B737 ng flight crew reported departing illegally due to weather.

Attributes
ACN	1617958
Time
Date	201902
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Make Model Name	B737 Next Generation Undifferentiated
Operating Under FAR Part	Part 121
Flight Phase	Taxi
Flight Plan	IFR
Person 1
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 339 Flight Crew Type 5500
Person 2
Function	Captain Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 415 Flight Crew Type 3000
Events
Anomaly	Deviation - Procedural FAR Deviation - Procedural Published Material / Policy

Narrative:

We had multiple issues getting the dispatch release. We continuously updated the weather via ACARS. The weather reported was -fzraplsn (light freezing rain; ice pellets; and snow). We knew that we could not take off without an allowance time for this condition. We finally got [the current] information which showed -fzrapl. We pushed back; got type I and iv deicing and taxied out. We had an allowance time of 19 minutes so we were pressed for time. ATC gave us taxi instructions to the runway and tower cleared us for takeoff. Takeoff was uneventful. Two other aircraft took off behind us. Later we learned that just before takeoff ATC changed the weather reported again to the -fzraplsn. We were not aware of this at the time. We took off with one minute remaining on the allowance time.

Original NASA ASRS Text

Title: B737 NG flight crew reported departing illegally due to weather.

Narrative: We had multiple issues getting the Dispatch Release. We continuously updated the weather via ACARS. The weather reported was -FZRAPLSN (Light freezing rain; ice pellets; and snow). We knew that we could not take off without an allowance time for this condition. We finally got [the current] information which showed -FZRAPL. We pushed back; got type I and IV deicing and taxied out. We had an allowance time of 19 minutes so we were pressed for time. ATC gave us taxi instructions to the runway and Tower cleared us for takeoff. Takeoff was uneventful. Two other aircraft took off behind us. Later we learned that just before takeoff ATC changed the weather reported again to the -FZRAPLSN. We were not aware of this at the time. We took off with one minute remaining on the allowance time.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.