Aviation and Weather In Minnesota

Mike BardouMeteorologist, Aviation Focal Point

National Weather Service Chanhassen, MN

Arden BergeMeteorologist In Charge

NWS Center Weather Service Unit Farmington, MN

Weather Forecast Offices (WFO)

National Weather Service WFOChanhassen, 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 UnitFarmington, 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

Wind Speed and Direction

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

FZRA IP

FZDZ FZDZ 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

http://adds.aviationweather.gov/pireps/java/

Aviation Weather Resources

http://adds.aviationweather.gov/tafs/

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

http://www.aviationweather.gov/testbed/afd/

http://adds.aviationweather.gov/airmets/

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http://adds.aviationweather.gov/airmets/

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Questions??