Area Forecast Discussion
Issued by NWS Melbourne, FL
Issued by NWS Melbourne, FL
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
586 FXUS62 KMLB 111454 AFDMLB Area Forecast Discussion National Weather Service Melbourne FL 1054 AM EDT Tue Jun 11 2024 ...New UPDATE, MARINE... .UPDATE... Issued at 1054 AM EDT Tue Jun 11 2024 A moist airmass already in place across central Florida this morning, with morning soundings at XMR/TBW showing PW values around 2.1-2.2". PW values will continue to increase through the day, as S/SW flow continues to transport deep tropical moisture northeastward across the region. Convective coverage is isolated to scattered this morning, but some breaks in the cloud cover should ramp up shower and storm coverage through the remainder of the day, with high rain chances in place (PoPs 80-90%). Forecast rainfall totals for today into tonight range from 1-2" to the north to 2-3" to the south, with locally higher amounts of 4" or higher possible, especially in any repeated rounds of showers and storms through this afternoon and evening. This could produce minor flooding in low-lying, poor drainage, and urban areas. Additional storm threats will include lightning strikes and gusty winds up to 40 to 45 mph as low level southerly winds increase through this afternoon. This may also lead to breezy conditions along the coast from the Cape southward, with sustained speeds to 15 to 20 mph and gusts up to 25 to 30 mph possible this afternoon. Cloud cover and increasing rainfall coverage should hold max temps in the mid to upper 80s over much of the area, which are values that are near to below normal for this time of year. Still, it will be warm and muggy as dewpoints remain in the mid to upper 70s. && .MARINE... Issued at 1054 AM EDT Tue Jun 11 2024 Increased wind speeds, especially for the nearshore waters, as low level southerly flow will be on the rise through this afternoon, and should lead to sustained winds of 15-20 knots over much of the waters. Small craft exercise caution headlines are now in place for this afternoon across all waters, except nearshore Volusia. These southerly winds will remain elevated into tonight, and will have to monitor for any potential short fused upgrades to a Small Craft Advisory should winds come in a little stronger than forecast. Seas will build from 2-3 feet this morning to 3-5 feet tonight. && .PREVIOUS DISCUSSION... Issued at 525 AM EDT Tue Jun 11 2024 Today-Tonight...Atlantic ridge axis remains suppressed well to the south across the Caribbean, while to the north the stationary front meanders north and south a bit over North Florida. A weak surface disturbance forming along the boundary over or just offshore of Northeast Florida will tighten the pressure gradient across the area, building SW-S winds a bit to 10-15 mph with some gusts to 20 mph this afternoon. All the rain and cloud cover will prevent any meaningful development of the sea breeze, and keep temperatures at or below normal, generally in the M-U80s. While less hot, the very high humidity keep heat indices in the 90s. No significant change in rain chances and amounts since the afternoon forecast. PoPs 40-60 pct this morning increase to 70-90 pct this afternoon, then back off to 30-50 pct tonight, with the higher chances to the south. This results in a NW-SE oriented QPF gradient across the area ranging from 1-2" to the north to 2-3" to the south, with locally higher amounts of 4" or more possible where repeated rounds of heavy showers and storms setup. Long and skinny thermodynamic profiles characteristic of these high rainfall events show enough CAPE for occasional cloud to ground lightning, and 850mb winds 30-40 kts could lead to surface gusts up to 40 mph in heavier precipitation, but the primary storm hazard will be heavy rain. Any heavy showers or storms that become slow/stationary, like the one yesterday that produced 2-3" of rainfall in the eastern Orlando/Sanford metro and over 5" in the rural areas to the east, could produce minor flooding in low- lying, poor drainage, and urban areas. The antecedent dry conditions mean the ground will be able to handle this kind of rainfall for a time, especially if given a quiet period to soak in, but repeated rounds will eventually lead to more impactful and persistent flooding. Wednesday-Friday...The surface disturbance/low near Northeast Florida is forecast to continue developing as is pushes northeastward into the western Atlantic. The ECM is the faster solution, developing a closed low by Wednesday morning, while the GFS lags behind by about 24 hours. The ECM then gives up on the low, absorbing it into another weak frontal boundary approaching the eastern seaboard, while the GFS further deepens the low as it tracks northeast. The ECM solution would result in a further lowering of rain chances and QPF across the north half of ECFL than currently