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Show Area Forecast Discussion - Tallahassee, FL (TAE) (Florida Panhandle) Selection: |
| #516360 (Received by flhurricane at: 9:59 PM 05.Jun.2012) AFDTAE AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 952 PM EDT Tue Jun 5 2012 .DISCUSSION... The 00 UTC regional surface analysis showed a "wavy" cold front from Southeast GA to northern LA, with a weak 1008 mb low over Southeast GA. Most of the thunderstorms that developed earlier today have diminished, but based on the 00 UTC KTAE sounding and RAP output, there is plenty of deep layer moisture & instability for more showers and storms through the night. Any upstream upper level disturbances or outflow boundaries could trigger new storms. It appears that the severe threat has mostly ended, given the decreased CAPE and 500 mb wind speeds. && .AVIATION... Scattered showers and thunderstorms will continue to move across the Tri-state region this evening and overnight. Patchy fog will develop after midnight with the best chance of MVFR/IFR VSBYs/CIGs at ABY and VLD. Conditions will return to VFR at all terminals shortly after sunrise with another round of scattered to numerous thunderstorms by afternoon. && .TAE WATCHES/WARNINGS/ADVISORIES... AL...None. GA...None. FL...None. GM...None. && $$ |
| #516272 (Received by flhurricane at: 3:14 PM 05.Jun.2012) AFDTAE AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 308 PM EDT Tue Jun 5 2012 ...Severe Thunderstorm Watch 358 in Effect until 9 PM EDT... .MESOSCALE DISCUSSION... So far the evolution of deep moist convection has not worked out quite as expected. It appears that our local 12 UTC 4km WRF has initialized the best among the latest NWP guidance. It simulates the strong convection just to our north, but keeps these cells propagating east southeast along the cold front just to our north (which is what has happened so far, and is supported by the analyzed deep layer wind fields). This model also initiated convective cells over our western zones later this afternoon as a well-defined mid level MCV (currently over South Central AL) approaches and interacts with the FL Panhandle sea breeze front (or any other mesoscale boundaries). These storms, some of which could be strong to severe, move east through the evening but weaken due to evening cooling and/or moving into a more stable airmass, where SBCAPE values were only about 1000 J/KG or less (based on the KTAE 18 UTC sounding, the weak CU field observed on visible imagery, and latest RAP analyses). Because of the complexity of this forecast, there are other scenarios that could occur and we don`t want to minimize the threat for severe storms with a convective watch in effect. However, recent analyses and model output do suggest that the overall threat may be a little less than what we expected prior to this afternoon. To summarize, we now think the highest threat for isolated severe storms will be in the FL Panhandle and Southeast AL this afternoon and evening, but there is still a low-end threat elsewhere until later this evening. && .SHORT TERM (Tonight through Thursday night)... Low end severe threat will continue into this evening, but should end before midnight as the MCV passes southeast of the area and the boundary layer stabilizes. PoPs are held in the likely range over our GA zones and inland FL Big Bend north of the interstate. Conditions will not be quite as favorable for severe weather across the area tomorrow. The primary MCV will be southeast of the area and there do not appear to be any others lurking upstream. However, the frontal boundary will be pulling up stationary during the day, roughly bisecting the forecast area from ENE to WSW, or roughly from Savannah to Bainbridge to Pensacola. Shear values drop off considerably. However, with northwest flow aloft and a juicy air mass along and south of the front, we will still need pretty high PoPs (likely to categorical) across the southeast half of the forecast area. Some drying will occur north of the front and PoPs taper to low end chance (30) over Quitman County. Will only include mention of isolated T+ for the higher PoP areas. SPC has the area in a 5% risk area east of the Apalachicola River. The front will gradually become more diffuse as we head through Wednesday night into Thursday. PoPs will taper from 60 far southeast to 20 far northwest Thursday afternoon. The dry push from the northwest will continue Thursday night and it is about that time that we