley puts it into the northwest
sometime around or a bit after midnight and into the Atlanta metro
area by sunrise, then steadily advancing across the southern and
eastern portion of the forecast area through the afternoon. SPC
severe threat is marginal, and this seems reasonable considering the
somewhat limited instability expected during the overnight period.
Low-level shear is expected to be quite impressive however with 40-
50kt of 0-1km shear across the north. CAPE values are forecast to
remain below 600j/kg and this is supported by weak lapse rates and a
persistent warm layer in the mid-levels. This would indicate main
threats continue to be damaging wind gusts with at least some threat
for isolated tornadoes. Marginal threat for severe weather
translates into the eastern portion of the forecast area tomorrow
afternoon as low-level shear begins diminishing but instability
Based on the strong low-level jet forecast to move across the north
tonight into tomorrow morning, we will be issuing a wind advisory
for the far north, generally for our counties with elevations around
2000 feet or higher.
.LONG TERM /Monday Night through Saturday/...
Cold front will be exiting the CWFA at the very beginning of the
long term period. High pressure will briefly build across the area
on Tuesday, but begin shifting offshore by early Wednesday as the
next low pressure/frontal system moves into the central US. A second
cold front is expected to impact the CWFA Thursday, with high
pressure building in for the weekend.
Any lingering showers and thunderstorms Monday night should move out
of the area and diminish by early Tuesday morning. A dry period with
near to slightly above normal high temps is expected Tuesday through
Wednesday. Good moisture begins returning on Wednesday ahead of the
next system, but most areas should remain dry through the day
Wednesday. This is a slight change from previous forecasts.
Precip chances begin to increase Wednesday night ahead of the front.
Thursday and Thursday night should be pretty wet with on/off shra
and tsra for most of the period. The models have been pretty
consistent with bringing a line of shra/tsra through on Thursday.
There is definitely some potential for strong to severe
thunderstorms as this system moves through the area. It's too early
to call what the coverage of storms will be, but instability
parameters and forcing along the front/in the mid levels are lining
up. In addition, the potential for locally heavy rainfall exists.
Cooler temperatures are expected behind the front...and for now...a
pleasant weekend is on tap.
MVFR conditions currently across the majority of the area should
persist through 14-16Z before rising back to VFR and then scattering
out by around 18-20Z. MVFR ceilings return most areas by 08-10Z.
Winds will start out southeast 6-10kt, becoming more south southeast
by 14-16Z. Winds will increase to 8-12kt by 18-20Z w/ gusts 17-22kt
before diminishing a bit after 00Z. Cannot rule out some isolated
convection after 18Z, but I do not expect chances to be high enough
at any TAF sites to include in the forecast at this time. Line of
stronger convection will approach the metro Atlanta TAF sites 08-10Z
with occasional SHRA/TSRA 10-14Z.
//ATL CONFIDENCE...12Z UPDATE...
Medium on MVFR timing and duration.
High on remaining elements.
.PRELIMINARY POINT TEMPS/POPS...
Athens 85 68 74 53 / 20 60 70 10
Atlanta 85 67 73 55 / 10 70 80 10
Blairsville 79 64 70 48 / 30 70 80 10
Cartersville 85 65 73 52 / 20 80 80 10
Columbus 89 69 76 55 / 10 70 80 10
Gainesville 83 67 72 53 / 20 70 80 10
Macon 88 69 78 51 / 10 50 70 20
Rome 86 64 74 50 / 20 80 70 5
Peachtree City 86 67 73 51 / 10 70 80 10
Vidalia 88 70 85 57 / 10 40 60 40
Wind Advisory from 8 PM this evening to noon EDT Monday for the
following zones: Catoosa...Dade...Dawson...Fannin...Gilmer...
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