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\\Stormy AI\\

Agentic weather briefing

What you are reading

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This briefing is an AI-written weather analysis for my hometown of Atco, NJ. The briefing is built from current observations, National Weather Service products, radar, lightning data, and numerical model guidance. Stormy AI gathers those sources, runs deterministic meteorological diagnostics, and asks a language model to turn the evidence into the report below.

Weather Briefing — Atco, NJ 08004

  • Updated: Thursday, October 29, 2026 7:00 PM Eastern
  • Next update: Thursday, October 29, 2026 8:00 PM Eastern
  • Generated: 2026-10-29T23:03:21+00:00
  • Type: weather

Headline

Quiet, dry, and mild weather continues across Atco tonight, with a dry cold front passing Friday morning that brings a breezy northwest wind and a brief warm spike to near 73°F, followed by a cooler, dry weekend with the coolest Halloween temperatures in the upper 50s to low 60s. No precipitation is expected through at least the start of next week.

Forecast Area

The official NWS forecast for Atco is issued by the Mount Holly (KPHI) forecast office for forecast zone NJZ018 (Camden), which covers Camden County in southern New Jersey, including the Atco/Waterford Township area.

NWS forecast zone NJZ018 (Camden)

Active Alerts

No active alerts. There are no watches, warnings, or advisories in effect for Atco or Camden County. The only nearby hazard in the Mount Holly product area is a Small Craft Advisory for the northern New Jersey coastal waters (ANZ450-451) from 2 PM Friday to 2 AM Saturday — a marine product that does not apply to inland Atco.

Current Weather

It is a dry, tranquil late-October evening across Atco.

  • Surface observation: The nearest official station is Mount Holly, South Jersey Regional Airport (KVAY), about 12.1 miles from Atco, observing at 21:54 UTC (5:54 PM EDT). This automated METAR reported no temperature, dewpoint, wind, visibility, or cloud data (PWINO — precipitation-identifier sensor out of service), but did report a sea-level pressure of 30.14 inHg (1020.7 mb). Because the station's core sensors are unavailable, nearby stations fill the gap: Philadelphia (KPHL) reported 64°F/54°F dewpoint, Atlantic City (KACY) 61°F/54°F, and Millville (KMIV) 57°F/54°F — all under high pressure around 1019–1022 mb.
  • HRRR surface guidance (model, not observation) at the Atco grid point shows a temperature of 17.8°C (64°F), dewpoint 12.2°C (54°F), and surface pressure 1015.8 mb — consistent with the regional METARs.
  • Precipitation: MRMS shows no precipitation at the location or anywhere within a 30 km radius — 0.0 mm/hr, 0% coverage, and no radar echoes within 100 km. The deterministic diagnosis confirms dry conditions with high confidence (0.89).
  • Radar: The nearest NEXRAD is KTPHL (Philadelphia), only 20.3 km away, scanning at 22:54 UTC. The lowest tilt (0.4°) samples Atco at a mean beam height of just 159 m — excellent low-level coverage. Maximum reflectivity is only 36.5 dBZ (likely ground clutter or biological scatter), with a mean of −9.3 dBZ and zero gates at or above 40 dBZ. No storm structure, no velocity products of concern, and no dual-pol signatures.
  • Lightning: GOES-19 GLM detected zero flashes within 50 km over the past 10 minutes — no electrically active convection anywhere nearby.
  • Sky: Clear skies are expected tonight per the official forecast, with temperatures falling through the 50s and dewpoints near 53°F (RH climbing toward 96% overnight).

NEXRAD reflectivity

METAR station models

Current Synoptic Setup

Per the Mount Holly Area Forecast Discussion (issued 1:26 PM EDT Thursday, Oct 29):

  • Surface pattern: High pressure is shifting offshore through tonight as low pressure moves through eastern Canada. A dry cold front associated with that Canadian low will sweep through the region Friday morning. High pressure then builds back over the area through early next week.
  • Upper-level pattern: The HRRR sounding shows a classic post-trough, subsiding airmass: westerly flow aloft (500-mb wind 24.7 kt from 256°, 300-mb 26.3 kt from 265°), a very dry mid-levels (850-mb dewpoint −3°C, 700-mb dewpoint −16°C), and a deep dry layer above a shallow moist surface layer. This is consistent with ridging/northwesterly flow behind the departing trough — no upper forcing for precipitation.
  • Moisture: Precipitable water is only 16 mm (0.63 in), and the K index is a remarkably dry 2.2 — the column is essentially devoid of deep moisture.
  • Local forcing: None. The only upcoming feature is the Friday-morning dry frontal passage, which will change wind direction (SW → NW) and increase gusts, but with no moisture to work with, it produces nothing but a breeze and a slightly cooler airmass.

