What is Cold Air Damming (the Wedge)?

Cold-air damming (CAD), often called “the wedge” in the Southeast, is an interesting meteorological feature that can result in tricky forecasts for meteorologists. Topography plays a major role in CAD events, and you need a mountainous range for this feature to develop. While CAD can occur in the Rockies, it is predominant east of the … Read more

DFW Snow and Sleet Totals for March 4-5, 2015 (3/4 & 3/5)

Below are details of the March 4th-5th 2015 snowstorm in North Texas. You may be interested in these related pages: DFW snowfall records dating back to 1898 List of the worst snowstorms to hit DFW (top 20) 2015 snow and sleet events (2014-2015 winter) Current snow cover map (updated daily) Daily Snowfall Accum Stats for … Read more

Atlanta: Mid 70s on Wed (3/4), Arctic front Thursday (3/5)

For a brief moment, it will feel like spring in northern Georgia.  I expect temperatures on Wednesday (3/4) to be in the lower 70s.  However, an Arctic front will move through Atlanta on Thursday morning, with temperatures falling through the 30s.  Low temperatures Friday morning (3/6) will be in the lower 20s. A lot of … Read more

Winter Storm Expected for North Texas Wednesday (3/4)

Final Update: Thursday 3/5 9 pm:  View the storm reports Discussion #6 Wednesday 3/4 at noon: ***Winter  Storm Warning is in Effect*** I have been analyzing vertical thermodynamic profiles at various times over the next 15 hours and the evolution of the atmosphere continues to support a transition from rain to freezing rain this afternoon, … Read more

Snow Expected over North Texas and DFW on Friday 2/27

Final Update Saturday 2/28: Observed Snowfall Totals The following map was prepared by the National Weather Service in Fort Worth and is a graphical representation of over 200 reports gathered via social media, storm spotters, and official observers.  I will gather additional information that will hopefully provide additional details/specifics.  All updates starting with my initial … Read more

Winter Storm Watch, Advisory, and Warning Criteria for North Texas

When it comes to winter weather, there is no shortage of advisory types.  This page is devoted to the four main winter weather products: Winter Storm Watch, Winter Storm Warning, Winter Weather Advisory, and Ice Storm Warning.  More specifically, I want to discuss the criteria used by the National Weather Service Office in Fort Worth, … Read more

Significant Winter Storm for North Texas Sun Night & Mon (2/22 – 2/23)

Overview: A winter storm is developing for North Texas. I have been monitoring the data very closely for the past few days, and my concern is growing that a problematic sleet & freezing rain event may impact the area beginning Sunday night and continuing through Monday.  On Sunday, temperatures should stay in the 40s as overcast … Read more

Rain and Colder Temperatures on the Way for D/FW

Special Update (Sunday 2/15 8:00 pm) ***Freezing Rain Possible Over Western Parts of North Texas*** ***West of a line from Gainesville to Denton to Fort Worth*** The strong cold front will move through North Texas tonight as predicted in my previous forecasts. Behind the front, temperatures will fall rapidly into the 30s. As of 8 … Read more

Atlanta: Arctic Air on the Way – Winter Precipitation Possible

Update #7  Sunday, February 15, 3:30 pm:  Warmer air will surge in earlier than expected, meaning that only rain will fall in the Atlanta metro on Monday.  Late in the day and overnight, the rain may change to freezing rain and/or sleet, especially east of a Cedartown to Douglasville to Conyers to Athens line (the … Read more

What is dynamic cooling of the atmosphere?

In atmospheric dynamics, a negatively tilted upper-level trough tends to be stronger and much more dynamic, particularly if there is a closed upper low Both rising air and heavy precipitation (especially snow) work to cool the atmosphere from the top down.  This is called dynamic cooling and it is extremely efficient at turning an otherwise … Read more

Weather Myths: Too Warm for the Snow to Stick?

Before I begin this piece, I want to present a challenge.  The following chart shows the actual high and low temperatures for a full month in Atlanta, Georgia. *A condensed version of this writeup was also featured in the Douglas County Sentinel. Challenge: Can you spot the day with a historic snowstorm? During this particular … Read more

Potentially Historic Blizzard to Impact Parts of the Northeast

Special Update (Tuesday, January 27 at 12:11 am EST):  At midnight, snowfall rates in excess of 2 inches per hour were moving west toward New York City. This band has been showing a decrease in intensity over the past couple of hours as the storm intensifies offshore and both the atmospheric energy and mesoscale forcing contract … Read more

Birmingham’s Winter Storm Watch, Warning, & Advisory Criteria for Alabama

The National Weather Service has sole responsibility for issuing weather watches and warnings.  When it comes to winter weather, there are numerous advisory types ranging from Wind Chill Advisories to Ice Storm and Blizzard Warnings.  This page is devoted to the four main winter weather products:  Winter Storm Watches, Winter Storm Warnings, Winter Weather Advisories, … Read more

DFW: Rain, windy, & colder Thursday; snow possible Thursday night

(Forecast Posted Tuesday 1/20/15) …Widespread heavy rain & possible winter weather event for North Texas… In my forecast yesterday (Monday), I noted that Thursday’s high temperature would occur at midnight (40s) then fall into the mid 30s for the daytime. This continues to be a very difficult forecast, because there isn’t a preexisting cold airmass … Read more

A Brief History of Weather Forecasting

The Weather Bureau, now known as the National Weather Service, was established on February 9, 1870 by the 41st United States Congress and signed by President Ulysses S. Grant. On March 29, 1870, the new weather forecasting service was officially assigned to the U.S. Army Signal Service within the Department of War and given the … Read more

