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Disclaimer
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About PREFLT XWIND
What it does
XWIND evaluates crosswinds at U.S. airports based on a user-defined limit within a selected search radius. Enter your home airport or origin, set a distance range and a maximum crosswind (personal limit) in knots, and XWIND checks current METAR observations and forecast data for every airport in range. XWIND then displays what appears to be within limits right now and what the forecast looks like.
How to read the results
Map pins
Green — crosswind on the best runway is below the user-defined limit
Amber — within a 2 kt buffer of user-defined limit (marginal)
Red — exceeds user-defined limit on every runway at a selected airport
Gray — no METAR available; crosswind estimated from NWS model data
Tap any airport card or map pin to access runway-by-runway crosswind values, forecast timelines, and raw METAR/TAF data.
Airport cards
KOKV
Winchester Regional
34.0 NM · RWY 14
6 ktsVFR
1234567
Border colorteal = within limit · amber = marginal (within 2 kt) · red = exceeds · gray = no live METAR
ICAO identifier4-character airport code (FAA identifier shown when no ICAO is assigned)
Airport nameformatted from FAA NASR database
Distance from origingreat-circle nautical miles from your home or origin airport
Best runwaythe open runway with the lowest crosswind component for current winds
Crosswind valuecalculated XW component on the best runway; color matches the border
Weather data comes from the Aviation Weather Center and NWS gridded forecasts, refreshed every 5 minutes. Airport and runway data is from the FAA NASR database (4,800+ U.S. airports).
PREFLT and XWIND are not substitutes for proper preflight planning or a regulatory-compliant weather briefing. Please read the , also linked in the footer. By using this site, you acknowledge and accept the disclaimer, subject to the terms of use and privacy policy.
About PREFLT
What is PREFLT
PREFLT is a suite of preflight planning tools built primarily for GA pilots and student pilots. Each tool answers a specific go/no-go question that can help improve aeronautical decision-making and assist with preflight planning. Make PREFLT one of the first stops in your preflight routine and one of the last checks before you go out to the plane.
The tools
Live
XWIND — Should I land and take off with current and forecast crosswinds? Checks current METARs, TAFs, and NWS forecast data against a set crosswind limit for every runway within a search range.
Soon
DALT — What's the density altitude at airports in range today? See where density altitude is a factor before you start or complete your planning.
Soon
RUNWY — Will available runway length be a constraint at my intended origin or destination? Compares available runway length against your calculated performance limits.
Data & sources
Weather data retrieved from the Aviation Weather Center and NWS gridded forecasts, refreshed every 5 minutes. Airport and runway data sourced from the FAA NASR database (4,800+ public-use U.S. airports).
PREFLT tools are not substitutes for proper preflight planning or a regulatory-compliant weather briefing. Please read the , also linked in the footer. By using this site, you acknowledge and accept the disclaimer, subject to the terms of use and privacy policy.
Frequently Asked Questions
Using PREFLT
Is PREFLT a substitute for a weather briefing?
No. PREFLT is a situational awareness and planning tool, not a regulatory weather briefing. Before any flight, pilots are required to obtain an appropriate regulatory-compliant briefing through, for example, 1800wxbrief.com. PREFLT data should complement your briefing and other planning tasks, not replace them.
What airports are included?
PREFLT covers 4,800+ public-use U.S. airports from the FAA NASR (National Airspace System Resources) database, the authoritative source for U.S. civil aviation data. Private airports, heliports, helipads, and seaports are not included. The dataset is updated with each NASR cycle.
Why does an airport show "No METAR"?
Many smaller airports don't operate a weather observation station. When no METAR is available, PREFLT uses NWS gridded forecast wind estimates where possible, but flight category (VFR / MVFR / IFR / LIFR) cannot be shown without an observation that includes sky condition and visibility. Treat no-METAR results as rough estimates only.
How often is weather data updated?
Weather data is fetched from official sources and cached server-side for up to 5 minutes. The home page previews refresh automatically every 5 minutes. The METAR age for an aiport is shown in the airport's detail panel, which is opened by clicking "View details" on an airport's map popup.
XWIND
What does "marginal" mean?
An airport is marginal (shown in amber) when its best-runway crosswind is within 2 knots of the limit set in the search. At a 10-knot limit, for example, airports with 8–10 kts crosswind are amber. This buffer is a heads-up that conditions are at or near your limit.
What is a personal crosswind limit?
Your personal crosswind limit is the maximum crosswind component that you're comfortable with and proficient operating in (taxi, takeoff, and landing), based on your experience, currency, and aircraft type. It's typically much lower than your aircraft's published demonstrated crosswind value and separate from any regulatory requirements. The FAA's Personal Minimums Worksheet is a good resource for establishing your minimums.
What do the flight category badges mean?
Flight categories describe ceiling and visibility from a METAR observation:
VFR — ceiling > 3,000 ft AGL and visibility > 5 SM
MVFR — ceiling 1,000–3,000 ft or visibility 3–5 SM
IFR — ceiling 500–1,000 ft or visibility 1–3 SM
LIFR — ceiling < 500 ft or visibility < 1 SM
What does variable wind (VRB) mean for crosswind?
When wind direction is variable (reported as VRB in the METAR), a precise crosswind component cannot be calculated because the wind angle relative to each runway is unknown. PREFLT shows the observed or forecast wind speed and flags the airport as variable. At very low speeds (e.g., VRB 3 kts), conditions are effectively calm on all runways.
Calculations
How is crosswind calculated?
PREFLT uses the standard trigonometric formula for crosswind and headwind components:
Crosswind = Wind Speed × sin(θ)
Headwind = Wind Speed × cos(θ)
where θ is the absolute angle between the wind direction and the runway heading, clamped to 0–90°. Because sin(θ) = sin(180° − θ), the crosswind component is identical for both ends of a runway — only the headwind component differs. Reference: aerotoolbox.com.
How is best runway selected?
PREFLT evaluates every open runway end at each airport. The crosswind component is calculated for each end using the current reported wind. The end with the lowest crosswind and no significanttailwind is designated the "best runway" and shown on the airport card. When winds are calm or fully variable, no preferred end is designated — any runway is equally valid.
When multiple parallel runways share the same heading (e.g., 19L, 19C, 19R), they are grouped into a combined designation since their crosswind components are identical.
How is density altitude calculated?
Density altitude is calculated in two steps:
Step 1 — Pressure Altitude:
PA = Field Elevation + 145,366 × [1 − (QNHinHg / 29.92)0.190284]
Step 2 — Density Altitude:
DA ≈ PA + 120 × (OAT − TISA)
where TISA = 15 − (0.00198 × PA) °C is the ISA standard temperature at that pressure altitude. A full calculation also incorporates humidity via water vapor partial pressure for greater accuracy at high dew points. Reference: aerotoolbox.com.
Data & Sources
Where does weather data come from?
PREFLT uses two main sources: the Aviation Weather Center (AWC) for METARs and TAFs, and NWS gridded forecasts as a supplementary or fallback source when TAF data isn't available. Data is fetched and cached every 5 minutes.
Where does airport and runway data come from?
Airport and runway data is sourced from the FAA NASR (National Airspace System Resources) database — the authoritative source for U.S. civil aviation. It includes runway dimensions, headings, surface types, elevations, and operational status for 4,800+ public-use airports. The dataset is updated with each 28-day NASR cycle.
