TAF Confusion

[pchavez35]

Hi all! First post here as a new student pilot. Please help me understand this TAF…

TAF KRIC 292340Z 3000/3024 05006KT P6SM VCSH BKN070
FM300300 05004KT P6SM VCSH SCT008 OVC015
TEMPO 3003/3005 BKN008
FM300700 06004KT P6SM OVC006
FM301700 06007KT P6SM VCSH OVC015

I understand the first line is valid from 0000 to 0300 and the tempo is valid for 2 hours from 0300 until 0500… my question lies in the next 0700 line, since there is a gap of 2hrs. If we are curious about 0600, do we revert to the FM300300 (2nd line with winds 050 at 4kts) line? So outside of the TEMPO 2 hours, the weather outside 0300-0500 time period, is the first FM line?

Here’s another one. What line would we use if we are curious at 0500?

TAF KMGW 292335Z 3000/3024 10005KT P6SM OVC060
TEMPO 3000/3004 6SM -SHRA
FM300600 10005KT 5SM -RA BR OVC025
FM301500 10005KT 3SM -RA BR OVC007
FM302200 09005KT 6SM -RA OVC015

Thanks guys!

 

[dmspilot]

Hi all! First post here as a new student pilot. Please help me understand this TAF…

TAF KRIC 292340Z 3000/3024 05006KT P6SM VCSH BKN070
FM300300 05004KT P6SM VCSH SCT008 OVC015
TEMPO 3003/3005 BKN008
FM300700 06004KT P6SM OVC006
FM301700 06007KT P6SM VCSH OVC015

I understand the first line is valid from 0000 to 0300 and the tempo is valid for 2 hours from 0300 until 0500… my question lies in the next 0700 line, since there is a gap of 2hrs.

There's no gap. The FM ("FroM") line is valid until the next FM line (or, sometimes a BECMG line). The TEMPO ("TEMPOrary") line is temporary. Notice it's incomplete -- there's no wind or visibility. At 06:00Z the line "FM300300 05004KT P6SM VCSH SCT008 OVC015" is still in effect.

 

[Clip4]

Hi all! First post here as a new student pilot. Please help me understand this TAF…

TAF KRIC 292340Z 3000/3024 05006KT P6SM VCSH BKN070
FM300300 05004KT P6SM VCSH SCT008 OVC015
TEMPO 3003/3005 BKN008
FM300700 06004KT P6SM OVC006
FM301700 06007KT P6SM VCSH OVC015

I understand the first line is valid from 0000 to 0300 and the tempo is valid for 2 hours from 0300 until 0500… my question lies in the next 0700 line, since there is a gap of 2hrs. If we are curious about 0600, do we revert to the FM300300 (2nd line with winds 050 at 4kts) line? So outside of the TEMPO 2 hours, the weather outside 0300-0500 time period, is the first FM line?

Here’s another one. What line would we use if we are curious at 0500?

TAF KMGW 292335Z 3000/3024 10005KT P6SM OVC060
TEMPO 3000/3004 6SM -SHRA
FM300600 10005KT 5SM -RA BR OVC025
FM301500 10005KT 3SM -RA BR OVC007
FM302200 09005KT 6SM -RA OVC015

Thanks guys!

Adding to DM,

TEMPO group may be used if: (1) the temporary condition has greater than 50% chance of occurring; (2) the temporary condition is expected to last less than one hour for each individual occurrence; and (3) the total duration of the temporary condition is less than half the forecast period.

 

[Racerx]

For the second example you'd revert to the first line of the taf. That first line is valid up to 0600. The tempo ends at 0400 so it no longer applies at 0500. The 0600 doesn't apply as it isn't in effect yet.

 

[scottd]

or, sometimes a BECMG line

Just to note the BECMG was dropped more than two decades ago from appearing in TAFs issued by the NWS...it will appear in international and military TAFs.

 

[scottd]

Hi all! First post here as a new student pilot. Please help me understand this TAF…

TAF KRIC 292340Z 3000/3024 05006KT P6SM VCSH BKN070
FM300300 05004KT P6SM VCSH SCT008 OVC015
TEMPO 3003/3005 BKN008
FM300700 06004KT P6SM OVC006
FM301700 06007KT P6SM VCSH OVC015

I understand the first line is valid from 0000 to 0300 and the tempo is valid for 2 hours from 0300 until 0500… my question lies in the next 0700 line, since there is a gap of 2hrs. If we are curious about 0600, do we revert to the FM300300 (2nd line with winds 050 at 4kts) line? So outside of the TEMPO 2 hours, the weather outside 0300-0500 time period, is the first FM line?

Here’s another one. What line would we use if we are curious at 0500?

TAF KMGW 292335Z 3000/3024 10005KT P6SM OVC060
TEMPO 3000/3004 6SM -SHRA
FM300600 10005KT 5SM -RA BR OVC025
FM301500 10005KT 3SM -RA BR OVC007
FM302200 09005KT 6SM -RA OVC015

Thanks guys!

The way to look at this is the following...

The TAF starts out with prevailing conditions which is the first line in the TAF right after the valid period (e.g., 3000/3034). If the weather is expected to change over the 24 or 30 hour valid period, you will see other forecast groups following the prevailing conditions. If not, the TAF will end with these prevailing conditions (called a one-liner TAF). Each forecast group to follow essentially modifies or establishes a new set of prevailing conditions. FM (From) groups tell you the prevailing conditions are expected to change over a 1 hour period. BECMG (Becoming) is a more gradual change over a two hour period. NWS does not use BECMG, but you may see this in an international TAF or military TAF.

In some cases, those prevailing conditions may temporarily fluctuate. In this case, a TEMPO group will be used to indicate this. Conditions in a TEMPO group may forecast worse or even better conditions than its enclosing prevailing FM (or BECMG) group. So they "modify" the prevailing condition during its valid time period. TEMPO groups cannot be more than four hours long by NWS directives.

The other group you will see is a PROB30 group (NWS only uses PROB30). The PROB30 group is located within the same line of the prevailing condition group. These are used to quantify the uncertainty of a precipitation event that is expected during the valid time of the prevailing group it is associated with. Specifically these are used to denote a 30% chance of a thunderstorm or other precipitation event and its associated weather and obscuration elements (wind, visibility and/or sky condition) when occurrence of those elements are directly related to the thunderstorm or precipitation event. PROB30 groups cannot be more than 6 hours in length by NWS directives.