How is PlaneWX different from my EFB or aviationweather.gov?

Your EFB is excellent for charts, filing, and day-of flying. Aviationweather.gov and Flight Service (including 1800WXBRIEF) give you official weather products. PlaneWX sits beside those tools. It does not replace them. What PlaneWX adds is decision support days out: a WX Score matched to your aircraft and personal minimums, a dynamic FRAT on the FAA PAVE framework, and mentors who see the same briefing you see. You can also share a flight plan into PlaneWX from a supported EFB. You stay PIC. Charts, filing, and official sources stay where they belong.

Is the briefing accurate?

Your briefing uses the same official observations and forecasts every pilot relies on: METARs, TAFs, PIREPs, SIGMETs and model guidance. It can only be as accurate as those forecasts, and every forecast carries some uncertainty. Every weather briefing, from any provider, also has the same built-in limit. It describes one departure time, one route, one altitude and one arrival time. Real flights change. You leave late, get rerouted, or get assigned a different altitude, and each change puts you in weather the briefing didn't look at. That's why PlaneWX can keep updating your briefing for monitored flights as the forecast changes, and why your decision-making continues in the air.

How can I make my briefing more accurate?

Enter the flight the way you'll really fly it: a realistic departure time, the route you expect to file or be cleared, your planned altitude, and the right aircraft profile. If any of those change, update the trip and brief again. Check again close to departure, when the forecasts are freshest.

Yes, in specific places. Weather reports, forecasts, model data and NOTAMs are fetched and decoded by code. AI reads forecaster discussions and writes the plain-language briefing, the hazard summary and most section ratings. It also proposes a starting WX Score and some deductions, such as for convection. Ceiling and visibility are always scored by code. Within 12 hours of departure, your personal minimums and aircraft limits are checked by rule-based code, not the AI. Further out, AI also helps weigh icing and turbulence against your limits. You always make the final call.

What is the WX Score?

The WX Score is a 0-100% metric calculated against YOUR personal minimums and your specific aircraft, not generic VFR/IFR categories. It tells you, in a single number, how well conditions are expected to match your standards. Every deduction is transparent and explained.

What is the PAVE framework?

PAVE is the FAA risk framework: Pilot, Aircraft, enVironment, and External pressures. It is the structure behind a serious preflight risk assessment, not a weather product by itself. We walk through it in plain language in our PAVE risk assessment guide. PlaneWX FRAT uses that same framework as a living sit-down assessment near departure. See how PlaneWX FRAT works, including how the briefing and airport context feed the enVironment side.

How far in advance can PlaneWX forecast weather?

PlaneWX provides weather intelligence from 14 days out through departure. Confidence improves as your flight approaches. We are transparent about uncertainty at every time horizon.

What is the mentor system?

PlaneWX connects you with experienced pilots who can review your full briefing (WX Score, aircraft profile, personal minimums) and offer a second set of eyes grounded in shared data, not guesswork. Mentor sits alongside the risk-management loop when you want it.

Is there a free plan?

Yes. Free forever includes full-quality briefings. We limit how much you can use PlaneWX, not how good the analysis is. Details on plans and what each tier includes are in PlaneWX Plans help.

What's the difference between Casual, Pro, and Pro Plus?

Casual is for pilots who fly a few times a month and want auto-monitoring. Pro raises limits and automation. Pro Plus adds Ground Protection, Auto-Brief, Pre-Flight Text, briefed fuel stops, and Labs. Compare current limits and features in Plans help, or start from the pricing section on this page. Personal minimums still drive the WX Score on every plan. If you are setting those for the first time, see personal minimums for weather planning.

What happens after the 14-day free trial?

You keep access on Free, or choose Casual, Pro, or Pro Plus. No card is required to start the trial. Plan details stay in Plans help.

“An air mass is a large body of air with generally uniform temperature and humidity.” It is named for the temperature and moisture of its source region.