advertised as early as Wednesday, while the tighter pressure gradient across Florida between the low and the Atlantic high advertised by the GFS would continue to transport the deep tropical moisture across Florida and continue high rain chances, especially to the south. Thus far the GFS has been performing better, so going to keep the forecast leaned towards that solution for now, calling for high rain chances with continued rounds of showers and lightning storms, including during the overnight hours. Daily rainfall amounts of 1-3" with locally higher amounts of 4" remain possible, with event totals reaching 2-3" up north and 3-4" down south by Saturday morning. Occasional cloud to ground lightning and gusty winds will also remain possible with storms. Afternoon highs remain at or below normal but muggy in the M-U80s. Saturday-Monday...Model agreement might be a little better early this morning than previous days, but there`s still enough variation between models and runs to keep forecast confidence low. GFS continues to be much more aggressive with development of the low pressure system ejecting northeast off the Mid-Atlantic seaboard at this point, and a wave/disturbance/low forming in the Gulf of Mexico over the weekend (the organization and location of this feature changes from run-to-run). On the other hand, the ECM kills the low in the western Atlantic, and barely develops a wave in the Gulf. As a result, the GFS now continues rain chances for Florida while the ECM becomes drier, a flip-flop form this time yesterday. Given the low confidence, went with a blend that continues to favor the GFS given its aforementioned performance, keeping relatively high rain chances and near to below normal temperatures through the weekend and into next week, until a clearer picture comes into view. && .AVIATION... (12Z TAFs) Issued at 733 AM EDT Tue Jun 11 2024 VFR conditions become MVFR generally after 15z with increasing SHRA/TSRA at the sites thru 21z. Hi-res guidance suggests rain chances decreasing north to south 00z and beyond with VCSH left behind. IFR CIG/VIS are possible among heavier SHRA/TSRA. Winds 10-12 kt may gust up to 20 kt outside of convection, gradually veering S after 21z. Continued lower confidence in SHRA after 03z, though the highest chances remain MLB south. && .MARINE... Issued at 525 AM EDT Tue Jun 11 2024 Today-Tonight...Winds and seas generally favorable for boating close to shore, but SCT-NUM offshore moving showers and SCT lightning storms are expected through the period. Small craft should exercise caution offshore later this afternoon and overnight as conditions become poor due to increasing winds and building seas. Ridge axis of the Atlantic high remains suppressed well to the south across the Caribbean, with a stationary front draped across north Florida and into the adjacent Atlantic waters, producing SW-SSW winds 10-15 kts through the early afternoon. A surface disturbance slowly forming near/offshore Jacksonville will tighten the pressure gradient, shifting winds to the SSW-S and increasing to 15-20 kts across the offshore waters from the late afternoon and through the overnight. Seas 1-3 ft this morning increase to 3-5 ft, occasionally up to 6 ft in the Gulf Stream. Wednesday-Saturday...Subtle shifts in the position of the Atlantic ridge axis and a bit of uncertainty in the development of the disturbance/low pressure system off the southeastern seaboard decrease confidence in the surface wind forecast. Winds should generally remain Srly at 5-15 kts after they settle Wednesday afternoon, but how far SWrly or SErly winds become, and further increases to 15-20 kts, will depend on evolution of the aforementioned features. Better confidence the period will remain wet with SCT-NUM showers and SCT lightning storms moving offshore, and that while conditions could become poor, the should remain below advisory levels. Seas 2-4 ft Wednesday-Thursday settle to 1-3 ft Friday-Saturday. && .FIRE WEATHER... Issued at 525 AM EDT Tue Jun 11 2024 Increased moisture and shower and storm chances, as well as greater cloud cover will lead to near to below normal highs in the mid to upper 80s through the remainder of the week. This will keep Min RH values well above critical levels. Improvement of drought conditions will also occur across areas that receive heavier rainfall. Main concern from storms will be lightning strikes that may be able to start new fires, and gusty winds that could lead to control issues from any existing brush fires. && .PRELIMINARY POINT TEMPS/POPS... DAB 87 73 87 73 / 80 60 80 60 MCO 84 74 86 74 / 90 70 90 70 MLB 85 74 85 74 / 90 80 90 70 VRB 85 73 86 73 / 90 80 90 80 LEE 87 76 89 75 / 80 60 80 60 SFB 86 74 88 74 / 80 60 80 60 ORL 84 75 87 75 / 90 60 90 60 FPR 84 73 86 73 / 90 80 90 80 && .MLB WATCHES/WARNINGS/ADVISORIES... FL...None. AM...None. && $$ UPDATE...Weitlich AVIATION...Schaper