Flight crew reported departing airport late due to lack of RVR values and below minimum weather.

Attributes
ACN	1753229
Time
Date	202007
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Make Model Name	B737-700
Operating Under FAR Part	Part 121
Flight Phase	Parked
Route In Use	Vectors
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 60 Flight Crew Type 6884
Person 2
Function	Pilot Flying Captain
Qualification	Flight Crew Instrument Flight Crew Multiengine Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Deviation - Procedural FAR Deviation - Procedural Published Material / Policy Deviation - Procedural Clearance Inflight Event / Encounter Weather / Turbulence

Narrative:

ZZZ tower was closed for early morning departure. Visibility was fluctuating between 1/4 and 1/16. A takeoff alternate was needed and obtained from dispatch. We determined that 1/4 visibility was needed to takeoff because the tower was closed and automated weather did not report RVR. We pushed and taxied with the understanding that we would not takeoff until the visibility was 1/4 or better. While waiting at the end of the runway; dispatch sent an ACARS message with RVR values. As we discussed the legality of that information; the reported visibility improved to better than 1/4. We departed without incident. I don't know of any errors that were made. If we can legally take off with dispatch reported RVR; then we were only delayed an additional three to five minutes unnecessarily. There are obvious references to dispatch weather in the manual especially for arrival weather. However; it was not so obvious for this exact scenario.

Original NASA ASRS Text

Title: Flight Crew reported departing airport late due to lack of RVR values and below minimum weather.

Narrative: ZZZ Tower was closed for early morning departure. Visibility was fluctuating between 1/4 and 1/16. A takeoff alternate was needed and obtained from Dispatch. We determined that 1/4 visibility was needed to takeoff because the Tower was closed and automated weather did not report RVR. We pushed and taxied with the understanding that we would not takeoff until the visibility was 1/4 or better. While waiting at the end of the runway; Dispatch sent an ACARS message with RVR values. As we discussed the legality of that information; the reported visibility improved to better than 1/4. We departed without incident. I don't know of any errors that were made. If we can legally take off with Dispatch reported RVR; then we were only delayed an additional three to five minutes unnecessarily. There are obvious references to Dispatch weather in the manual especially for arrival weather. However; it was not so obvious for this exact scenario.

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.