will finally see the long wave trough pull away to the northeast. .LONG TERM (Friday through next Tuesday)... Models continue to be in reasonably good agreement. The large scale longwave pattern continues highly amplified highlighted by a deep trough over extreme wrn Pac/wrn U.S, ridging over Cntrl Conus with axis down plains, and a positively tilted trough from low well east of Canadian Maritimes WSW into Mid South and NRN Gulf region. At surface, front responsible for recent weather aligned WSW to ENE across coastal Gulf anchored by lows on MS coast and well east of GA. Thus the juxtaposition of trough/front will keep the FL counties and S/Cntrl GA in a moist unstable onshore flow with chances of locally heavy rainfall especially in the FL Panhandle and Big Bend. Conversely, SE AL/SW GA will be increasingly dominated by high pressure diving out of OH Valley and dry air overspreading NW-SE across SE AL. Clouds and rain will keep max temps in the upper 80s to low 90s, but higher over SE AL. As the wrn trough moves ewd thru Intermountain region thru Fri then thru the Plains on the weekend, Cntrl ridge builds into Ern region while Ern trough pushes increasingly offshore beginning Friday. By late Friday, this will push front further swd where it will likely dissipate over the Nrn Gulf while the surface high moves Ewd into the Wrn Atlc with local flow veering to onshore into at least Monday. POPs will return to at or below normal, especially across AL/GA. Both the Euro and GFS agree on a cut off low approaching the area from the west at the end of the extended term. This combined with moisture return on back side of high off east coast will bring chance pops back to the forecast Mon and Tues, but mainly for WRN Panhandle and SRN Al. With southerly flow, we will begin trending towards warmer temps with highs into the mid 90s and lows near 70. && .MARINE (Tonight through Sunday)... Winds are beginning to increase out over the marine area as the gradient tightens ahead of an approaching front. Exercise caution conditions are forecast through tonight. After that, the front will get close enough that the gradient will weaken somewhat which will bring winds down below headline criteria. The front is expected to stall north of the waters tomorrow and remain in place through Thursday before dissipating. High pressure will then build from the Appalachians southeast to a position off the Carolina Coast over the weekend. This will set up a period of east to southeast flow. && .AVIATION (through 18Z Wednesday)... Thunderstorms will be possible at all terminals through the afternoon and evening hours. Initial development will be around TLH with the other TAF sites getting in on the action a bit later on. IFR ceilings will be possible at ABY and VLD overnight. With likely to categorical PoPs in the forecast for Wednesday, convection will need to be added to the terminal forecasts with the next (00Z) package. && .FIRE WEATHER...Red flag conditions are not expected over the next few days. && .PRELIMINARY POINT TEMPS/POPS... Tallahassee 71 88 72 89 70 / 50 80 60 50 30 Panama City 74 88 73 88 74 / 50 70 50 40 20 Dothan 71 90 70 92 71 / 50 50 40 30 10 Albany 71 88 69 90 69 / 70 40 40 30 10 Valdosta 70 86 69 88 69 / 70 70 50 50 40 Cross City 71 86 72 87 69 / 40 80 60 60 50 Apalachicola 74 87 73 86 73 / 50 60 60 50 20 && .TAE WATCHES/WARNINGS/ADVISORIES... AL...None. GA...None. FL...None. GM...None. && $$ |
| #516246 (Received by flhurricane at: 12:47 PM 05.Jun.2012) AFDTAE AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 1244 PM EDT Tue Jun 5 2012 ...Severe thunderstorm threat beginning to materialize... .MESOSCALE DISCUSSION... The NWS has issued a Severe Thunderstorm Watch through early this evening for most of our forecast area, as it appears that scattered strong to severe thunderstorms were beginning to develop to our north in Central GA and AL along a cold front. We are also concerned that isolated strong to severe storms may form in our FL zones ahead of an approaching MCV (currently over central AL) and/or along mesoscale boundaries like sea breeze fronts. Local VAD wind profiles showed 0-6 km vertical wind shear magnitudes around 35 KT, and the latest RAP SBCAPE values were a healthy 2000 J/KG in areas where CS was not dense. The 12 UTC KTAE sounding was a bit more unstable than forecast by the NAM yesterday, with 700-500 mb lapse rates from 6.5 to 7 deg per km. We are doing a special Upper Air sounding to better assess the local environemt. Large scale forcing & mesoscale forcing, ample deep layer moisture and potential instability, and adequate (if not spectacular) deep layer shear will all combine for a threat of severe storms this afternoon and evening, with damaging wind gusts and large hail being the main threats. It already appears that the storms developing to our north were exhibiting rotation and hail cores aloft, and this should be a good proxy for what we can expect later. Please stay tuned for the latest updates and warnings. && .TAE WATCHES/WARNINGS/ADVISORIES... AL...None. GA...None. FL...None. GM...None. && $$ |
