Area Forecast Discussion National Weather Service Birmingham AL 102 PM CDT Mon Mar 19 2018
.UPDATE... MESOSCALE UPDATE.
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.SHORT TERM...
The warm front has moved through much of Central AL this morning. The frontal boundary can be denoted in the ground clutter from KBMX. Behind this warm front, we`ve been able to mix out a lot of the stratus that had been hanging around this morning resulting in clearing skies and sunshine. Here at EET, we`ve warmed to 75 over 65 with the dewpoints mixing out more (dewpoint was 67 an hour ago or so). To our west, a boundary has moved through MS and is entering western portions of Central AL. This boundary has been able to tap into the instability in the wake of the warm front, sparking some convection. This is expected to continue to move eastward across the area, initiating some thunderstorms over the next few hours. The 16z HRRR initialized well, and has a few of these thunderstorms developing through about 4-5pm CT. Severity of these storms is uncertain. With increasing instability this afternoon, I wouldn`t be surprised to see some of these storm produce hail and gusty winds. The 18z special sounding from BMX is showing right at 3000 J/kg CAPE, but the LLJ is still further west, closer to the dryline in MS, so the low level shear isn`t impressive. Therefore, the tornado threat with these scattered storms is limited.
The main concern remains for later this afternoon/evening and into the nighttime hours. The dryline has moved across the MS river in the past hour and will continue to push eastward. The higher resolution models and convective-allowing models show a broken line of individual cells developing along this dryline and moving through AL. By this time, the LLJ will have moved into the area as well, creating quite a bit of curvature in the forecast hodographs. 0-3km SRH is expected to exceed 400 by 7pm (0-1km SRH exceed 250) across much of North- Central AL, which is what led to the increase to a Moderate Risk. Expected impacts remain very similar to previous thinking - tornadoes (some may be strong), large hail up to tennis ball sized, and damaging winds.
This line of storms will move from the northwest to southeast through tonight and should move out of our area by the midnight to 2am timeframe.
TUESDAY 3/20 Severe thunderstorms in east SC, southeast GA, north and central FL peninsula. TORCON - 4 north FL; 3 central FL, east SC; 2-3 southeast GA.
A warm front moves into northeast SC and a secondary surface low develops there, while a cold front moves across FL and an upper trough moves across the Southeast. A strong low-level westerly low-level jet gives strong wind shear, but surface winds may have veered to southwest, so there is a question about how many tornadoes will occur. Damaging winds in bow echoes are likely.
Area Forecast Discussion National Weather Service Tampa Bay Ruskin FL 800 AM EDT Tue Mar 20 2018
.AVIATION... Low ceilings around 500-1000ft are the main concern this morning, with some patchy MVFR to IFR fog also occurring. Showers and thunderstorms will move into the area from north to south, beginning late this morning and continuing through the evening hours. Winds will be breezy with high gusts through the day. Rain should move out and winds calm a bit after 01z, with VFR conditions returning.
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.Prev Discussion... /issued 430 AM EDT Tue Mar 20 2018/
..STRONG TO SEVERE THUNDERSTORMS POSSIBLE TODAY...
SHORT TERM (Today through Wednesday)... A strong cold front is on track to move south through the Florida Peninsula today and tonight. Continued southwest low level flow ahead of this front has brought surface dew points up to the upper 60s and low 70s across the area, leading to widespread fog/mist and low stratus across the area early this morning. However, winds are breezy enough to keep the fog from getting particularly dense, so visibilities are generally expected to remain around 2 miles or greater through around sunrise.
With the moist airmass in place ahead of the front and breezy winds aloft producing strong wind shear, numerous showers and thunderstorms are expected to develop ahead of the front and spread south through the area today. With such strong shear and cool mid level temperatures, conditions are in place for some of the storms to become severe, with damaging wind gusts, hail, and isolated tornados all possible. Apart from the storms, a tight pressure gradient along the frontal passage will also produce gusty winds across the area this afternoon. As a result, a Lake Wind Advisory is in effect for this afternoon into early this evening for the entire area. In addition, the breezy onshore flow will lead to a high risk of rip currents along area beaches this afternoon through Wednesday evening.
Showers and thunderstorms will clear out from north to south this afternoon through early this evening, with clearing, but still breezy conditions filling in overnight. Temperatures will be cooler on Wednesday, with highs in the upper 60s to mid 70s under sunny skies.
LONG TERM (Wednesday Night through Monday)... Broad troughing will remain across the eastern half of the country as ridging builds over the west and then shifts eastward through the end of the week. At the surface, high pressure will build over the southeast through Thursday, with a cool and dry air mass in place over Florida. Highs will top out in the upper 60s to lower 70s under sunny skies.
As we head into Friday and the weekend, mid/upper-level ridging will gradually build over the Gulf of Mexico and Florida as surface high pressure gets pushed out into the Atlantic. This will lead to warming temperatures each day through Sunday. Friday will still nice, with highs only a few degrees above those for Thursday, but temperatures continue to increase for both Saturday and Sunday, ending up in the mid 80s across parts of the interior for Sunday. This pattern is generally forecast to persist into the start of next week ahead.
AVIATION... Widespread MVFR ceilings and visibilities with isolated IFR ceilings will continue overnight, with areas of IFR ceilings expected to increase in coverage closer to sunrise. Showers and thunderstorms will spread south into the Tampa Bay area terminals during the morning hours, and into southwest Florida during the afternoon hours, with gusty winds turning to westerly. Showers and storms will clear out from north to south during the late afternoon and early evening, but breezy winds are expected to hold overnight.
