Area Forecast Discussion

KEY MESSAGES

Issued at 210 AM EDT Sat Oct 31 2106

- Dangerous beach conditions persist this weekend as easterly winds prolong rough surf. A High Surf Advisory is in effect from this evening through Sunday, and the risk of life-threatening rip currents remains high. Minor to moderate coastal flooding remains a threat at high tide today along the southern Treasure Coast.

- There is a Marginal Risk of excessive rainfall (level 1 of 4) for the Space and Treasure Coasts today. By Sunday and Monday, a Slight Risk (level 2 of 4) is in place along the coast. Through Monday, 1 to 3" of rain is forecast with a 5-10% chance of 5 inches or more. Turn Around, Don't Drown when encountering a flooded road.

- Boating conditions remain hazardous, particularly in the open Atlantic. Small Craft Advisories remain in effect this weekend.

DISCUSSION

Issued at 210 AM EDT Sat Oct 31 2106

-----------Synoptic Overview-----------

Mid-level ridging is parked atop the Sunshine State this morning. A broad area of above-normal H5 heights extends over the eastern half of the U.S. In the polar jet stream, a shortwave over New England is responsible for reinforcing a continental high-pressure system over the Great Lakes. In the West, a longwave trough axis sits just offshore of California. Additional shortwave energy, on the nose of the subtropical jet, is located over Texas.

By Sunday evening, the surface high should move into the Mid-Atlantic, tightening the pressure gradient over Florida yet again. Meanwhile, the mid-level shortwave currently over Texas is expected to reach the northeastern Gulf and/or Florida. Guidance has continued to trend slower with the arrival of this feature. A surface reflection, most likely in the form of a weak trough, may attempt to form over the eastern Gulf by Sunday evening. Enhanced low-level moisture convergence is anticipated to coincide with a broad area of upper-level jet diffluence, especially from Sunday night into Monday morning. During this period, total moisture (PWAT) is forecast to exceed the 90th percentile of climatology over Florida.

This disturbance is forecast to weaken by Tuesday as it crawls eastward. By Wednesday night, cluster analysis of the 30/12Z ensemble suite shows another shortwave trough axis approaching the Mississippi Valley. With additional jet stream energy on its heels, guidance suggests this trough will begin to weaken as it reaches the Southeast U.S. on Thursday. This portends a rather unimpressive cold frontal passage for Florida sometime on Thursday. Somewhat drier air is still likely to reach the state once it passes.

The subtropical jet is forecast to become quasi-zonal over the Southern U.S. late next week and into the following weekend. Global ensembles indicate a weak ridge developing near Florida, maintaining above-normal H85 (5 kft) temperatures. The next signal appears to be a southern stream trough entering the Desert Southwest next weekend. It is not expected to reach Florida until at least Monday the 9th.

-------Sensible Weather & Impacts-------

Today - Tonight...

Unfortunately, high-res guidance has struggled with the pesky band of showers that has remained over portions of the Treasure Coast the last 12 hours or so. We expect that periodic showers will continue to stream off of the Atlantic, especially for areas south of Cape Canaveral today. Rain chances range from 10-30% northwest of I-4 to 50-60% from Melbourne southward. Lightning chances remain low (<25%). Showers that repeatedly affect the same areas may drop 1-3" on a very isolated basis, so we will continue to monitor trends for localized flooding.

East-northeast winds increase a bit today as the gradient tightens up. Expect occasional gusts from 20-30 mph this afternoon. This will continue to generate rough surf and numerous, life-threatening rip currents at Atlantic beaches. A High Surf Advisory will go into effect at 5 PM today. Please refrain from entering the ocean. Minor to moderate coastal flooding is also expected with the midday high tide mainly from near St. Lucie Inlet and points southward into Martin County.

Warm and muggy today with highs in the low/mid 80s.

Sunday - Monday...

As mentioned in the overview, several factors favor widespread coverage (60-80%) of showers with a few storms (20-30%). Sunday may not be a washout for all of the area, however, as the disturbance responsible for the active weather is moving in a bit slower. We anticipate the greatest areal coverage of rain sometime later Sunday through midday Monday.