Fronts, Troughs, and Drylines for Pilots: Air Masses and the Weather Map

PlaneWX · Last reviewed October 3, 2026

An air mass is a large body of air with generally uniform temperature and humidity. Most of the weather that changes a cross-country plan sits on the boundaries between air masses, called fronts, and on related features such as troughs, ridges, and the dryline. Warm fronts typically crawl at 10 to 25 mph with widespread layered weather; cold fronts often run 25 to 30 mph with a narrower, sharper band. Reading the surface analysis chart and the Area Forecast Discussion together tells you what is advancing, how fast, and how sure the forecaster is [1, paras. 11.1, 11.3, 11.3.1, 11.3.2, and 25.2.3].

Key takeaways

Know which air masses are in play, then which boundary is moving toward you [1, paras. 11.2 and 11.3].
Time the passage. Warm-front weather is often long and layered; cold-front weather is often short and intense [1, paras. 11.3.1 and 11.3.2].
On the Plains in spring, treat the dryline as a storm trigger, not just a humidity line [1, para. 11.5].

Key facts

Air masses are large bodies of air with generally uniform temperature and humidity [1, para. 11.1].
Most weather happens at fronts, the boundaries between air masses [1, para. 11.3].
Warm fronts typically move 10 to 25 mph; cold fronts typically 25 to 30 mph, with extremes up to 60 mph [1, paras. 11.3.1 and 11.3.2].
Fronts slope over colder air; frontal lift raises the warmer air and can make clouds and precipitation [1, paras. 11.3 and 12.4.3].
A wave cyclone is a mid-latitude low that forms and moves along a front, not a tornado [1, para. 11.4].
A trough is elongated relatively low pressure or height; a ridge is elongated relatively high pressure or height [1, Table 25-2].
Clear-air turbulence is often found at and just upwind of the base of an upper trough [1, para. 19.2.3.2.1].
A dryline separates moist and dry air on the High Plains and can trigger severe storms just to its east [1, para. 11.5].
Surface analysis charts are issued eight times daily (00 through 21 UTC) [1, para. 25.2.3.1].
Front symbols point in the direction the front is moving [1, para. 25.2.2.1.3].

Hover, focus, or tap any dotted term for a definition and its official source.

Fronts, troughs, and drylines are how the big picture on the weather map becomes a go/no-go problem for a specific airport and hour. This page stays with Tier 1 FAA definitions from the Aviation Weather Handbook: how air masses form and modify, what to expect before, during, and after warm and cold fronts, how a wave cyclone evolves, what troughs and ridges are, why the dryline matters, and how those features are drawn on the surface analysis chart.

What are air masses?

“An air mass is a large body of air with generally uniform temperature and humidity.” [1, para. 11.1] The area where it forms is its source region. The longer it stays there, the more it takes on the properties of the surface below [1, para. 11.2]. Air masses are classified by temperature (arctic, polar, tropical) and moisture (continental or maritime) [1, paras. 11.2.1.1 and 11.2.1.2]. Applied together, five air masses are commonly identified:

Air mass	Properties	Source
Continental Arctic (cA)	Cold, dry [1, para. 11.2.1.3]	Arctic ice and snow surfaces, mostly in winter [1, para. 11.2.1.1]
Continental Polar (cP)	Cold, dry [1, para. 11.2.1.3]	High-latitude land [1, para. 11.2.1.1]
Continental Tropical (cT)	Hot, dry [1, para. 11.2.1.3]	Low-latitude land such as the Mexican Plateau [1, paras. 11.2.1.3 and 11.2.2]
Maritime Polar (mP)	Cool, moist [1, para. 11.2.1.3]	High-latitude water [1, para. 11.2.1.2]
Maritime Tropical (mT)	Warm, moist [1, para. 11.2.1.3]	Low-latitude water [1, para. 11.2.1.2]

As air masses move, they modify. Warm, moist air moving over a cold surface tends to become more stable, with stratiform clouds, fog, and drizzle [1, para. 11.2.2]. Lake effect is the effect of any lake in modifying the weather near its shore and for some distance downwind; in the United States the term is applied specifically around the Great Lakes (and sometimes the Great Salt Lake), where cold, dry polar air flowing over relatively warm water can produce bands of cumuliform clouds and heavy snow to the lee [1, para. 11.2.2.1].

What is a front?

“A front is a boundary or transition zone between two air masses.” Most weather occurs along the periphery of air masses at those boundaries. Fronts are classified by which air mass (cold or warm) is replacing the other [1, para. 11.3].

