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Show Area Forecast Discussion - Tallahassee, FL (TAE) (Florida Panhandle) Selection: |
| #535724 (Received by flhurricane at: 9:02 PM 20.Aug.2012) AFDTAE AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 856 PM EDT Mon Aug 20 2012 ...Additional heavy rain possible overnight... ...Flash Flood Watch continues overnight for most north Florida zones... .NEAR TERM [Tonight]... While the extent and intensity of the rainfall has diminished across the region this evening, there is still the potential for additional convective development overnight. 00Z surface analysis continues to show a stationary trough/front running from central South Carolina southwest to a weak 1011mb low over Louisiana. Aloft, an unusually deep trough remains in place over the eastern CONUS, with a continuing series of shortwaves moving through the base. The next shortwave is forecast to approach the forecast area after midnight tonight. Given the existing surface trough and moist atmosphere, the approaching shortwave should trigger another round of showers and thunderstorms, primarily impacting areas south and west of a line from Panama City to Tallahassee to Valdosta. These areas could see an additional couple of inches of rain overnight on already saturated soils. Therefore, the Flash Flood Watch was continued. However, with less rain expected over the inland panhandle, the watch was dropped for this area for the remainder of the overnight. && .SHORT TERM [Tuesday Through Wednesday Night]... The axis of the persistent upper level trough will slide further east through the period. Meanwhile, a wave is forecast to track along the stationary front near Pensacola northeastward into the Carolina`s by Wednesday with the front forecast to be roughly from Tifton, Ga southwest to Panama City by late Wednesday. The result will be a gradual decrease in showers and thunderstorms as much drier air filters into the region, especially in the mid levels. PoPs for Tuesday will be tapered from low end chance northwest to likely southeast. Then will taper PoPs from silent 10% for northern tier GA and SE AL zones to good chance southeast Big Bend. Along with the expected decrease in convection and cloudiness, we will see max temps return to near seasonal levels both days. && .LONG TERM [Thursday through Monday]... Although the highly amplified mid-upper level trough present over the eastern US in the short term period will dissipate and weaken by Thursday, we are likely to remain in a weakness in the subtropical ridge through the weekend. 500mb heights are forecast by the GFS to be about 1 standard deviation below normal for much of the extended period. Meanwhile, a low level ridge axis along the length of the eastern seaboard is likely to keep flow E-NE, with a stalled front lingering near the southern part of our local forecast area, or just to the south. This general scenario was depicted well by the 19.18z suite of HPC Guidance so that was incorporated into the new extended forecast, blended with 19.12z ECMWF and 19.00z ECMWF MOS. The end result with slightly lower heights and thicknesses, as well as ENE flow in the low-levels, should be temperatures slightly below climatology with drier conditions day-to-day than what we have seen recently. This is very consistent with the forecast from last night, and thus there have only been minor tweaks to the previous forecast beyond Thursday with this grid update. && .AVIATION [Beginning 00Z Tuesday]... Fairly messy conditions are expected overnight and into Tuesday with multiple cloud decks and areas of rain. MVFR to IFR conditions are expected at all sites by late tonight, but they should be most prevailing at KECP, KTLH, and KVLD. The greatest chance of rain is also at those three sites. && .MARINE...Modest southwesterly flow is still anticipated overnight as the pressure gradient tightens over the waters south of a stationary front. Although winds may approach 15 knots late tonight, no headlines are anticipated. && .FIRE WEATHER... High values of RH over the next couple of days, coupled with wet fuels should alleviate fire weather concerns. && .TAE WATCHES/WARNINGS/ADVISORIES... FL...FLASH FLOOD WATCH until 8 AM EDT /7 AM CDT/ Tuesday FOR FLZ012>019-026>029-034-108-112-114-115-118-127-128-134. GA...None. AL...None. GM...None. && $$ NEAR TERM...Camp |
