pro radar_mask_pre_mmcr, thresh

	common mask_variables, dif_sig, count_pro, levels_t, mask


	; assume the SNR comes in.  set mask=1 where snr > -20 dbz and mask=-1 where snr < -50

	for j=0,count_pro-1 do begin
		for k=0,levels_t-1 do begin
				if dif_sig[j,k] gt -10. then mask[j,k]=1
				if dif_sig[j,k] lt -30. then mask[j,k]=-1
		endfor
	endfor

	end