Area Forecast Discussion
Issued by NWS
FXUS62 KTAE 031436
Area Forecast Discussion
National Weather Service Tallahassee FL
1036 AM EDT TUE MAY 3 2016
.NEAR TERM [Through Today]...
The first hints of deep convection are already showing up across
the area on radar and visible satellite. This lines up well with
the projected convective temperature of 77 degrees from the 12Z
Tallahassee sounding, and current surface temperatures rising
through the mid-upper 70s. The atmosphere should continue to
quickly destabilize this morning, and by midday (based on a
modified TAE sounding) we should have around 2000-2500 j/kg of
SBCAPE available across much of the forecast area. Additionally,
vertical wind shear is projected to gradually increase through the
course of the day, with effective bulk shear reaching around 35 to
40 knots by the mid afternoon. Such an environment should be
supportive of severe storms, and even some supercells. With
relatively straight hodographs, splitting supercells and small
clusters and lines should be the primary convective mode. The
Storm Prediction Center has upgraded the northern half of our
forecast area to a Slight Risk, and this seems reasonable.
The 12Z Tallahassee sounding indicated mid-level (700-500mb) lapse
rates of 6.9 C/km, which is around the 80th percentile for this
time of year per our climatology. The overlap of moderate
instability and shear, and steep mid level lapse rates favors a
large hail threat. This is borne out by a wide variety of model
forecast soundings - both by the model type and location. Sounding
analogs indicate a large number of matches to a historical large
hail sounding database, and the significant hail parameter on most
models is forecast to rise above 1 this afternoon (indicative of a
favorable environment for large hail). Surrogate severe
probabilities from a couple hi-res ensembles agree with this
assessment and indicate a corridor of higher hail probabilities
extending into our forecast area this afternoon. Damaging winds
would also be possible, but large hail may actually be the main
threat, especially with any splitting supercells.
Most of the forecast elements in the forecast were not changed
substantially. PoPs remain around 70-80% along and north of I-10
this afternoon, with highs in the low-mid 80s. More extensive
severe storm and large hail wording was incorporated into the
forecast, though, to match the risk upgrade from SPC. The storms
should be most numerous in the 19-23Z timeframe per both CAMs and
.PREV DISCUSSION [544 AM EDT]...
.SHORT TERM [Tonight Through Thursday]...
At the start of the short term period, the cold front will be
slowly moving through the forecast area with scattered storms
expected overnight, mainly along and southeast of a line from
Apalachicola to Valdosta. As the overall Eastern CONUS trough
amplifies and shifts eastward across the Mid South, this will
start the process of shifting the deep layer moisture further
south and east away from the region, with the surface cold front
passing through the forecast area shortly after daybreak on
As a deep upper low settles across the Southern Appalachians on
Thursday, expect dry and cool conditions across the region.
Temperatures are expected to drop to around 10 degrees below
climatology for early May, so highs only in the mid 70s are
.LONG TERM [Thursday Night Through Tuesday]...
The cool snap will continue through Friday night as the upper low
remains over Eastern South Carolina. By Saturday, this system will
get picked up by the northern stream and move out into the Western
Atlantic. Ridging aloft will build in its place across the South,
allowing for a steady warming trend through the weekend. Dry
weather will continue through the end of the long term period.
High temperatures by Sunday and beyond will warm back into the
upper 80s to near 90.
.AVIATION [Through 12Z Wednesday]...
Areas of fog have developed with MVFR/IFR CIGS/Vis impacting most
TAF sites. LIFR conditions were occurring at ECP. CIGS/Vis will
gradually improve shortly after daybreak. Numerous TSRA will
develop by afternoon as a cold front moves slowly southeast across
the region. Rain should end across all but VLD by the end of the
Southwesterly winds ahead of a cold front will shift to offshore
on Wednesday and increase to cautionary levels through Thursday
night. Light winds and low seas are expected to return by Friday
and continue into the weekend.
High dispersion values are forecast for Wednesday due to stronger
winds and deep mixing. Also, afternoon relative humidity values may
drop below critical levels over some inland areas Thursday and
Friday. However, red flag conditions are not expected at this time.
Hi-res guidance suggests widespread 1-1.5 inches of rain across
South Alabama and Georgia will be quite common today, with
locally heavier totals with the stronger storms. Overall, this
shouldn`t present a flood risk outside of any heavy downpours in
urban areas. Dry conditions return on Wednesday and continue for
the next several days. Thus, there are no river flood concerns.
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 85 66 81 57 78 / 80 40 10 0 0
Panama City 78 67 78 63 75 / 50 20 10 0 0
Dothan 80 60 77 56 73 / 70 30 0 0 0
Albany 83 62 78 56 73 / 80 40 0 0 0
Valdosta 85 65 80 56 76 / 70 50 10 0 0
Cross City 85 68 82 59 80 / 30 60 30 0 0
Apalachicola 80 68 79 63 77 / 40 30 10 0 0