| #535671 (Received by flhurricane at: 3:05 PM 20.Aug.2012) AFDTAE AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 258 PM EDT Mon Aug 20 2012 ...Periods of heavy rain possible through tonight... ...Flash Flood Watch continues overnight for our north Florida zones... .NEAR TERM...[Tonight] A weak surface trough continues to be the focus for widespread convection across the Florida zones this afternoon. Some of the rain has been heavy and a Flash Flood Watch continues in effect for all Florida zones through 7 am Tuesday. Radar estimates 1 to 3 inches of rain has fallen over a large portion of the watch since this morning mainly along and south of I-10 with isolated amounts up to 3 to 4 inches. Further to the north, convection has begun to develop along a cold front that stretched west to east across central AL and GA. This front will be sagging southward into our northern tier GA zones extending southwestward into the western Florida panhandle by daybreak. Will keep at least likely PoPs in the forecast for the overnight hours with lows in the lower 70s most areas. && .SHORT TERM...[Tuesday through Wednesday] The axis of the persistent upper level trough will slide further east through the period. Meanwhile, a wave is forecast to track along the aforementioned cold front near Pensacola northeastward into the Carolina`s by Wednesday with the front forecast to be roughly from Tifton, Ga southwest to Panama City by late Wednesday. The result will be a gradual decrease in showers and thunderstorms as much drier air filters into the region, especially in the mid levels. PoPs for Tuesday will be tapered from low end chance northwest to likely southeast. Then will taper PoPs from silent 10% for northern tier GA and SE AL zones to good chance southeast Big Bend. Along with the expected decrease in convection and cloudiness, we will see max temps return to near seasonal levels both days. && .LONG TERM [Wednesday Night through next Monday]... Although the highly amplified mid-upper level trough present over the eastern US in the short term period will dissipate and weaken by Thursday, we are likely to remain in a weakness in the subtropical ridge through the weekend. 500mb heights are forecast by the GFS to be about 1 standard deviation below normal for much of the extended period. Meanwhile, a low level ridge axis along the length of the eastern seaboard is likely to keep flow E-NE, with a stalled front lingering near the southern part of our local forecast area, or just to the south. This general scenario was depicted well by the 19.18z suite of HPC Guidance so that was incorporated into the new extended forecast, blended with 19.12z ECMWF and 19.00z ECMWF MOS. The end result with slightly lower heights and thicknesses, as well as ENE flow in the low-levels, should be temperatures slightly below climatology with drier conditions day-to-day than what we have seen recently. This is very consistent with the forecast from last night, and thus there have only been minor tweaks to the previous forecast beyond Thursday with this grid update. && .AVIATION [through 21z Tuesday]... Persistent active weather will hold across the FL panhandle, northern FL and far southern GA. Prevailing MVFR and occasional IFR conditions will need to be expected for KECP, KTLH and KVLD for the rest of today through much of the day tomorrow, although there may be breaks VFR. For KDHN and KABY VFR conditions should hold for much of the afternoon and this evening, before conditions deteriorate later tonight into Tuesday. Beyond Tuesday, VFR conditions should return. && .MARINE... The pressure gradient will tighten as a cold front sags southward toward the waters tonight into Tuesday elevating winds and seas but staying below cautionary levels. Winds diminish to typical summertime levels Wednesday through at least the remainder of the work week. && .FIRE WEATHER... High values of RH over the next couple of days, coupled with wet fuels should alleviate fire weather concerns. && .PRELIMINARY POINT TEMPS/POPS... Tallahassee 71 88 71 89 68 / 60 60 30 40 20 Panama City 73 88 73 88 73 / 60 50 20 40 30 Dothan 69 87 69 89 69 / 50 40 10 20 20 Albany 70 87 69 89 68 / 50 50 20 30 20 Valdosta 70 87 68 88 68 / 60 70 30 40 20 Cross City 72 85 71 88 70 / 60 70 40 50 30 Apalachicola 74 88 74 87 70 / 60 60 30 50 20 && .TAE WATCHES/WARNINGS/ADVISORIES... AL...None. GA...None. FL...Flash Flood Watch through Tuesday morning for all zones. GM...None. && $$ |
