NATIONAL WEATHER SERVICE TALLAHASSEE FL
448 AM EDT Sat Apr 5 2014
Near Term [Through Today]...
Fairly complex fcst for today as a piece of upper level energy heads eastward across the northern Gulf of Mexico into our CWA, adding additional moisture and lift to what is expected to become a quasi-stationary frontal boundary, fcst to lay out in an E-W orientation over approximately the next 24 hrs in our vicinity.
The experimental GOES Blended TPW product is showing rising PWATs over our region and to our west, peaking at over 1.5" over parts
of southern LA which is about 200% greater than normal for this
time of year.
Despite the initial lack of synoptic and mesoscale scale forcing (for the time being), this additional moisture is expected to contribute to a band of 40-50% PoPs across central and southern portions of the CWA in the form of SCT showers and thunderstorms.
While the overall forcing should be weak, the increase in PWATs, as well as SB and ML CAPEs could produce a few heavier showers and storms over parts of the FL Big Bend and Panhandle this afternoon.
However, still believe it is doubtful that any strong to severe storms will develop today, as the increase in moisture will come at the expense of less impressive mid-level lapse rates (at least over the near term period).
High temps will once again be quite tricky, as the more widespread fog and low cloudiness of Friday morning will be replaced by a more general low- mid level cloud deck as well as the developing showers and storms moving in from the west.
For now, expect temps to generally range from the lower 70s over the immediate coast and parts of SE AL to the lower 80s over the eastern FL Big Bend and near the Valdosta area of GA, where some breaks in the clouds will be possible later this afternoon.
Short Term [Tonight Through Monday]...
The first part of the short term period will be marked by a quasi-
stationary surface front becoming re-established slightly further north compared with its position this afternoon.
Combined with broad southerly low-level flow increasing in the same time period, rain is expected to develop in a ribbon of more focused isentropic ascent north of the surface front.
Model consensus indicates that the front is unlikely to completely clear north of our area in this timeframe.
Therefore, from later tonight into Sunday we are expecting a high likelihood of rain along and north of a line from De Funiak Springs, to Camilla, to Nashville GA.
PoPs were nudged up into the 70-80% range in those areas.
Further south rain chances will exist, but any showers should become more sporadic.
This configuration of rain and the surface front could set up a large temperature contrast across our area on Sunday.
The Florida Big Bend could see a mixture of clouds and sun with temperatures reaching into the low-mid 80s, whereas areas north of the front would likely see a cloudy, rainy day and could struggle to reach 70 degrees.
On Sunday Night most of the model guidance focuses QPF north or
west of our forecast area as the warm front surges north with a
deepening low over the Mid South, but the cold front remains
relatively far off to the west.
A consensus seems to be emerging for the cold front to arrive and sweep through the area during the day on Monday, which is about 6 hours later than previous model runs.
Based on the growing consensus, we focused categorical PoPs
between 12z Monday and 00z Tuesday with a west-east progression.
We still anticipate a severe weather threat from late Sunday Night
into Monday afternoon.
There is fairly good agreement on about 500 j/kg of MLCAPE ahead of the cold front, coinciding with about 50-60 knots of deep layer shear and surface dewpoints in the upper 60s.
Climatologically these values are more than sufficient for severe
thunderstorms in our area.
In fact many wind, thermodynamic, and moisture fields are very close to the median values in our local tornado climatology.
In other words, model forecasts suggest that the pre-frontal environment should be in a favorable parameter space for severe thunderstorms and even a few tornadoes.
To add some confidence to these notions, about 2/3 of the CIPS Analogs (based on the 00z GFS mass fields) for Monday were days in which we had at least one severe weather report in our area, and nearly half of the analogs were days in which we had at least one
Details still need to be worked out, but based on the consistent model signals and pattern recognition, we included severe thunderstorm wording in the forecast for Monday.
It`s also important to note that models have delayed the timing by about 6 hours - placing the thunderstorms in our area squarely during the daytime hours, a time that is usually more favorable for stronger storms.
As the previous forecaster noted, this appears to be the most robust system (in terms of favorable environments for severe storms) we`ve seen so far in 2014.
Long Term [Monday Night Through Saturday]...
Moisture will linger through Tuesday as the next shortwave moves
though the area, and some light showers are possible.
As the trough moves off to the east, ridging and high pressure will build in.
The rest of the week will be dry with high temperatures in the 70s.
Flying conditions have already run the gamut between LIFR at ECP, to IFR and TLH and VLD, and MVFR at DHN and ABY early this morning, but instead of gradually falling and bottoming out near sunrise, conditions have already begun to improve slightly at most of the terminals with the approach of the slightly higher CIGS and developing convection.
For the remainder of the period, expect generally MVFR to IFR levels to dominate the TAF sites with convective tempos (and possibly some brief gusty winds) at TLH, ECP, and VLD, corresponding with the band of 50% PoPs.
These rain chances should gradually decrease during the evening and overnight hours tonight, leading to yet another very challenging TAF forecast.
Relatively light winds and limited wave heights should linger through Sunday morning, before increasing as a low pressure system takes shape to our west.
SCEC level winds appear likely by Sunday evening, with some Small Craft Advisory winds (20+ knots) possible prior to the cold front passage on Monday.
Winds should veer to the northwest and decrease briefly on Monday night, before increasing behind a secondary cold front on Tuesday and into Tuesday Night.
Advisory level winds seem likely with this secondary front.
There likely will be a hazard to mariners on Monday from strong to severe thunderstorms.
No fire weather concerns are expected during the next several days
until the next shot of noticeably drier air arrives midweek.
Even so, conditions are not expected to become dry enough for any red flag concerns through the entire fcst period.
As of 4 AM, the only river point still above flood stage was the
Choctawhatchee River at Bruce. This river was slowly falling.
A number of other rivers remain at elevated stages, still falling from rainfall about a week ago.
Rain chances will be on the increase this weekend and into Monday before a cold front pushes through the area.
In general, heavier rainfall amounts are expected further north - over southern Alabama and southwest Georgia - or roughly along and north of a Crestview to Camilla to Alapaha line.
A general 1 to 2 inches of rain is expected over most of the area, with 2 to 3 inches north of the aforementioned line.
Isolated totals perhaps up to 4 or 5 inches will be possible across the northern and northwest parts of the area.
This will be sufficient to cause rises on most area rivers, and a few could reach flood stage by early next week.
For the latest river stages and forecasts, please visit:
Preliminary Point Temps/PoPs...
Tallahassee 80 62 80 62 81 / 50 40 30 20 80
Panama City 73 62 73 67 74 / 50 40 30 60 80
Dothan 74 56 70 64 74 / 40 70 70 60 80
Albany 76 56 71 61 78 / 30 60 70 30 80
Valdosta 83 60 82 63 82 / 50 40 40 20 80
Cross City 80 60 82 61 80 / 30 20 10 10 70
Apalachicola 73 63 74 67 75 / 40 30 20 30 80