GFS Guidance

GFS cycle: 2026-10-29 18Z (the newest cycle containing all requested leads), with point guidance valid at 18:00 UTC each day.

Day 1 — Friday, Oct 30 (F24, valid 18Z): Surface high pressure (1018.8 mb at Atco) dominates the Mid-Atlantic behind the morning front. At 500 mb, heights are 575.5 dam with a 37-kt westerly flow and modest vorticity (8.5×10⁻⁵ s⁻¹) — a progressive westerly pattern with no closed low nearby. The 850-mb flow is a brisk 20.8-kt westerly with 55.6% RH — dry but breezy aloft, matching the forecast NW gusts to 25 mph. The 300-mb jet is a healthy 57.8 kt overhead. Point guidance: 21.8°C (71°F), dewpoint 5.4°C (42°F), no precipitation.

Day 2 — Saturday, Oct 31 (F48, valid 18Z): Strong surface ridging builds in — 1030.5 mb at Atco, winds light at 4.4 kt. The 500-mb pattern flattens (578.1 dam, 44.6-kt flow, weak vorticity 3.7×10⁻⁵ s⁻¹), and 850-mb RH collapses to 23.4% — an exceptionally dry airmass. The 300-mb jet strengthens to 68.1 kt to the north. Point guidance: 14.9°C (59°F), dewpoint −0.9°C (30°F), no precipitation — a cool, dry, sunny Halloween.

Day 3 — Sunday, Nov 1 (F72, valid 18Z): The ridge holds — 1031.6 mb, nearly calm winds (2.7 kt). 500-mb heights 578.7 dam with light 16.3-kt flow but locally enhanced vorticity (11.9×10⁻⁵ s⁻¹) — subtle shortwave energy aloft that may add cloud cover without precipitation. 850-mb RH stays dry at 24.6%. Point guidance: 15.7°C (60°F), dewpoint −0.4°C (31°F), no precipitation.

Synthesis: GFS shows a textbook quiet autumn progression — frontal passage Friday, arctic-high ridging Saturday, and a dry, weakly disturbed Sunday. Zero precipitation at all three leads.

Surface — Day 1: GFS surface day 1 guidance 500 mb — Day 1: GFS 500-mb day 1 guidance 850 mb — Day 1: GFS 850-mb day 1 guidance 300 mb — Day 1: GFS 300-mb day 1 guidance

Surface — Day 2: GFS surface day 2 guidance 500 mb — Day 2: GFS 500-mb day 2 guidance 850 mb — Day 2: GFS 850-mb day 2 guidance 300 mb — Day 2: GFS 300-mb day 2 guidance

Surface — Day 3: GFS surface day 3 guidance 500 mb — Day 3: GFS 500-mb day 3 guidance 850 mb — Day 3: GFS 850-mb day 3 guidance 300 mb — Day 3: GFS 300-mb day 3 guidance

HRRR Analysis

HRRR cycle 2026-10-29 22Z, forecast hour 0, valid 22:00 UTC (6:00 PM EDT), grid point 0.36 km from Atco.

  • Surface thermodynamics: 17.8°C (64°F) / dewpoint 12.2°C (54°F), dewpoint depression 5.5°C, surface pressure 1015.8 mb. Comfortable and dry.
  • Precipitation type: Categorical guidance is none across all types (rain, snow, freezing rain, ice pellets) — 0.0 mm/hr. Freezing level is high at 3,734 m MSL, so any precipitation that did occur would be all-liquid; winter-type concerns are irrelevant.
  • Instability: Surface-based CAPE 0 J/kg, CIN 0 J/kg — a completely stable, convection-free environment. Mixed-layer and most-unstable CAPE are also zero. DCAPE is 523 J/kg (moderate downdraft potential energy in a dry airmass, but with no storms to produce downdrafts).
  • Model sounding (HRRR-derived, not a radiosonde): LCL at 934.9 mb (~705 m AGL) — a low cloud base if any cumulus formed, but with no LFC or EL, parcels cannot be lifted to free convection. Lapse rates are modest: 4.6°C/km surface-to-3 km and 6.6°C/km in the 700–500 mb layer — near-neutral to slightly stable, no steep midlevel lapse rates. Wet-bulb zero at 2,113 m.
  • Moisture: Precipitable water 16.0 mm (0.63 in) — very dry for late October.
  • Shear: 0–1 km bulk shear 8.9 kt, 0–3 km 18.7 kt, 0–6 km 22.9 kt — moderate deep-layer westerly shear, but with zero instability it is dynamically irrelevant for storms.
  • Indices: K index 2.2 (extremely dry), Total Totals 35.9 — all thunderstorm indices point to no convective potential.
  • Profile structure: A shallow moist surface layer (60–71% RH below 950 mb) sits beneath a sharply drying column (19–38% RH from 875 mb upward) — classic post-frontal subsidence, reinforcing the clear-sky forecast.