Fronts are usually detectable at the surface by significant temperature gradients (especially on the cold-air side), converging winds, and pressure that typically decreases as a front approaches and increases after it passes. Fronts also have vertical structure: they slope over the colder, denser air mass [1, para. 11.3].

Frontal lift is one of the main ways that lift makes clouds. “Frontal lift (see Figure 12-6) occurs when the cold, denser air wedges under the warm, less dense air, plowing it upward, and/or the warmer air rides up and over the colder air in a process called overrunning.” Clouds and precipitation form given sufficient lift and moisture in the warm air [1, para. 12.4.3].

Front type	What advances	Typical speed	What pilots often see
Warm front	Warm air replaces colder air [1, para. 11.3.1]	Typically 10 to 25 mph [1, para. 11.3.1]	Gentle slope, widespread layered cloud and precipitation ahead if the warm air is stable; thunderstorms more likely in summer [1, para. 11.3.1]
Cold front	Cold, dense air replaces warmer air [1, para. 11.3.2]	Typically 25 to 30 mph; extremes up to 60 mph [1, para. 11.3.2]	Steep slope, often a narrow band of showers and thunderstorms along or just ahead of the front if the warm air is unstable [1, para. 11.3.2]
Stationary front	Neither air mass wins, so the boundary barely moves [1, para. 11.3.3]	Little or no progress [1, para. 11.3.3]	A mix of warm-front and cold-front weather that can linger for days [1, para. 11.3.3]
Occluded front	A cold front catches a warm front and the two merge [1, para. 11.3.4]	Set by the faster cold front [1, para. 11.3.4]	Warm-front weather as it approaches, then cold-front weather; cold and warm occlusion types differ by which air is colder [1, para. 11.3.4]

What changes before, during, and after a front?

The Handbook walks through typical warm-front and cold-front sequences. Use them as a pattern check against the TAF, METAR trend, and Area Forecast Discussion, not as a fixed script for every front:

Stage	Warm front	Cold front
Before	Cirriform or stratiform clouds and fog along the boundary; light to moderate precip; south-southeast wind; cool or cold with rising dewpoint; pressure falls [1, para. 11.3.1]	Cirriform or towering cumulus, possible cumulonimbus; rain showers possible; high dewpoint; pressure falls [1, para. 11.3.2]
During	Stratiform clouds, drizzle possible; poor visibility that improves; variable winds; temperature rises; dewpoint steady; pressure levels off [1, para. 11.3.1]	Towering cumulus or cumulonimbus; heavy showers, possible lightning, thunder, hail, or tornadoes on severe fronts; poor visibility; gusty variable winds; temperature and dewpoint drop; pressure bottoms then rises [1, para. 11.3.2]
After	Stratocumulus, possible rain showers; visibility improves; south-southwest wind; dewpoint rises then levels; slight pressure rise then a decrease [1, para. 11.3.1]	Clouds ease to cumulus; precip decreases; good visibility; west-northwest wind; cooler temperatures; pressure continues to rise [1, para. 11.3.2]

Fast-moving cold fronts can pack weather into a very narrow band along the leading edge. “A continuous line of thunderstorms, or squall line, may form along or ahead of the front.” “Squall lines present a serious hazard to pilots as squall-type thunderstorms are intense and move quickly.” Behind a fast-moving cold front the skies usually clear rapidly, leaving gusty, turbulent winds and colder temperatures [1, para. 11.3.2]. For thunderstorm structure and avoidance distances, see the thunderstorms guide.

Occlusions come in two types. A cold-front occlusion occurs when the air behind the cold front is colder than the cool air ahead of the warm front, so the cold air replaces the cool air and forces the warm front aloft. A warm-front occlusion occurs when the air ahead of the warm front is colder than the air of the cold front, so the cold front rides up and over the warm front; if that lifted air is unstable, the weather can be more severe than in a cold-front occlusion, with embedded thunderstorms, rain, and fog [1, para. 11.3.4]. Radar and satellite clues for those structures are covered in the weather radar guide.

How does a wave cyclone develop?

“A wave cyclone is a low-pressure circulation that forms and moves along a front.” Wave cyclones are the primary weather producers in the mid-latitudes. They are large lows that generally travel from west to east along a front and last from a few days to more than a week [1, para. 11.4].