MARINE... Southwest winds will increase today across the coastal waters ahead of an approaching cold front with numerous thunderstorms and advisory level winds and seas spreading across the area by this afternoon and evening. Winds will turn to the northwest overnight behind the front, remaining breezy through Wednesday morning before beginning to subside through the afternoon and evening hours. High pressure with then fill in Thursday through the weekend, with winds holding around 15 knots or less.
FIRE WEATHER... A cold front will move south through the area today with numerous thunderstorms and breezy winds, leading to high dispersion values over the interior. Much drier air will then fill in Wednesday, with critical humidity values expected during the afternoon for much of the area.
.TBW WATCHES/WARNINGS/ADVISORIES... FL...High Rip Current Risk from 2 PM EDT this afternoon through Wednesday evening for Coastal Charlotte-Coastal Hillsborough-Coastal Lee-Coastal Manatee-Coastal Sarasota-Pinellas.
Lake Wind Advisory from 1 PM this afternoon to 8 PM EDT this evening for Coastal Charlotte-Coastal Citrus- Coastal Hernando-Coastal Hillsborough-Coastal Lee- Coastal Levy-Coastal Manatee-Coastal Pasco-Coastal Sarasota-DeSoto-Hardee-Highlands-Inland Charlotte- Inland Citrus-Inland Hernando-Inland Hillsborough- Inland Lee-Inland Levy-Inland Manatee-Inland Pasco- Inland Sarasota-Pinellas-Polk-Sumter.
Gulf waters...Small Craft Advisory from noon today to 1 PM EDT Wednesday for Coastal waters from Tarpon Springs to Suwannee River FL out 20 NM-Waters from Englewood to Tarpon Springs FL out 20 to 60 NM-Waters from Tarpon Springs to Suwannee River FL out 20 to 60 NM.
Small Craft Advisory from 9 PM this evening to 1 PM EDT Wednesday for Charlotte Harbor and Pine Island Sound- Coastal waters from Bonita Beach to Englewood FL out 20 NM-Coastal waters from Englewood to Tarpon Springs FL out 20 NM-Tampa Bay waters-Waters from Bonita Beach to Englewood FL out 20 to 60 NM.
NWS SPC ✔ @NWSSPC 8:01am CDT #SPC Day1 Outlook Enhanced Risk: over central/northern florida and coastal areas of georgia, south carolina and southern north carolina http://go.usa.gov/YWq5
Jacksonville State University 9 hrs · Please do not come to campus to check out the damage. Many roads are impassible, street lights are out, and first responders are trying to do their jobs. Many key university personnel have not been able to report to campus. We are in emergency mode - protecting life, ensuring everyone is safe and accounted for, getting everyone shelter. We wont know the full extent of the property damage until the sun comes up. We have received numerous questions about when students will be allowed back in damaged residence halls. We are not able to answer that question right now. We will notify residents when and if that is possible. For now, we are focused entirely on search and rescue.
@ReedTimmerAccu 2h2 hours ago More Nearly all of Jacksonville State University is severely damaged. Spoke to a student who road out the #tornado in a bath tub. Thank god most students were off on spring break. Long-track wedge with huge terrain/orography influence on damage @breakingweather 0:07 16 replies 144 retweets 159 likes Reply 16 Retweet 144 Like 159 Direct message
URGENT - IMMEDIATE BROADCAST REQUESTED Tornado Watch Number 22 NWS Storm Prediction Center Norman OK 1200 PM CDT Wed Mar 28 2018
The NWS Storm Prediction Center has issued a
* Tornado Watch for portions of Western and central Louisiana Southeast and east Texas Coastal Waters
* Effective this Wednesday afternoon and evening from NOON until 900 PM CDT.
* Primary threats include... A couple tornadoes possible Scattered large hail and isolated very large hail events to 2 inches in diameter possible Isolated damaging wind gusts to 70 mph possible
SUMMARY...Severe thunderstorms are expected to become more common across the watch area through the remainder of the afternoon, offering damaging gusts, isolated large hail, and the potential for a couple tornadoes.
The tornado watch area is approximately along and 75 statute miles north and south of a line from 65 miles north northwest of Palacios TX to 25 miles north northeast of Alexandria LA. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU2).
PRECAUTIONARY/PREPAREDNESS ACTIONS...
REMEMBER...A Tornado Watch means conditions are favorable for tornadoes and severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings.
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AVIATION...TORNADOES and A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE and ALOFT TO 2 INCHES. EXTREME TURBULENCE and SURFACE WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM MOTION VECTOR 25030.
@USTornadoes Preliminary summary of the multi-day tornado event from April 13-15. Over two dozen tornadoes confirmed so far. We will update as numbers are finalized: https://bit.ly/2EQo8NY
The southern jet stream has been suppressed for most of the time in 2018 so far since January, because of persistent upper level troughing pattern over the Eastern portions of the continent due to a prolonged negative North America Oscillation, in place since the beginning of March. It has only been within the past week or so in which we finally saw the southern jet become active, bringing some severe weather across the parts of Texas, eastward along the Gulf Coast into the Deep South.
Long range GFS still is hinting at potential strong ridging across Greenland, which if this manifests, would suggest that the -NAO could continue into the first week of May at least.
BTW, NWS Jax office mets are saying a possible low-end EF-1 twister which occurred in Camden County, GA on last Sunday. Many trees were reported down in Harriett's Bluff, about 40 miles north of downtown Jacksonville.
