Welcome to the 5.10 Update! This update adds the RRFS model and brings a major expansion to our Australian coverage: Australian Weather Alerts, plus a revitalized Australian radar network with new dual-pol products, additional tilts, and Bureau-standard site naming. 🧵👇🏻

A crisp autumn breeze can make it feel colder than the thermometer reads! Wind increases heat loss from exposed skin. Wind chill combines air temperature and wind speed to describe how cold it feels, helping you prepare before heading outside.

Why do leaves change color in fall? 🍂 Shorter days signal trees to prepare for winter. As green chlorophyll breaks down, yellow and orange pigments become visible. Some trees also produce red pigments called anthocyanins.

As fall progresses and colder air becomes more common, precipitation can take different forms! Whether rain, snow, sleet, or freezing rain reaches the ground depends on temperatures throughout the atmosphere, not just at the surface.

What can make a fall night cool especially quickly?

50 years ago today, an early-season snow event blanketed parts of western New York! ❄️ On October 22, 1976, heavy, wet snow brought up to 12" to Cherry Creek and 9" to Little Valley. Snow-laden tree limbs fell onto power lines, causing outages.

A Slight Risk (Level 2/5) is in place for central/eastern Arizona into western New Mexico today. Severe storms may produce large hail, damaging winds, and a few tornadoes, with the greatest threat this afternoon and evening. Isolated hail over 2" will be possible!

The Nor'easter off the East Coast has officially become Subtropical Storm Josephine! Josephine has maximum sustained winds of 65 mph and is expected to strengthen as it accelerates northeastward away from the U.S. coast over the next day or so.

⚠️ A Severe Thunderstorm Watch has been issued for portions of central and southern Arizona until 9 PM MST. Supercells may produce hail up to 2" in diameter, damaging wind gusts up to 70 mph, and a tornado or two!

NHC will initiate advisories on Subtropical Storm Josephine (formerly Invest 93L), located offshore of the East Coast, at 5:00 PM EDT.

Severe storms can strike after dark! With fewer visual cues and many people asleep, nighttime tornadoes can be especially dangerous. Keep emergency alerts enabled, have multiple ways to receive warnings, and know where you'll shelter.

TORNADO WATCH issued for portions of northern and central Arizona until 6 PM MST. Storm coverage will increase this afternoon, with supercells capable of producing a few tornadoes, hail up to 2.5", and damaging wind gusts up to 70 mph.

Typhoon Champi has maintained an impressive satellite presentation over the past few days, with a well-defined eye and organized cloud bands as it tracked past Guam and across the Philippine Sea. 🌀 This GeoColor loop captures its persistent structure.

An ENHANCED risk (level 3/5) of severe weather covers parts of Arizona today and tonight! Multiple rounds of severe storms may bring 2"+ hail, damaging winds, and a few tornadoes. Tornado potential is greatest in northwest/north-central Arizona this afternoon and early evening.

A look at the nor'easter off the Mid-Atlantic coast today 🛰️ This system may develop some subtropical characteristics over the next couple of days as it moves over the Gulf Stream before moving away from the Eastern Seaboard later this week.

SPC has outlined an Enhanced Risk (Level 3/5) for portions of Arizona tomorrow, where an unusually significant severe weather threat is expected. Large hail (potentially exceeding 2"), damaging winds, and tornadoes are all possible, with storms potentially continuing overnight.

Which fall weather threat catches you most off guard?

Absolutely incredible 3D satellite presentation of Super Typhoon Champi from the Himawari-9 target sector as it continues churning in the Philippine Sea.

A powerful nor’easter will bring prolonged coastal impacts to the Mid-Atlantic through midweek! NHC is monitoring the system for possible subtropical development later this week. Regardless of development, coastal flooding, dangerous surf, and beach erosion are expected.

Severe weather doesn't take the fall off! ⛈️ Parts of the U.S. experience a secondary severe weather season during autumn. Make sure you have ways to get alerts and know your safe place if severe weather develops.

Watch Typhoon Champi’s weekend passage near Guam in this full PGUA reflectivity loop! Champi rapidly intensified before passing about 10 miles south of Merizo early Sunday morning, local time, as a Category 4-equivalent typhoon.