Aviation and Weather In Minnesota Mike Bardou Meteorologist, Aviation Focal Point National Weather Service Chanhassen, MN Arden Berge Meteorologist In Charge NWS Center Weather Service Unit Farmington, MN

Weather Forecast Offices (WFO)

National Weather Service WFO Chanhassen, MN Located about 25 miles west of Minneapolis/St. Paul International Airport 25 full-time staff members At least 2-3 per shift

WFO Aviation Weather Services TAFs Aviation Forecast Discussion Airport Weather Warnings Ballooning Forecasts Soaring Forecasts

TAF Sites

TAF Monitoring

Center Weather Service Units (CWSU)

Center Weather Service Unit Farmington, MN Located within the City of Farmington, MN about 20 miles S of MSP airport Staffed by 4 NWS meteorologists from 5:00 am – 8:30 pm, 7 days a week.

CWSU Aviation Weather Services Provide Professional Meteorological Services to FAA Air Traffic System Accomplished with: -Center Weather Advisories, CWA (immediate hazards to aircraft) -Meteorological Impact Statements MIS (Planning Product for air traffic system) -Collaborative Convective Forecast Product, CCFP (Coordinated 6 hour Thunderstorm forecast) -In-person and telephone briefings

Tools

Typical Precipitation Making Scenarios “Panhandle Hook” Strong low that develops in the lee of the Rockies Moves northeast drawing in Gulf moisture and cold Canadian air Several mechanisms drive heavy precipitation Can produce over a foot of snow Location of heaviest snow dependent on low track “Alberta Clipper” Fast moving low that dives out of Alberta, Canada Limited moisture limits snowfall amounts to between 1 and 6 inches Strong winds and colder air build in behind it Intensity varies greatly as does path

Average Snowfall

“Panhandle Hook”

“Alberta Clipper”

Creating TAFs Wind speed and direction Visibility/obscurations Weather type Cloud base/coverage Timing of changes

Wind Speed and Direction Driven by surface pressure pattern Upper level wind pattern can also drive sfc winds Thermal processes and amount of vertical directional shear help determine gusts

Wind Speed and Direction

Visibility Radiation Fog Develops overnight with weak flow Common under high pressure Advection Fog Typical ahead of warm fronts Can occur with weak movement of warmer air over snow cover…can be prolonged Strong low level inversion develops (warm air moving over cold air) South or east component to the wind is favorable

Visibility

Satellite

Sounding

Weather (precipitation type) Need upward motion and moisture to develop precipitation Precipitation type (RA, SN, FZRA, PL…) is dependent on the vertical temperature structure through the atmosphere Depth of cold/warm layers determines if freezing/melting occur as precipitation falls to the ground

Ideal Soundings FZRAIP FZDZFZDZ or -SN

Precipitation Intensity Determines visibility reductions in falling precip Strength of upward motion and amount of moisture in the atmosphere helps determine intensity 2 to 3 miles with light snow is common 1 mile or less is common in heavy bands of snow

Ceilings Clouds typically develop as saturation occurs at a particular level Cloud base is dependent on the level that saturation occurs Thickness of cloud cover is dependent on depth of the saturated layer

Ceilings

Biggest TAF Challenges Stratus or Fog?? Both?? Slight improvements/deterioration (eg. LIFR to IFR etc.) Precipitation Type Thunderstorm coverage Thunderstorm timing

Icing

Areas Where Icing Occurs Most non-convective icing occurs in late fall through early spring Significant icing potential increased in areas of: – Cold air advection – Relative humidity greater than 65% (the higher, the more potential) – Enhanced upward vertical motion (trofs, fronts, orographic lift) Icing can occur anywhere super cooled water droplets come in contact with an aircraft surface temperature below freezing 85% of all icing conditions occur in vicinity of frontal systems

Warm Frontal Icing Icing occurs up to 300 miles ahead of surface front – If warm air is unstable, icing may be sporadic – Warm air is stable, icing continuous over an extended area

Cold Frontal Icing Icing with cold fronts usually not as widespread as icing with a warm front – Showers/thunderstorms at front may produce icing – Icing occurs along relatively narrow bands

Occluded Front Icing Icing with occluded front has characteristics of warm and cold frontal icing – Icing ahead of front normally has warm frontal characteristics – Icing behind front is normally in narrow bands

Frost Thickness of frost determined by absolute moisture in the atmosphere “Warmer” air will hold more moisture and result in thicker easier to scrape frost “Colder” air will hold less moisture and result in thinner harder to scrape frost

How You Can Help…PIREPs!! -Limited observational data above the surface -They help us with the forecast -They also help other pilots

Aviation Weather Resources

Aviation Forecast Discussion Issued by most local offices that issue TAFs Explains the reasoning behind the TAF May also indicate confidence in the forecast and potential deviations that may occur Can also help provide info for conditions between the TAF sites

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Questions??