Is lo (咯) valid pinyin? MDBG and Baidu provide a pronunciation of 咯 (as in the sentence-final particle indicating that something is obvious) as lo5. "lo" isn't listed on Wikipedia's pinyin table, and I thought only bo/po/mo/fo could drop the u from -uo. Is this the standard pinyin? Is "lo" pronounced the same as "luo"?
Definition

According to yabla, 'Io' is a valid pinyin.
Quoting yabla:


  咯 
  luò
  
  
  
  to cough up
  
  
  
  
    咯 
    lo
    
    
    
    (final particle similar to 了, indicating that sth is obvious)
    
    
  
  
  咯 
  gē
  
  
  
  (phonetic)


Usage

Example Usage just for that middle one(from yabla):

哟呵呵呵我们回来咯回来了回来了

yohēhēāwǒmenhuílailohuílailehuílaile

English:
Ha ha ha ha! We are back. -You are back. You are back.

Sidenotes

A pinyin table from allsetlearning:



That proves to me that lo is a valid pinyin.