The influx of energy and moisture, combined with frictional convergence and some instability emerging off the Atlantic, favor the I-95 corridor for training bands of heavy rain. To make matters worse, much of the Treasure Coast is nearly saturated from recent rains. Through Monday night, most likely rainfall tallies of 1 to 3 inches are forecast for much of east central Florida, with a 5-10% chance of localized 5" or greater totals. Where these higher amounts fall in a shorter timeframe, flash flooding could result.

Easterly winds will be strongest on Sunday, with gusts up to 30 mph. The High Surf Advisory remains in effect on Sunday at all Atlantic beaches of Central Florida. Additionally, another round of minor coastal flooding is forecast south of St. Lucie Inlet with the early afternoon high tide cycle, especially on Sunday. The high risk of life-threatening rip currents will persist into early next week.

Tuesday - Thursday...

Onshore flow should steadily weaken through midweek, but above-normal moisture is forecast to remain in place. Shower chances will continue, with 30-40% coverage expected. Storm chances remain low, at 20% or less. A cold front is slated to get here sometime on Thursday or Thursday night, albeit on a weakening trend. A thin line of showers and isolated storms may accompany the boundary. Severe weather potential still looks quite limited.

Remaining warm, with highs in the low/mid 80s.

Friday - Next Weekend...

There is some disagreement with how much dry air will be advected over Florida behind the cold front late this week, and appreciable cold advection should be stymied by progressive zonal flow. The favored scenario is a clean enough frontal passage for mostly dry, pleasant weather during this timeframe. Warm afternoons and somewhat cooler nights would prevail.

MARINE

Issued at 210 AM EDT Sat Oct 31 2106

As continental high pressure drifts into the Northeast U.S. this weekend, the pressure gradient tightens again over Florida and the adjacent local Atlantic. Fresh easterly breezes and rough seas will result in hazardous boating conditions through at least Sunday night, with a slow improvement beginning Monday into Tuesday. A disturbance approaching from the Gulf is expected to spark numerous showers and isolated storms from Sunday into Monday.

Small Craft Advisories continue for all but the nearshore Volusia waters this morning, but even that zone will go beneath the advisory by this afternoon. ENE winds 15-25 kts by this afternoon, lasting through Sunday. Seas building to 6-9 ft from this afternoon into Sunday as well. By Monday, seas slowly subside to 5-7 ft as E winds taper to 15-20 kt.

AVIATION

(18Z TAFs) Issued at 141 PM EDT Sat Oct 31 2026

A weak east coast sea breeze is enhancing onshore flow a bit this afternoon, producing winds around 15 kts gusting to around 25 kts. ISO-SCT SHRA have develop in this flow, producing brief MVFR CIGS and IFR VIS reductions. Guidance is indicating a loosely organized and persistent band of SHRA may develop across portions of ECFL from later this afternoon into the overnight. Keeping with VC mention at most TAFs, but have continued or added TEMPOs/PROB30s at KTIX- KSUA with some timing adjustment due to chances for more frequent/prolonged impacts. Winds ease to 8-13 kts overnight, closer to the higher end with continued gusts to around 20 kts along the coast, then pick back up again after 14Z Sunday. ISO-SCT SHRA forecast to continue into Sunday morning, the SHRA become SCT-NUM with ISO TSRA after 14Z.

PRELIMINARY POINT TEMPS/POPS

MLB WATCHES / WARNINGS / ADVISORIES

FL...High Surf Advisory from 5 PM this afternoon to 7 PM EDT Sunday for FLZ141-154-159-164-347-447-647-747.

Coastal Flood Advisory until 7 PM EDT Sunday for FLZ159-164.

AM...Small Craft Advisory until 7 AM EDT Monday for AMZ550.

Small Craft Advisory until 7 AM EDT Monday for AMZ552-555.

Small Craft Advisory until 7 PM EDT Monday for AMZ570-572-575.