| #516236 (Received by flhurricane at: 11:17 AM 05.Jun.2012) AFDTAE AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 1110 AM EDT Tue Jun 5 2012 ...Severe storms possible this afternoon and evening... .UPDATE...Well-defined MCS/MCV over southwestern Alabama has begun to weaken this morning. However, the triggering shortwave remains well-defined and will continue to press east-southeast through the afternono. Hi-res guidance has not handled the evolution of the MCS well, with most guidance taking it from Arkansas south through Louisiana overnight. This leads to low-confidence in the convective evolution shown by the hi-res guidance. Looking at observational data this morning indicates the potential for an active day of convection across the forecast area. This morning`s 12Z sounding indicated significantly more deep layer moisture and steeper mid- level lapse rates than Monday morning. PWAT has increased to around 1.4 inches, with mid-level lapse rates above 7C/KM. The 12Z regional surface analysis also supports an abundance of moisture as we see higher dewpoints ahead of the MCS in the western Panhandle of FL and southeastern AL. Since we are seeing these higher dewpoints, we are not expected to mix out as much as we saw Monday so CAPE values have the potential to reach upwards of 3000 J/kg. The instability combined with an abundance of potential boundary interactions (the outflow boundary from the MCS, small- scale convergent bands along coastal areas, differential heating boundaries along the MCS cirrus shield, etc), as well as increasing mid-level flow with the approach of the shortwave, should lead to numerous showers and thunderstorms this afternoon and evening, with the potential for damaging winds and large hail. && .AVIATION (through 12z Tuesday)...VFR conditions are expected at most terminal through the early afternoon, before widespread showers and thunderstorms develop and continue into the evening. Could see some gusty winds with storms approaching terminals. The thunderstorms activity may extend into the overnight hours. In additions, terminals which see precip may see IFR to MVFR conditions develop by morning. && .MARINE...A weak front slowly approaching from the north will tighten the gradient over the coastal waters this afternoon with winds reaching exercise caution criteria. Previous forecast package handled this pretty well, so only made minor changes to the forecast for the morning issuance. && .PRELIMINARY POINT TEMPS/POPS... Tallahassee 92 72 88 71 91 / 40 60 60 40 40 Panama City 88 74 87 73 88 / 40 60 60 30 40 Dothan 90 71 90 70 93 / 70 60 50 30 30 Albany 91 71 88 68 92 / 70 60 50 30 30 Valdosta 91 71 88 67 90 / 60 60 60 40 40 Cross City 89 72 86 70 88 / 40 50 60 40 50 Apalachicola 88 75 86 72 85 / 40 50 60 40 50 && .TAE WATCHES/WARNINGS/ADVISORIES... AL...None. GA...None. FL...None. GM...None. && $$ |
| #516183 (Received by flhurricane at: 4:26 AM 05.Jun.2012) AFDTAE AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 405 AM EDT Tue Jun 5 2012 ...Slight Risk of Severe Thunderstorms This Afternoon & Evening... .SHORT TERM... (Today through Thursday) The forecast area will remain under northwesterly upper level flow today with our main concern being any upstream short waves which could trigger convection. One such shortwave is over Mississippi currently with a well defined mesoscale convective vortex (MCV) evident on satellite imagery. This is forecast to move into our area this afternoon into tonight and provide a focus for a fairly high coverage of showers and thunderstorms, some of which could be strong to severe. In terms of severe chances today, both the GFS and especially NAM show higher levels of CAPE than what we saw on Monday with dewpoints not mixing out as much. In fact, SBCAPE values could approach 3000 j/kg if the NAM is right. However, given that we mixed out significantly on Monday over