| #535623 (Received by flhurricane at: 10:32 AM 20.Aug.2012) AFDTAE AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 1027 AM EDT Mon Aug 20 2012 .NEAR TERM [Through Tonight]... Morning surface analysis indicates leading surface boundary, reinforced by surface outflow from convection, extends from nern FL/sern GA southwestward between AAF and PAM. North of this boundary primary surface cold front continues to sag southward from central SC into srn MS. Leading boundary continues to maintain primary focus for widespread showers and tstms this morning, and will likely remain the main focus through the day. Given abundant moisture with PWs in excess of 2" this AM and even modest heating, heavy rainfall will remain a distinct threat and FFA across northern FL counties seems warranted. Shear is unseasonably strong this morning with 12z TLH sounding indicating 35-40 kt of deep layer shear. Although lapse rates remain very weak, and limited heating/instability are expected, shear will support a risk of organized convection in the form of small lines or even supercells. Isolated damaging winds may occur with any stronger storm, with primary threat over eastern portions of the Big Bend where heating along and south of surface boundary will be more pronounced today. Leading activity will continue shifting ewd across the Bend region through the rest of the morning, and wrn FL panhandle counties may see a bit of a break early this afternoon as leading wave pulls east and activity along the boundary well offshore sags south. However, all the area could see development again overnight and into Tuesday. && .AVIATION [Beginning 14Z Monday]... Will maintain MVFR and localized IFR conditions this morning and into the afternoon with active showers and tstms across the region, especially near KTLH, KVLD and KECP. KECP may see conditions improve by early afternoon. More difficult forecast for KALB and KDHN as more active weather may remain just south. && .MARINE... Winds and seas will generally be near typically low summertime values today, with west-southwest winds around 10 KT and significant wave heights of 2 to 3 ft. Winds and seas will increase a bit on Tuesday, increasing to 10 to 15 KT with seas of 2 to 4 FT. && .TAE WATCHES/WARNINGS/ADVISORIES... FL...FLASH FLOOD WATCH through Tuesday morning FOR FLZ007>019- 026>029-034-108-112-114-115-118-127-128-134. GA...None. AL...None. GM...None. && $$ Evans |
| #535572 (Received by flhurricane at: 4:29 AM 20.Aug.2012) AFDTAE AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 419 AM EDT Mon Aug 20 2012 ...Periods of heavy rain possible through tonight... .SYNOPSIS... The 03 UTC regional surface analysis showed a wavy, quasi-stationary front from coastal NC, through the GA-TN border, through central MS, and into east TX. Our forecast area was within a belt of fairly light west to southwest winds, north of a subtropical ridge. Vapor imagery and upper air data showed an anomalously deep, positively-tilted trough from the Great Lakes to the northwest Gulf of Mexico, with unusually strong 500 mb winds (southwest at 35- 45 KT) over our region. Precip Water values were slightly above climatology. Area radars showed a few patches of light rain across our forecast area. && .SHORT TERM... [Today through Wednesday] The latest NWP guidance consensus is in very good agreement in forecasting a wet day today. The Convection Allowing Models (CAM) forecast a quick recovery of the marine boundary layer (which was temporarily stabilized by a cold pool from last evening`s storms) by sunrise, followed by the rapid development of a large rain area over a large portion of our forecast area sometime between mid morning and mid afternoon. The same guidance indicates a near repeat of this scenario playing out for tonight and Tuesday. As the 500 mb trough gradually begins to fill and drier air infiltrates our western zones on Wednesday, our PoP will decrease to near-average levels for this time of year, ranging from 50% in Cross City to 20% in Dothan. All of the CAM forecast isolated 6-hourly QPF totals of 5 to 6 inches today and tonight, but they differ on their exact timing and location. If