Distribution of Flight Rules

I took a quick look at the distribution of flight rules today, focusing on Part 139 airports in the lower 48 (CONUS). Not surprisingly, most airports are VFR or MVFR, making up more than 97% of all flight rules. IFR airports made up 2.23% of the sample. Note that this is just one observation! Currently, the weather in the CONUS is pretty good, with only 3% of Part 139 airports reporting rain, and 22% reporting broken or overcast ceilings.

Low IFR in Roanoke

Roanoke Regional Airport/Woodrum Field (KROA) was featured in a recent issue of IFR Refresher because of it's LDA approaches and rugged surrounds. That LDA may come in handy, but perhaps not handy enough this morning. Currently KROA has low IFR (with a model index of 71) with winds from 150 at 4 knots, visibility 1/2 miles in light rain and fog. Overcast layer at 100. Winds favor runway 15, but the LDA is for Runway 6 and the only ILS approach is for Runwnay 33. Current pressure and density altitudes are 1175 and 4220 feet, respectively.

METAR:
KROA 041354Z 15004KT 1/2SM -RA FG OVC001 13/13 A2992

TAF:
2009/05/04 14:16
KROA 041416Z 0414/0512 15005KT 1/2SM FG OVC001
FM041500 12005KT 2SM -SHRA OVC005
FM041600 24006KT P6SM VCSH SCT012 OVC025
FM042100 27010KT P6SM BKN035
FM050100 31007KT P6SM BKN025
FM050800 VRB04KT 6SM BR OVC007

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Champaign-Urbana

This morning, University of Illinois/Willard Airport is reporting low IFR conditions with a model index of 72:

KCMI 301245Z 14014KT 1 1/4SM -RA BR BKN003 BKN015 OVC095 17/16 A2991

The winds are from 140 at 14 knots, visibility 1.25 miles in light rain and mist. Broken layer at 300, broken 1500, overcast 9500. Temperature 62.6*F, dewpoint 60.8*F, relative humidity is 94 percent. The barometric pressure is 29.91

Expect Runway 18 - pressure altitude is 794, and density altitude is 4531

IFR and Crosswinds

KGDV 291255Z AUTO 05014G21KT 5SM BKN009 OVC047 06/04 A2988

Dawson Community Airport in Glendive is currently IFR with winds from 050 at 14 knots, gusting to 21 knots, visibility 5 miles. Broken layer at 900, overcast 4700. Temperature 42.8*F, dewpoint 39.2*F, relative humidity is 87 percent. The barometric pressure is 29.88 Wind chill 35*F

Another complication is the wind. On the longest runway, RWY 12, there is a left crosswind component of 14 knots.

METAR Decoding

Here is the current base METAR for San Antonio:
KSAT 281253Z 08006KT 1/8SM R12R/2600V3000FT -RA BR VV001 19/18 A3013

The wxJabber model index is 78 and conditions are LIFR. The METAR is decoded: San Antonio reporting winds from 080 at 6 knots, visibility 0.125 miles, and vertical visibility at 100 feet in light rain and mist. The RVR for Runway 12R is variable between 2600 and 3000 feet. The temperature 66.2*F, dewpoint 64.4*F, relative humidity is 94 percent. The barometric pressure is 30.13.

Historical data reveals that conditions at San Antonio have been LIFR since at least 3:00 A.M., and the TAF indicates soggy conditions for the rest of the day:

http://flightaware.com/live/airport/KSAT/wx

Corsicana, Texas

This is not the place to fly into or out of today. Currently, Corsicana is Low IFR with CAT II: winds 290 at 22 knots, gusting to 30 knots, visibility 3/4 miles in rain and mist. Few clouds at 1000, broken 1900, overcast 2600. Thunder Storms. Temperature 64.4*F, dewpoint 60.8*F, relative humidity is 88 percent. The barometric pressure is 30.05

For information about aviation weather check out FlightAware's weather page at http://flightaware.com/resources/weather_maps/