inland areas, there is some concern that it could be a bit overdone. Still, decent instability is expected this afternoon and with that MCV approaching, storms are expected to develop. Deep layer shear values also do not look quite as high for today as they once did yesterday. Overall, there is still a threat for some severe storms, so enhanced wording will be maintained in the forecast. PoPs are also a little tricky for today due to the possibility of a later timing of the storms in some areas. For instance, our 00z local WRF shows no convection in Tallahassee prior to the early evening hours. PoPs were cut back some for the daytime hours and increased some for overnight to account for this possibility. On Wednesday, confidence is low on how things will play out due to uncertainty with how convection this afternoon and tonight will impact the air mass. However, with a frontal boundary still in the area, a decent coverage convection is expected for Wednesday. The severe threat currently looks marginal. By Thursday, the front will still be in the area with the best focus for convection across the southern half of the forecast area. .LONG TERM... (Thursday night through next Tuesday) Models continue to be in reasonably good agreement. The large scale longwave period continues highly amplified highlighted by a deep trough over extreme wrn Pac/wrn U.S, ridging over Cntrl Conus with axis down plains, and a positively tilted trough from low well east of Canadian Maritimes WSW into Mid South and NRN Gulf region. At surface, front responsible for recent weather aligned WSW to ENE across coastal Gulf anchored by lows on MS coast and well east of GA. Thus the juxtaposition of trough/front will keep the FL counties and S/Cntrl GA in a moist unstable onshore flow with chances of locally heavy rainfall especially in the FL Panhandle and Big Bend. Conversely, SE AL/SW GA will be increasingly dominated by high pressure diving out of OH Valley and dry air overspreading NW-SE across SE AL. Clouds and rain will keep max temps in the upper 80s to low 90s, but higher over SE AL. As the wrn trough moves ewd thru Intermountain region thru Fri then thru the Plains on the weekend, Cntrl ridge builds into Ern region while Ern trough pushes increasingly offshore beginning Friday, By late Friday, this will push front further swd where it will likely dissipate over the Nrn Gulf while the surface high moves Ewd into the Wrn Atlc with local flow veering to onshore into at least Monday. POPs will return to at or below normal, especially across AL/GA. Both the Euro and GFS agree on a cut off low approaching the area from the west at the end of the extended term. This combined with moisture return on back side of high off east coast will bring chance pops back to the forecast Mon and Tues, but mainly for WRN Panhandle and SRN Al. With southerly flow, we will begin trending towards warmer temps with highs into the mid 90s and lows near 70. && .AVIATION... Low cigs at or below 1000ft expected at all terminals as well as patchy fog. Ceilings will lift to VFR during the day and thunderstorms are expected tomorrow in the late afternoon/early evening for northern terminals DHN and ABY, and in the evening for TLH, ECP, and VLD. && .MARINE... Moderate west to southwest winds will continue through Wednesday as a cold front approaches from the north and stalls. As this front dissipates Wednesday night and Thursday, winds and seas will subside to more typical summer time levels. However, scattered to numerous showers and thunderstorms are expected over the marine area through Thursday. && .FIRE WEATHER... A frontal boundary will slowly move into the area and stall over the area through Thursday. In addition, several disturbances will move across the area. This combination will maintain a moist and unstable weather pattern with scattered to numerous showers and thunderstorms each day. Some storms will likely be strong to severe. Therefore the humidity will remain well above critical levels and no red flag concerns are anticipated through the upcoming weekend. && .PRELIMINARY POINT TEMPS/POPS... Tallahassee 93 72 88 71 91 / 40 60 60 40 40 Panama City 89 74 87 73 88 / 40 60 60 30 40 Dothan 92 71 90 70 93 / 60 60 50 30 30 Albany 92 71 88 68 92 / 60 60 50 30 30 Valdosta 93 71 88 67 90 / 60 60 60 40 40 Cross City 90 72 86 70 88 / 40 50 60 40 50 Apalachicola 89 75 86 72 85 / 40 50 60 40 50 && .TAE WATCHES/WARNINGS/ADVISORIES... AL...None. GA...None. FL...None. GM...None. && $$ |