realized, such rainfall could be enough to cause localized flash flooding, depending on when and where these QPF maxima occur. (For instance, 5-6 inches of rain falling in less than 6 hours in an urban area would cause flash flooding). To account for this threat we issued a Flash Flood Watch through Tuesday morning. There is also a low-end chance (5%) for strong to severe storms today, mainly from I-10 southward, and mainly from marginally damaging wind gusts of 40 to 60 MPH. Unusually strong winds aloft (at least 40 KT at 500 mb) will aid in some storm organization, possibly allowing for a few bowing segments to develop. Ironically, the main limiting factor for a more widespread severe storm threat today will likely be below-average SBCAPE (from all the expected cloud cover and rain). The SBCAPE from the mean of the CAM output is under 1000 J/kg (but higher offshore). Interestingly, the CAM guidance forecasts a couple of cells with very high, persistent updraft helicity values over our coastal waters, indicating a threat for a supercell. This could indicate at least a small threat for an isolated waterspout near the coast. .LONG TERM [Wednesday Night through next Monday]... Although the highly amplified mid-upper level trough present over the eastern US in the short term period will dissipate and weaken by Thursday, we are likely to remain in a weakness in the subtropical ridge through the weekend. 500mb heights are forecast by the GFS to be about 1 standard deviation below normal for much of the extended period. Meanwhile, a low level ridge axis along the length of the eastern seaboard is likely to keep flow E-NE, with a stalled front lingering near the southern part of our local forecast area, or just to the south. This general scenario was depicted well by the 19.18z suite of HPC Guidance so that was incorporated into the new extended forecast, blended with 19.12z ECMWF and 19.00z ECMWF MOS. The end result with slightly lower heights and thicknesses, as well as ENE flow in the low-levels, should be temperatures slightly below climatology with drier conditions day-to-day than what we have seen recently. This is very consistent with the forecast from last night, and thus there have only been minor tweaks to the previous forecast beyond Thursday with this grid update. && .AVIATION [through 06z Tuesday]... In the next 6 hours (through 12z Monday): the best chance of lower CIGS in the MVFR/IFR range will be at DHN and ABY. Nearby obs just to the north indicate low CIGS near or below 1000 ft, and NARRE probabilities of low ceilings are highest at these two terminals. Beyond 12z Monday: Showers and thunderstorms should develop again late tonight or early in the morning and overspread the area fairly early in the day. MVFR/IFR expected in the +SHRA or TS, most likely at ECP, TLH, or VLD. There is a chance for some redevelopment of TS to the north near DHN and ABY in the afternoon. && .MARINE... Winds and seas will generally be near typically low summertime values today, with west-southwest winds around 10 KT and significant wave heights of 2 to 3 ft. Winds and seas will increase a bit on Tuesday, increasing to 10 to 15 KT with seas of 2 to 4 FT. && .FIRE WEATHER... A wetting rain is expected over most of the area either Monday or Monday Night. Although some slightly lower dewpoints will be moving into the area just behind a slow-moving front later in the week, the relative humidity is unlikely to fall below critical thresholds. Additionally, recent rainfall will likely keep fuel moisture relatively high. && .PRELIMINARY POINT TEMPS/POPS... Tallahassee 86 71 87 71 89 / 90 60 60 30 40 Panama City 83 73 86 73 86 / 100 60 50 20 30 Dothan 84 69 87 69 89 / 60 50 40 10 20 Albany 85 70 87 69 89 / 60 50 50 20 30 Valdosta 85 69 86 68 88 / 90 60 60 30 40 Cross City 87 72 85 71 88 / 90 60 60 40 50 Apalachicola 83 74 85 74 86 / 100 60 60 30 40 && .TAE WATCHES/WARNINGS/ADVISORIES... AL...None. GA...None. FL...Flash Flood Watch through Tuesday morning for Calhoun-Central Walton-Coastal Bay-Coastal Dixie-Coastal Franklin-Coastal Gulf-Coastal Jefferson-Coastal Taylor-Coastal Wakulla- Gadsden-Holmes-Inland Bay-Inland Dixie-Inland Franklin- Inland Gulf-Inland Jefferson-Inland Taylor-Inland Wakulla- Inland Walton-Jackson-Lafayette-Leon-Liberty-Madison-South Walton-Washington. GM...None. && $$ |