Coldest airmass thus far will arrive in North Texas Wednesday (1/7)

I’ve been posting updates about this airmass on my Facebook and Twitter pages, but I thought I’d go ahead and write a short discussion about this airmass.  It has the potential to be the coldest air we’ve seen in a year or so, at least when measured by the low temperatures Wednesday night/Thursday morning. Precipitation … Read more

Arctic Airmass Moves into Atlanta by Wednesday (1/7)

Special Update (Wednesday, January 7 at 8 pm EST) Temperatures are already falling into the teens in the western and northern suburbs. Current temperatures are a couple of degrees colder at this hour than model guidance had indicated. Dew points (a measure of atmospheric moisture) continue to drop, and temperatures tonight should certainly be on … Read more

DFW: Freezing Rain Expected Over North Texas Tonight and New Year’s Day

Track the storm with the Weather-Net tools:  Advisories/Warnings | Live & Predictive Radar Special Update (Wednesday 12/31 11:30 pm CST) Precipitation is entering North Texas (use the radar links above to track the precipitation).  Temperatures will fall below freezing after the precipitation begins.  As I posted earlier today, the critical line is the 29º wet-bulb … Read more

Atlanta’s Winter Storm Watch, Advisory, and Warning Criteria for Georgia

As a NOAA Weather-Ready Nation Ambassador, iWeatherNet strives to create educational content to help you be prepared for any type of severe weather; this includes winter weather. I wanted to take the opportunity to briefly review the various winter weather products issued by the Atlanta National Weather Service in Peachtree City. Other States Central Alabama: … Read more

Atlanta: Heavy Rain, Strong Winds, & Severe Thunderstorms Possible

This page was updated on Tuesday 12/23 at 1:17 pm EST:  A Flood Watch has been issued Useful Tools on iWeatherNet:  Advisories | Interactive Radar Christmas Week Forecast/Event Timing: Monday/Monday Night: Rain likely. Temperatures steady in the mid 40s. Tuesday: Dense fog much of the day.  Rain and thunderstorms developing late. Rain increasing in intensity … Read more

Atlanta: Rain Likely Friday Night (12/19) & Saturday Morning (12/20)

A disturbance will bring a cold rain to the Southeast Friday night and Saturday morning (12/19 and 12/20). Simultaneously, some weak cold-air damming will be enhanced by evaporative cooling yielding a very cold/raw day for holiday shoppers, particularly during the morning.  Here are some forecast highlights for those who plan to be out and about: … Read more

DFW: Thunderstorms Expected Sunday Afternoon (12/14)

Fast moving thunderstorms will develop Sunday afternoon and should bring some much-needed rainfall to North Texas.  Below is a brief discussion of our expectations.  If you prefer, you can skip to the forecast summary. Synopsis The vigorous upper-level system that brought heavy rain and snow to portions of the Western U.S. will bring a chance … Read more

Cause of Fireworks Smoke & Fog at the ACC Championship on 12/6/14

If you watched the GA Tech/FSU ACC Championship Game in Charlotte, North Carolina tonight (12/6/14), you may have seen the smoke-filled stadium following the pre-game fireworks show.  A heavy fog was already in place, which virtually guaranteed poor visibility of the fireworks; but to make matters worse, the smoke from the fireworks had no where … Read more

Difference Between Single vs. Multiple Lake Effect Snow Bands

Radar image showing both single and multiple snow bands.

In an earlier article, we discussed the dynamics and thermodynamics of lake effect snow. In this post, we discuss the meteorological differences between single-band and multiple-band lake-effect snow events.  Keep in mind that all lake-effect snow events are fueled by moisture and latent heat flux from the relatively warm lake water; these fluxes are already … Read more

Freezing Rain Over Portions of the Appalachians through Tuesday (12/2)

The potential for freezing rain has increased for tonight through Tuesday across portions of Pennsylvania, Virginia, and West Virginia. A cold front moving through the region will allow temperatures to drop below freezing later today and into tonight. The 12Z Wilmington, Ohio sounding revealed a deep warm layer aloft; however, as the rain begins to … Read more

DFW: Quick-Hitting Arctic Front Arrives Monday Morning (12/1)

An unseasonably warm weekend is about to commence over North Texas, with temperatures in the mid to upper 70s.  That will come to an abrupt end first thing Monday morning, with the passage of a very shallow, quick-hitting Arctic front.   Temperatures Monday will be about 40 degrees colder than those of Sunday.  So, get out … Read more

Heavy Snow Impacting Holiday Travel over the mid-Atlantic & New England

Important Tools: Interactive & Predictive Radar | Weather Advisories Heavy snow is continuing across the mid-Atlantic and the Northeast as an area of low pressure moves northward along the eastern seaboard. Winter Storm Warnings are in effect for a large portion of the inland mid-Atlantic and New England.  Be sure to check road conditions along … Read more

Forecast Highlights for Thanksgiving Travelers

If you’re traveling over Thanksgiving, it will be an active holiday week across the nation. In this blog, we’ll go over some of the potential trouble spots across the country.  Below are some forecast highlights. Important Tools: Interactive & Predictive Radar | Weather Advisories Wednesday Pacific Northwest/Rockies: Rain and higher elevation snow will be likely … Read more

Atlanta: Thunderstorms and Heavy Rain Tomorrow (Sun 11/23)

For the past week, the global numerical prediction models, including the GFS and ECMWF, have hinted at the potential of a negatively tilted trough digging into the Southeast. They have consistently indicated a strong area of low pressure across the Arklatex propagating off to the northeast into Missouri and Kentucky.  Ahead of the low, an … Read more