Outlook

The Mount Holly forecast discussion is unambiguous: "Generally tranquil weather is expected to prevail through at least the beginning of next week." Key points:

  • What changed: The coastal-flooding key message was removed — that threat has passed. No other major forecast changes.
  • Short term: Mild tonight (lows upper 40s to low 50s), then the dry cold front passes Friday morning, turning the day breezy with NW winds 10–15 mph and gusts to 25 mph. Aviation discussion confirms winds shifting to NW mid-morning with gusts to ~20 kt at area airports.
  • Weekend: Cooler. Lows Friday night through Sunday night in the mid 30s to mid 40s, but forecasters note frost currently appears unlikely where the growing season continues. Coolest highs on Halloween (upper 50s to low 60s) under partly cloudy skies; Sunday partly to mostly cloudy but milder (low-to-mid 60s).
  • Longer term: The system that had potential to affect the region early next week now appears to weaken and miss the region — keeping things dry but increasing cloud cover. A few showers can't be totally ruled out midweek, but the next credible window for widespread rainfall is late next week (Thursday into Friday), when guidance suggests a more prolific system.
  • Confidence: High for the dry, quiet pattern through the weekend; moderate on the exact timing of next week's potential rain system.

Forecast for Next 3 Days

Tonight (Thu Oct 29, 7 PM – Fri 6 AM EDT)

Clear. Low around 52°F. SW wind around 5 mph. Precipitation chance 2%. Hourly guidance shows temperatures sliding from 61°F at 7 PM to 54°F by 10 PM and holding near 54°F overnight, with RH rising to 96% and dewpoints steady near 53°F — humid-feeling for a clear night, but no fog concerns indicated. Winds light SW 5 mph throughout.

Day 1 — Friday, Oct 30

Sunny and mild, high near 73°F. The dry cold front passes in the morning; winds shift SW → W → NW 5–15 mph with gusts to 25 mph per the AFD. Precipitation chance 2% (effectively zero). Hourly detail: 53°F at 6 AM, warming through 59°F at 9 AM, 67°F at 11 AM, peaking 71°F around 2 PM, then easing to 64°F by 6 PM. Dewpoints fall steadily through the day (52°F → 43°F) as the drier airmass arrives — RH dropping from 96% in the morning to ~40% by late afternoon. Friday night: Mostly clear, low around 42°F, NW wind 5–10 mph, 0% precip, temperatures falling through the 50s and 40s overnight.

Day 2 — Saturday, Oct 31 (Halloween)

Sunny and cooler, high near 62°F. Light north wind 0–5 mph under strong high pressure (GFS: 1030.5 mb). Precipitation chance 0%. Hourly detail: 43°F at 6 AM rising through 51°F at 10 AM and 58°F at noon to a 62°F peak at 3–4 PM, then falling quickly after sunset — 57°F at 6 PM, 48°F by 8 PM. Dewpoints very dry (35–37°F). Trick-or-treating conditions (5–8 PM): upper 40s to near 60°F, mostly sunny to mostly cloudy, dry, light wind — excellent, but bring a layer as temperatures drop fast after dark. Saturday night: Mostly cloudy, low around 39°F, calm wind, 0% precip.

Day 3 — Sunday, Nov 1

Partly sunny and milder, high near 64°F. Calm winds, 0% precipitation chance. Note the Daylight Saving Time change (clocks fall back 2 AM Sunday). Hourly detail: 39°F at 6 AM (coldest reading of the three-day stretch), warming through 52°F at 9 AM and 60°F at 11 AM to a 63°F peak at 2–3 PM, then 60°F by 5 PM. Mostly cloudy morning giving way to partly sunny afternoon; dewpoints 36–39°F. Sunday night: Partly cloudy, low around 41°F, 0% precip. Beyond the window, Monday reaches 67°F partly sunny (2% precip), with the next meaningful rain chance not until late next week.

Bottom Line

Atco is in a quiet, dry stretch under building high pressure: no precipitation is on radar or in any model guidance, no alerts are in effect, and the atmosphere is completely stable (0 CAPE) with a very dry column. Tonight is clear and mild (low ~52°F). Friday features the only notable weather of the period — a dry cold front bringing NW gusts to 25 mph and a warm high near 73°F before cooler air arrives. The weekend is dry and progressively cooler, with a sunny 62°F Halloween (chilly evening for trick-or-treaters, dropping into the 40s after dark) and a milder, partly sunny 64°F Sunday. The next realistic chance of widespread rain is not until late next week (Thursday–Friday), so any outdoor plans through the weekend are a go.