“A wave cyclone should not be confused with the alternative name for a tornado. They are quite different.” [1, para. 11.4 footnote]

Stage	What happens
1	A stationary front separates warm air from cold air [1, para. 11.4]
2	A low-pressure wave forms on the front; a kink develops; precipitation is heaviest in the zone of lift along the front [1, para. 11.4]
3	The wave intensifies; cold and warm fronts become better organized [1, para. 11.4]
4	A mature low forms; an occluded front develops as the cold front overtakes the warm front [1, para. 11.4]
5	The occlusion grows and cuts off the warm moist air supply; the low gradually dissipates [1, para. 11.4]

What are troughs and ridges?

On weather charts, highs, lows, troughs, and ridges are the organized pressure and height patterns pilots see on the surface analysis and upper-air charts:

Feature	Definition (Handbook Table 25-2)
Low	A minimum of atmospheric pressure in two dimensions (closed isobars) on a surface chart, or a minimum of height (closed contours) on a constant-pressure chart. Also known as a cyclone. [1, Table 25-2]
High	A maximum of atmospheric pressure in two dimensions (closed isobars) on a surface chart, or a maximum of height (closed contours) on a constant-pressure chart. Also known as an anticyclone. [1, Table 25-2]
Trough	“An elongated area of relatively low atmospheric pressure or height.” [1, Table 25-2]
Ridge	“An elongated area of relatively high atmospheric pressure or height.” May also refer to other quantities such as temperature and dewpoint [1, Table 25-2]

At the surface in the Northern Hemisphere, “the surface wind spirals clockwise and outward from high pressure and counterclockwise and inward into low pressure”. Winds diverge away from surface high pressure, favoring sinking, warming air and clearing; winds converge into surface low pressure, favoring rising, cooling air and clouds and precipitation when moisture is available [1, paras. 10.5 and 12.4.2].

Upper troughs also matter for clear-air turbulence. “CAT is found most frequently at, and just upwind of, the base of the trough, especially just downwind of an area of strong temperature advection.” “Wind shift areas associated with pressure troughs and ridges are frequently turbulent.” [1, para. 19.2.3.2.1] See the turbulence guide for how that risk is briefed and scored.

What is a dryline?

“A dryline is a low-level boundary, hundreds of miles long, and separating moist and dry air masses.” In the United States it typically lies north-south across the southern and central High Plains during spring and early summer, with moist maritime tropical air to the east and dry continental tropical air to the west [1, para. 11.5].

“The dryline typically advances eastward during the afternoon and retreats westward at night.” A strong wave cyclone can sweep it much farther east regardless of the time of day. Low-level clouds and early morning fog often prevail in the moist air, while clearer skies mark the dry side. “Severe and sometimes tornadic thunderstorms often develop along a dryline or in the moist air just to the east of it, especially when it begins moving eastward.” [1, para. 11.5]

A typical dryline passage brings a sharp drop in humidity, clearing skies, and a wind shift from south or southeasterly to west or southwesterly. Blowing dust and rising temperatures may follow in daytime passages; the changes reverse when the dryline retreats west [1, para. 11.5].

How do these features show on the weather map?

“A surface chart (also called surface map or sea level pressure chart) is an analyzed chart of surface weather observations.” It shows the distribution of sea level pressure with isobars, plus highs, lows, ridges, troughs, fronts, and boundaries such as drylines [1, para. 25.2.3]. “The WPC issues surface analysis charts for North America eight times daily, valid at 00, 03, 06, 09, 12, 15, 18, and 21 UTC.” [1, para. 25.2.3.1]

“The symbols on the front indicate the type of front and point in the direction toward which the front is moving.” Two short lines across a front indicate a change in front type [1, para. 25.2.2.1.3].

The surface chart shows where the features are. The Area Forecast Discussion (AFD) often explains why the wind or weather is changing. As the PlaneWX glossary puts it, “a TAF says the wind shifts at 18Z, the discussion says it shifts because a cold front arrives and that the forecaster is unsure of the timing.” And “PlaneWX reads the discussion for your airport’s office and quotes it directly.” (Weather & Aviation Glossary)

Where are the official fronts and troughs references?

Official fronts, troughs, and dryline references

Links checked October 3, 2026: Handbook PDF anchors resolved from the saved text.

Where do the big-picture features catch pilots?

Timing from the symbol alone. The front symbol shows type and direction of motion, not the hour it hits your airport [1, para. 25.2.2.1.3]. Pair the chart with the TAF and AFD.
Warm-front patience. Widespread layered cloud and precip can sit well ahead of the surface warm front [1, para. 11.3.1].
Cold-front compression. A fast cold front or squall line can pack the worst weather into a narrow, fast-moving band [1, para. 11.3.2].
Dryline as “just humidity.” Severe storms often fire along the dryline or just east of it when it starts moving east [1, para. 11.5].
Upper trough CAT. Clear-air turbulence is common at and just upwind of the base of a deep upper trough even when the sky looks clear [1, para. 19.2.3.2.1].

How do you use fronts and troughs in a go/no-go decision?

The decision is yours as PIC. Habits drawn from the Handbook guidance above:

Identify the air masses and the boundary. Cold versus warm versus dryline versus stationary changes what “passage” looks like [1, paras. 11.3 and 11.5].
Read before, during, and after as a sequence. Use the TAF change groups and METAR trend against the warm-front and cold-front patterns [1, paras. 11.3.1 and 11.3.2].
Treat squall lines and dryline storms as thunderstorm problems. Intense, fast-moving convection needs the thunderstorm playbook, not a casual delay [1, paras. 11.3.2 and 11.5].
Check the AFD for confidence. When the forecaster is unsure of frontal timing, build more margin into departure and alternate plans [2].
On longer legs, check the upper pattern too. A deep trough can mean CAT even away from surface weather [1, para. 19.2.3.2.1].

Where does the big picture fit in a disciplined decision?

PlaneWX is decision support for general aviation pilots, built around one idea: “Fly like it’s your job.” Treat the weather decision the way a professional crew would, with the same process every time. That process is a loop: WX Score, then FRAT, then GO / NO-GO, then Self Debrief, with a Mentor if you want one. Synoptic features feed the WX Score and the briefing narrative. Here’s how PlaneWX handles them, as its help center describes [2]:

WX Score and AFD. “PlaneWX reads the discussion for your airport’s office and quotes it directly.” (Weather & Aviation Glossary)
WX Score and WPC discussions. “WPC short-range and extended discussions are analyzed for convective language.” (Hazardous Weather)
FRAT. The flight risk assessment opens in the last 4 hours before departure (FRAT).
GO / NO-GO. “PlaneWX never recommends GO or NO-GO. You make the call as PIC.” (The Risk Loop)
Self Debrief. If a front, trough, or dryline arrived earlier or later than you briefed, note it for the next trip (The Risk Loop).

The help center is plain about the limits: “PlaneWX is not a substitute for a complete, independent pre-flight weather briefing. Pull one from a source you already trust before you fly.” (The Risk Loop)

Check the fronts and discussions on your route in a PlaneWX briefing, or read how PlaneWX uses the Area Forecast Discussion.

Frequently asked questions

What is an air mass?

“An air mass is a large body of air with generally uniform temperature and humidity.” [1, para. 11.1] It is named for the temperature and moisture of its source region [1, para. 11.2.1].

What is a front?

“A front is a boundary or transition zone between two air masses.” Most weather occurs along the periphery of air masses at those boundaries [1, para. 11.3].

How do you detect a front at the surface?

Significant temperature gradients (especially on the cold-air side), converging winds, and pressure that typically decreases as the front approaches and increases after it passes [1, para. 11.3]. Fronts also slope over the colder, denser air mass [1, para. 11.3].

How fast do warm and cold fronts move?

“Warm fronts move slowly, typically 10 to 25 mph.” [1, para. 11.3.1] “Cold fronts move more rapidly than warm fronts, progressing at a rate of 25 to 30 mph.” Extreme cold fronts have been recorded moving at speeds of up to 60 mph [1, para. 11.3.2].

What is a wave cyclone?

“A wave cyclone is a low-pressure circulation that forms and moves along a front.” Wave cyclones are the primary weather producers in the mid-latitudes [1, para. 11.4]. “A wave cyclone should not be confused with the alternative name for a tornado. They are quite different.” [1, para. 11.4 footnote]

What is a trough versus a ridge?

A trough is “An elongated area of relatively low atmospheric pressure or height.” A ridge is “An elongated area of relatively high atmospheric pressure or height.” [1, Table 25-2]

Why do troughs matter for turbulence?

“CAT is found most frequently at, and just upwind of, the base of the trough, especially just downwind of an area of strong temperature advection.” [1, para. 19.2.3.2.1] “Wind shift areas associated with pressure troughs and ridges are frequently turbulent.” [1, para. 19.2.3.2.1]

What is a dryline?

How often is the surface analysis chart issued?

“The WPC issues surface analysis charts for North America eight times daily, valid at 00, 03, 06, 09, 12, 15, 18, and 21 UTC.” [1, para. 25.2.3.1]

Does PlaneWX tell me to GO or NO-GO when a front is nearby?

“PlaneWX never recommends GO or NO-GO. You make the call as PIC.” It can quote the Area Forecast Discussion for your airport’s office and analyze WPC discussions for convective language [2].

Glossary

Every term below links to the FAA, NWS, or NOAA document that defines it. The same definitions appear when you hover, focus, or tap a dotted term on this page.

Air mass: A large body of air with generally uniform temperature and humidity, named for the region where it formed. Source: FAA Aviation Weather Handbook, 11.1
Cold front: A front where cold, dense air advances and replaces warmer air, lifting it abruptly along a steep slope. Source: FAA Aviation Weather Handbook, 11.3.2
Dryline: A low-level boundary, hundreds of miles long, separating moist air from dry air; a common trigger for severe storms on the High Plains. Source: FAA Aviation Weather Handbook, 11.5
Front: A boundary or transition zone between two air masses, where most weather happens. Source: FAA Aviation Weather Handbook, 11.3
Frontal lift: Rising air at a front, where cold air wedges under warm air or warm air rides up over cold air. Source: FAA Aviation Weather Handbook, 12.4.3
Isobar: A line on a chart connecting points of equal pressure. Source: FAA Aviation Weather Handbook, Table 25-1
Lake effect: The way a large lake changes the weather near its shore and downwind, including bands of lake effect snow. Source: FAA Aviation Weather Handbook, 11.2.2.1
Occluded front: The front that forms when a faster cold front catches up to a warm front and the two merge. Source: FAA Aviation Weather Handbook, 11.3.4
Ridge: An elongated area of relatively high atmospheric pressure or height. Source: FAA Aviation Weather Handbook, Table 25-2
Stationary front: A front that barely moves because the two air masses are about equally matched; it can affect local weather for days. Source: FAA Aviation Weather Handbook, 11.3.3
Trough: An elongated area of relatively low atmospheric pressure or height. Source: FAA Aviation Weather Handbook, Table 25-2
Warm front: A front where warm air advances and replaces colder air, usually slowly and with widespread layered cloud and precipitation. Source: FAA Aviation Weather Handbook, 11.3.1
Wave cyclone: A low-pressure circulation that forms and moves along a front; the main weather producer in the mid-latitudes. Not a tornado. Source: FAA Aviation Weather Handbook, 11.4

This page explains published FAA guidance. It is not a substitute for a current weather briefing or for instrument training. Always get a current briefing before you fly. PlaneWX never recommends GO or NO-GO; you make the call as PIC.

References

FAA‑H‑8083‑28B, “Aviation Weather Handbook.” Federal Aviation Administration, Flight Standards Service. April 2, 2026. Paragraphs cited: 10.5, 11.1 to 11.5, 12.4.2, 12.4.3, 19.2.3.2.1, 25.2.2.1.3, 25.2.3, 25.2.3.1, Table 25-2. https://www.faa.gov/regulationspolicies/handbooksmanuals/aviation/faa-h-8083-28b-aviation-weather-handbook. PDF: https://www.faa.gov/sites/faa.gov/files/FAA-H-8083-28B.pdf
PlaneWX Help Center: “Weather & Aviation Glossary,” “Hazardous Weather,” “FRAT,” “The Risk Loop,” “Turbulence Analysis.” PlaneWX. Accessed October 3, 2026. Weather & Aviation Glossary · Hazardous Weather · FRAT · The Risk Loop · Turbulence Analysis